CALCIUM RECEPTOR-ACTIVE MOLECULES

Abstract: Method and composition useful for treating a patient having a disease characterized by an abnormal level of one or more components, the activity of which is regulated or affected by activity of one or more inorganic-ion receptor. Novel compounds useful in these methods and compositions are also provided. The method includes administering to the patient a therapeutically effective amount of a molecule active at one or more inorganic-ion receptors as an agent or antagonist. Preferably, the molecule is able to act as either a selective agonist or antagonist at a Ca<2+> receptor of one or more but not all cells chosen from the group consisting of parathyroid cells, bone osteoclasts, juxtaglomerular kidney cells, proximal tubule kidney cells, distal tubule kidney cell, cell of the thick ascending limb of Henle's loop and/or collecting duct, keratinocyte in the epidermis, parafollicular cell in the thyroid (C-cells), intestinal cell, trophoblast in the placenta, platelet, vascular smooth muscle cell, cardiac atrial cell, gastrin and glucagon secreting cells, kidney mesangial cell and mammary cell.

Description: * CALCIUM RECEPTOR-ACTIVE MOLECULES Field of the Invention This invention relates to the design, development, composition and use of novel calcimimetic molecules able to act in a manner analogous to extracellular calcium ions on cells, to calcilytic molecules which block the activity of extracellular calcium ions on cells, and to methods for their use and identification. It also relates to a novel superfamily of inorganic-ion receptors which includes, among others, calcium receptors, nucleic acids encoding such receptors, cells, tissues and animals containing such nucleic acids, antibodies to receptors, assays utilizing receptors, and methods relating to all of the foregoing. Background of the Invention The following description provides a summary of information relevant to the present invention. It is not an admission that any of the information provided herein is prior art to the presently claimed invention, nor that any of the publications specifically or implicitly referenced are prior art to that invention. Certain cells in the body respond not only to chemical signals, but also to ions such as extracellular calcium ions (Ca 2+). Changes in the concentration of extracellular Ca (referred to herein as "[Ca + ]") alter the functional responses of these cells. One such specialized cell is the parathyroid cell which secretes parathyroid hormone (PTH) . PTH is the principal endocrine factor regulating Ca 2+ homeostasis in the blood and extracellular fluids. PTH, by acting on bone and kidney cells, increases the level of Ca 2+ in the blood. This increase in [Ca2+] then acts as a negative feedback signal,depressing PTH secretion. The reciprocal relationship between [Ca 2+] and PTH secretion forms the essential mechanism maintaining bodily Ca 2+ homeostasis. Extracellular Ca 2+ acts directly on the parathy roid cell to regulate PTH secretion. The existence of a parathyroid cell surface protein which detects changes in [Ca 2+] has been suggested. This protein acts as a receptor for extracellular Ca 2+ ("the Ca2+ receptor"), and is suggested to detect changes in [Ca 2+] and to initiate a functional cellular response, PTH secretion. For example, the role of Ca 2+ receptors and extracellular Ca 2+ m the regulati•on of m• tracellular Ca2+ and cell function is reviewed in Nemeth et al. , 11 Cell Calcium 319, 1990; the role of Ca 2+ receptors m parafollicular and parathyroid cells is discussed in Nemeth, 11 Cell Calcium 323, 1990; and the role of Ca 2+ receptors on bone osteoclasts is discussed by Zaidi, 10 Bioscience Reports 493, 1990. Other cells in the body, specifically the j osteoclast in bone, the juxtaglomerular, proximal tubule cells in the kidney, the keratinocyte in the epidermis, the parafollicular cell in the thyroid, intestinal cells the trophoblast in the placenta, have the capacity to sense 2+ changes in [Ca ] . It has been suggested that cell surface Ca 2+ receptors may also be present on theεe cells, imparting to them the ability to detect and to initiate or 2+ enable a response to changes in [Ca ] . In parathyroid cells, osteoclasts, parafollicular cells (C-cells), keratinocyteε, juxtaglomerular cellε and trophoblasts, an increase in [Ca 2+] evokes an increase in 2+ 2+ intracellular free Ca concentration ("[Ca ]^")- Such an increase may be caused by influx of extracellular Ca 2+ or by mobi.li.zation of Ca2+ from mtracellular organelles. Changes in [Ca 2+]• are readily monitored and quantitated using fluorimetric indicatorε such aε fura-2 or indo-1 (Molecular Probes, Eugene, OR). Measurement of [Ca 2+]• provides an assay to asεeεε the ability of moleculeε to act aε agonists or antagonists at the Ca 2+ receptor. In parathyroid cellε, increaεeε in the concentration of extracellular Ca 2+ evoke rapid and tranεient increaεes in [Ca 2+]. which are followed by lower yet sustained increaseε in [Ca 2+] .. The tranεient increaseε in [Ca 2+]. ariεe from the mob 1 ilization of mtracellular Ca 2+, whereaε the lower, sustained increases reεult from the influx of extracellular Ca 2+. The mobilization of mtracellular Ca 2+ lε accompanied by i. increased formation of inoεitol-l,4,5-trisphosphate (IP_) and diacylglycerol, two biochemical indicators which are associated with receptor-dependent mobilization of mtracellular Ca 2+ in various other cells. In addition to Ca 2+, various other di- and trivalent cations, such aε , and Gd 3+ alεo cauεe the mobilization of mtracellular Ca 2+ in parathyroid cellε. Mg2+ and La3+ also increase the forma tion of IP,; all these inorganic cationε depreεε the εecretion of PTH. The postulated Ca 2+ receptor on the parathyroid cell is therefore promiscuous because it detects a variety of extracellular di- and trivalent cations. The ability of various compounds to mimic extracellular Ca 2+ in vitro is discuεsed by Nemeth et al. , (spermine and spermidine) in "Calcium-Binding Proteinε in Health and Diεeaεe", 1987, Academic Preεε, Inc., pp. 33-35; Brown et al., (e.g. , neomycin) 128 Endocrinology 3047, 1991; Chen et al . , (diltiazem and itε analog, TA-3090) 5 J. Bone and Mineral Res. 581, 1990; and Zaidi et al. , (verapamil) 167 Bioche Biophys Reε Comm 807, 1990. Brown et al., 6 J. Bone and Mineral Res. 11, 1991 discuss the existing theories regarding the effects of Ca 2+ ions on parathyroid cellε, and propose that the reεultε may be explained by both a receptor-like mechaniεm and a receptor-independent mechaniεm aε follows: Polyvalent cationε [e.g., divalent and trivalent cationε] exert a variety of effectε on parathyroid function, such as inhibition of parathyroid hormone (PTH) secretion and cAMP accumulation, εtimulation of the accumulation of inoεitol phoεphateε, and elevation of the cytoεolic calcium concentration. Theεe actionε are thought to be mediated through a "receptor-like" mechanism. The inhibition of agonist-εtimulated cAMP accumulation by divalent and trivalent cationε, for example, iε blocked following preincubation with pertuεεiε toxin. Thuε, the putative polyvalent cation receptor may be coupled to inhibition of adenylate cyclaεe by the inhibitory guanine nucleotide regulatory (G) protein, G^. We recently showed that the polycationic antibiotic, neomycin, mimics the actions of di- and trivalent cations in several aεpectε of parathy roid function. To determine whether theεe actions were εpecific to thiε agent or represented a more generalized action of polycations, we teεted the effectε of the highly baεic peptideε, polyarginine and polylyεine, aε well aε protamine on the same parameters in dispersed bovine parathyroid cellε. The resultε demonstrate that the parathyroid cell respondε to a variety of polycationε aε well aε to polyvalent cationε, potentially via εimilar biochemical pathwayε. These resultε are discussed in terms of the recently postulated, "receptor-independent" modulation of G proteins by polycations in other syεtemε. The Ca 2+ receptor haε been preεumed to be analogous to other G protein-coupled receptors [e.g., a glycoprotein] , but recent studieε with other cell typeε have raiεed the poεεibility that polycationε can modulate cell function by alternative or additional mechaniεms. In mast cellε, for example, a variety of amphipathic cationε, including maεtoparan, a peptide from waεp venom, 48/80, a synthetic polycation, and polylysine, enhance εecretion by a pertussiε - 6 - toxin-sensitive mechanism, suggesting the involvement of a G protein. No classic cell surface receptor has been identified that could mediate the actions of these diverse agents. Furthermore, these same compounds have been shown to activate directly purified G proteins in solution or in artificial phospholipid veεicleε. On the baεiε of these observationε, it haε been proposed that amphipathic cations activate G proteins and, in turn, mast cell secretion by a "receptor-independent" mechanism. Polycations have also been shown to interact strongly with acidic phospholipids. Polylysines of varying chain lengths (20-1000 amino acids) bind to artificial phospholipid vesi cles with diεsociation constants in the range of 0.5 nM to 1.5 μM. The binding affinity is directly related to the length of the polylysine chain, with polymerε of 1000 amino acids having a K3 of 0.5 nM, εhorter polymerε having higher Kd values, and lysine not interacting to a significant extent. This relationship between potency and chain length is similar to that observed for the effects of polylysine 1 0, 2 00 ' polylyεine 38 0 0 ' anα ^ lysine on parathyroid function. It is posεible that the binding of polycations to biomembranes produces some of their biologic actions. The permeabilization of the plasma membrane induced in some cell types by a variety of pore-forming agents, including polycations, has been postulated to be mediated by their interaction with a phosph atidylserine-like εtructure. In addition, the "receptor-independent" activation of purified G proteinε by amphipathic cations is potentiated when these proteins are incorporated into phospholipid vesicles. Calcium ions, in the millimolar concentration range, also produce marked changes in membrane structure. In some cases, calcium can either antagonize or - 1 - potentiate the interaction of polycations with membrane lipids. Theεe conεiderationε raise the possibility that the actions of both polyvalent cations and polycations on parathyroid cells could involve a receptor-independent mechanism not requiring the presence of a clasεic, cell εurface, G protein-coupled receptor. Further εtudies, however, are required to elucidate the molecular basis for Ca 2+ senεing by thiε and other cell typeε. [Citationε omitted.] Shoback and Chen (6 (Supplement 1), J. Bone and Mineral Res. 1991, S135) and Racke et al . (6 (Supplement 1), J. Bone and Mineral Res. 1991, S118) describe experiments which are said to indicate that a Ca 2+ receptor or Ca2+ sensor is present in parathyroid cellε. Meεεenger RNA iεolated from such cells can be expresεed in oocyteε and caused to provide those oocytes with a phenotype which might be explained by thee pprreeεεeennccee ooff aa CCaa 2+ rreecceeptor protein Summary of the Invention Applicant haε demonstrated that Ca 2+ receptor proteins enable certain εpecialized cellε involved in bodily Ca 2+ metaboliεm to detect and reεpond to changeε in the concentration of extracellular Ca 2+. Although these receptors share certain general characteriεticε, they can be εelectively affected by different pharmacological agents. Aε detailed below, certain molecules are identified with εelective acti .vi.ty on Ca2+ receptorε at parathyroid cellε, oεteoclaεtε, and C-cells. Ca 2+ receptorε conεtitute discrete molecular targets for a new clasε of moleculeε that mimic ("calcimimeticε") or antagonize ( "calcilyticε") the actionε of extracellular Ca 2+. Such receptorε are preεent on cell 2+ surfaces and have a low affinity for extracellular Ca (apparent K, generally greater than about 0.5 mM) . Such receptors may include a free or bound effector mechanism, as defined by Cooper, Bloom and Roth, "The Biochemical Basis of Neuropharmacology", Ch. 4. Such receptors are thuε diεtinct from mtracellular Ca 2+ receptorε, e.g. , calmodulin ainndd the troponinε. Calcimimetics, for example, act on Ca2+ receptorε selectively to directly or indirectly depress the function of parathyroid cells or osteoclasts or to stimulate the function of C-cells. Calcimimetics and calcilytics of this invention allow novel therapies for hyperparathyroidiεm, oεteoporosis and other Ca 2+-related diseases. This application concerns in one aspect targeting Ca 2+ receptors on each of these three cell types and other cell types that detect and respond to changes in [Ca 2+] . Applicant lε the firεt to demonεtrate a Ca 2+ receptor protein in parathyroid cellε, and to pharmaco- logically differentiate such Ca 2+ receptorε in other cells, such as C-cells and osteoclasts. Applicant is also the first to deεcribe methods by which moleculeε active at theεe Ca 2+ receptorε can be identified and uεed aε lead molecules in the diεcovery, development, deεign, modification and/or conεtruction of uεeful calcimimeticε or calcilytics which are active at Ca 2+ receptors. Such calcimimetics or calcilytics are uεeful in the treatment of variouε diεease stateε characterized by abnormal levelε of one or more componentε, e.g. , polypeptideε εuch aε hormoneε, enzymes or growth factors, the expresεion and/or secretion of which is regulated or affected by activity at one or more Ca 2+ receptors. Further, the identification of different Ca 2+ receptors in different cell types, and the εpecific response of εuch receptors to different lead molecules allows design and construction of specific molecules active in treatment of specific diseases which can be affected by action at εuch εpecific Ca 2+ receptorε. For example, abnormal levels of parathyroid hormone εecretion can be affected by εuch specific molecules without affecting the lleevveell ooff secretion of other Ca 2+ regulated hormones and the like. Identification of such lead molecules waε impeded by the prior lack of a high-throughput εcreening εyεtem to discover active molecules, and the abεence of a structural data base upon which to design effective drug candidates. These barriers are now removed by cloning the parathyroid cell Ca 2+ receptor and functionally related receptors, and systematically examining the structural features of certain lead molecules that activate such cloned Ca 2+ receptor :εε and functionally related receptorε. Cloning of the Ca2+ receptor also enables development of transfected cell lines suitable for high-throughput screening of natural product or molecule libraries and synthetic molecules. This, together with structure-activity studies discuεεed below, provides the technology neceεsary to develop novel calcimimetics and calcilytics. Applicant enables such procedures in this application. A bovine parathyroid cell calcium receptor cDNA has been cloned and is deposited in the ATCC under accession number ATCC 75416. Uεing thiε clone, inorganic-ion receptors in other tiεsues and species homologε are easily obtained. For example, the human n paarraafthhvyrrnoiiHd n coe~l 1l Caa SUBSTITUTE SHEET ISA/EP receptor cDNA can be cloned by εcreening nucleic acid librarieε or by εcreening for functional expression in Xenopus oocytes, and the structural features of organic moleculeε neceεsary for activity on the Ca 2+ receptor can be determined through the testing of selected natural products or other molecule libraries and subεequent εtructure-activity studies. Thus, in a first aspect, the invention features a pharmaceutical compoεition including a molecule which either mimicε the activity of extracellular Ca 2+ by evoking an increaεe in [Ca 2+]• in a cell, or blockε an increaεe in [Ca 2+]. elicited by extracellular Ca2+. The molecule haε an EC- Q of less than or equal to 5 μM, and is not protamine. By "mimic" is meant that the molecule haε one or more of the specific actions of extracellular Ca 2+ on an extracellular Ca 2+ responεive cell. The term doeε not require that all of the biological functionε of extracellular Ca 2+ are mimicked, but rather that at leaεt one such function is mimicked. In addition it does not require that the molecule bind to the same site on the Ca 2+ receptor as does extracellular Ca2+ (see for example, the novel compound NPS 467 and its action in Example 20 below) . By "block" is meant that one such action of Ca 2+ is reduced or prevented by the molecule. The EC 5Q can be determined in aεεayε aε described below, where the activity mimicked is meaεured and the concentration of molecule which mimicε at half the maximum mimicking effect iε the EC 5Q . Conversely, the I 50 of a calcilytic is that amount which blocks half maximal activity. Preferably, - 11 εuch aεεayε measure to be specific to a below, or their equivalent. In preferred embodiments, bioassays described herein demonstrate that the increaεe in [Ca 2+] . in a cell is transient, having a duration of lesε than one minute, and the increaεe in [Ca 2+]. is rapid, occurring within thirty secondε; and the molecule also (a) evokes a suε tained increaεe (greater than thirty εeconds) in [Ca 2+]., (b) evokes an increase in inositol-l,4,5-triεphoεphate and/or diacylglycerol levels, e.g. , within less than 60 secondε, and (c) inhibitε dopamine- or iεoproterenol- stimulated cyclic AMP formation. In addition, the tran εient increaεe in [Ca 2+]. iε abolished by pretreatment of the cell for ten minutes with 10 mM sodium fluoride, or the transient increase is diminished by brief pretreatment (not more than ten minutes) of the cell with an activator of protein kinase C, e.g. , phorbol myristate acetate (PMA), mezerein or (-)indolactam V. In a parathyroid cell, those molecules which are active in all of the aεεayε deεcribed above are particularly uεeful in thiε invention εince they are εpecific in their actionε to a Ca 2+ receptor of such a cell. This is particularly true for the PMA pretreatment effect described above. In a more preferred embodiment, the cell is a parathyroid cell, and the molecule inhibits parathyroid hormone secretion from the cell. Other preferred embodiments include molecules that elicit an increase in [Ca2+]• as detected, for example, as an increase in Cl ~ current in a Xenopus oocyte injected with mRNA from a parathyroid cell, bone osteoclast, juxtaglomerular kidney cell, proximal tubule kidney cell, distal tubule kidney cell, cell of the thick ascending limb of Henle's loop and/or collecting duct, keratinocyte in the epidermis, parafollicular cell in the thyroid (C-cellε), intestinal cell, trophoblast in the placenta, platelet, vascular smooth muscle cell, cardiac atrial cell, gastrin and glucagon secreting cells, kidney mesangial cell and mammary cell. In other preferred embodimentε, the molecule evokeε the mobilization of mtracellular Ca 2+ to cauεe the increaεe in [Ca 2+].; the cell iε a C-cell or an oεteoclaεt and the molecule inhibits bone resorption in vivo; the cell is an osteoclaεt and the molecule inhibitε bone resorption in vitro; or the cell is a C- cell and the molecule stimulateε calcitonin εecretion in vitro or in vivo; and moεt preferably the molecule iε either a calcimimetic or calcilytic having an EC 5Q or IC 5Q at a Ca receptor of leεε than or equal to 5 μM, and even more preferably leεs than or equal to 1 μM, 100 nmolar, 10 nmolar, or 1 nmolar. Such lower EC D c U r .'s or ICDl) ' ε are advantageouε εince they allow lower concentration of moleculeε to be used in vivo or in vitro for therapy or diagnosiε. The diεcovery of moleculeε with such low EC ' s and IC ' s enables the design and εyntheεiε of εimilarly potent and efficaciouε moleculeε. By "calcimimetic" molecule iε meant any molecule which haε one or more activitieε of extracellular Ca 2+, and preferably mimicε the activity of Ca 2+ at a Ca_?+ receptor. For example, when used in reference to a parathyroid cell it is a molecule which, when tested on parathyroid cells in vitro, posεesseε one or more, and preferably all of the following characteristics as measured by techniques well known to those in the art: 1. The molecule causes a rapid (time to peak < 5 εec) and tranεient increase in [Ca 2+]. that is refractory to inhibition by 1 μM La 3+ or Gd3+. The increaεe in [Ca 2+]. perεiεts in the absence of extra cellular Ca 2+ but is aboli.shed by pretreatment with ionomycin (in the absence of extracellular Ca 2+); 2. The molecule potentiates increaseε in [Ca 2+]. elicited by εubmaximal concentrations of extracellular Ca 2+; 3. The increaεe in [Ca 2+]. elicited by 2 + . extracellular Ca is not inhibited by dihydropyπdmes; 4. The tranεient increase in [Ca 2+]. caused by the molecule is abolished by pretreatment for 10 min. with 10 mM sodium fluoride; 5. The transient increase in [Ca 2+]. caused by the molecule iε diminiεhed by pretreatment with an activator of protein kinaεe C (PKC), εuch as phorbol myristate acetate (PMA), mezerein or (-)-indolactam V. The overall effect of the protein kinaεe C activator iε to shift the concentration-response curve of the molecule to the right without affecting the maximal responεe; 6. The molecule cauεeε a rapid (< 30 εec.) increaεe in the formation of inoεitol-1,4,5- triεphosphate and or diacylglycerol; 7. The molecule inhibits dopamine- or isopro terenol-stimulated cyclic AMP formation; 8. The molecule inhibits PTH secretion; 9. Pretreatment with pertussis toxin (100 ng/ml for > 4 hrs.) blocks the inhibitory effect of the molecule on cyclic AMP formation but does not effect increases in [ Ca 2+ ] . , mositol-1 , 4 , 5-tπsphoεphate , or diacylglycerol, nor decreaεeε in PTH εecretion; 10. The molecule elicitε increaεeε in [Ca 2+]. aε detected, for example, as an increase in Cl ~ current in Xenopus oocytes injected with poly(A) - enriched mRNA from bovine or human parathyroid cells but is without effect in Xenopus oocytes injected with water or rat brain or liver mRNA; and 11. Similarly, using a cloned receptor from parathyroid cells, the molecule will elicit a responεe in Xenopuε oocyteε injected with the specific cDNA, mRNA or synthetic sense RNA (cRNA) encoding the receptor. By "calcilytic" molecule is meant any molecule which blocks one or more of the activities of extracellular Ca 2+ on an extracellular Ca2+-sensing cell, preferably by acting as an antagonist at the Ca 2+ receptor. For example, when used in reference to a parathyroid cell, it is a molecule which, when tested on parathyroid cells in vitro, posεeεεeε one or more, and preferably all of the following characteristics as measured by techniques well known to those in the art: 1. The molecule blocks, either partially or completely, the ability of increaεed concentrationε of extracellular Ca 2+ to: a) increaεe [Ca 2+]., b) mobilize mtracellular Ca2+, c) increase the formation of inositol- 1,4,5-triεphoεphate, d) decrease dopamine- or isoproterenol- εtimulated cyclic AMP formation, and e) inhibit PTH εecretion; 2. At low [Ca 2+] , i.e., 0.5 mM, the molecule by itself does not change [Ca 2+]. 3. The molecule blockε increaεeε in Cl current in Xenopuε oocytes injected with poly(A) - mRNA from bovine or human parathyroid cells elicited by extracellular Ca 2+ or calcimimetic compounds but not in Xenopus oocytes injected with water or rat brain or liver mRNA; 4. Similarly, using a cloned receptor from parathyroid cells, the molecule will block a reεponεe in Xenopus oocyteε injected with the εpecific cDNA, mRNA or cRNA encoding the Ca 2+ receptor, elicited by extracellular Ca 2+ or a calcimimetic compound. Parallel definitionε of uεeful calcimimeticε and calcilyticε at Ca 2+ receptorε on other cell typeε are evident from the exampleε provided below. The Ca 2+ receptor lε able to detect and reεpond to certain inorganic polycationε and polycationic organic moleculeε. For example, the parathyroid cell iε unable to diεtinguiεh increaεeε in extracellular Ca 2+ concentration from the addition of theεe organic polycationε, preεumably becauεe theεe organic moleculeε act juεt like extracellular Ca 2+ at the Ca2+ receptor. The calcimimetic moleculeε of this invention are particularly good agonists of the - 16 - Ca 2+ receptor and may be used as drugs that alter selected cellular functions, e.g. , secretion of PTH from parathyroid cells. Unlike Ca most of these molecules act only at one or more, but not all Ca 2+ receptorε, and thus provide an ability to specifically target one Ca 2+ receptor. Theεe molecules also provide lead structureε for the development of further novel therapeuticε effective in the treatment of variouε diseaseε where [Ca 2+]. and [Ca 2+] play a role, such as hyperparathyroidism, oεteoporoεiε, Paget' ε disease, hypertension, renal diεeaεe, εkin diseaεe, cardiovaεcular diεeaεe, blood clotting diεorderε, gaεtorintestinal diseaεeε, endocrine diseases, abnormalities in water metabolism and cancer. The calcimimetics and calcilytics can be formu lated as pharmaceutical compositions which are useful for regulat g the level of extracellular free Ca 2+ in a patient and for mimicking the effect of extracellular Ca 2+ on a cell selected from the group described above, by administering to the patient such a pharmaceutical composition. Prior to this invention, applicant was unaware of any such molecules acting on the Ca 2+ receptor useful in treatment of diεeaεeε cauεed by irregularity in operation or regulation of a Ca 2+ receptor or diseaseε m an animal having normal Ca 2+ receptorε but which can be treated by activating or deactivating εuch Ca 2+ receptors. In yet another preferred embodiment, the molecule haε an EC 5Q less than or equal to 5 μM at one or more but not all cells chosen from the group consiεting of parathyroid cellε, bone oεteoclastε, juxtaglomerular kidney cells, proximal tubule kidney cells, distal tubule kidney cell, cell of the thick ascending limb of Henle's loop and/or collecting duct, keratinocyte in the epidermis, parafollicular cell in the thyroid (C-cells), intestinal cell, trophoblast in the placenta, platelet, vascular smooth muscle cell, cardiac atrial cell, gastrin and glucagon εecreting cells, kidney mesangial cell and mammary cell. It is the specificity of action of such molecules that iε particularly advantageous in this invention since it allows specific in vivo and in vitro therapy and diagnosis and discovery of additional calcimimetic or calcilytic molecules. In specific preferred embodimentε, the molecule iε positively charged at physiological pH, and is selected from the group consisting of branched or cyclic polyamineε, positively charged polyamino acids, and arylalkylamines, e.g. , the branched polyamine has the formula H 2 N-(CH 2 ) .-(NR i -(CH 2 ) .) k -NH 2 where k is an integer from 1 to 10, each j is the same or different and iε an integer from 2 to 20, and each R. is the εame or different and iε εelected from the group conεiεting of hydrogen and -(CH ) .-NH 2 , where j iε aε defined above, and at least one R. is not hydrogen. In an alternative embodiment, the molecule has the formula where each X independently is selected from the group consisting of H, CH 3 , CH 3 0, CH 3 CH 2 0, Br, Cl, F, CF 3 , CHF 2 , CH 2 F, CF 3 0, CH 3 S, OH, CH 2 OH, CONH 2 , CN, N0 2 , and CH 3 CH 2 ; Ar is a hydrophobic entity; each R independently is selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, indenyl, indanyl, dihydroindolyl, thiodihydroindolyl, 2-, 3-, or 4- piperid(in)yl; Y is selected from the group conεiεting of CH, nitrogen and an unεaturated carbon; Z iε εelected from the group conεiεting of oxygen, nitrogen, sulfur. where each n is independently between l and 4 inclusive, and each m is independently between 0 and 5 inclusive. Most preferably the molecule iε either a calcimimetic or calcilytic In preferred embodiments, the hydrophobic entity iε selected from the group consisting of phenyl, 2-, 3-, or 4-pyridyl, 1- or 2-naphthyl, 1- or 2- quinolinyl, 2- or 3-indolyl, benzyl, and phenoxy; the molecule iε an R-phenylpropyl-α-phenethylamine derivative, and the molecule haε the formula: with each X preferably being independently selected from the group consisting of Cl, F, CF3, CH3, and CH 3 O. According to a preferred aspect of the present invention, novel phenylpropyl-α-phenethylamine analogs and derivatives are provided having the formula: wherein alk iε εtraight or branched chain alkylene of from 1 to 6 carbon atomε; RI iε lower alkyl of from 1 to 3 carbon atomε or lower haloalky 1 of from 1 to 3 carbon atomε εubstituted with from 1 to 7 halog en atomε; R and R are independently εelected carbocyclic a ryl or cycloalkyl groupε, either monocyclic or bicyclic, having 5- or 6-membered ringε optionally εubεtituted with 1 to 5 substituentε independently εelected from lower alkyl of 1 to 3 carbon atomε, lower haloalkyl of 1 to 3 carbon atomε εubstituted with 1 to 7 halogen atoms, lower alkoxy of 1 to 3 carbon atomε, halogen, nitro, amino, alkylamino, amido, lower alkylamido of 1 to 3 carbon atomε, cyano, hydroxy, acyl of 2 to 4 carbon atomε lower hydroxyalkyl of 1 to 3 carbon atomε or lower thioalkyl of 1 to 3 carbon atomε. Suitable carbocyclic aryl groupε are groupε having one or two ringε, at leaεt one of which having aromatic character and include carbocyclic aryl groupε εuch aε phenyl and bicyclic carbocyclic aryl groups εuch aε naphthyl. As is apparent from the above formula, the compounds encompasεed therein may exiεt aε racemic mixtureε and as individual stereoisomerε. Eεpecially preferred are R-phenylpropyl α-phenethylamine derivativeε which exhibit enhanced activity in lowering εerum ionized calcium. Preferred compoundε include thoεe where alk iε n-propylene. Alεo preferred are compoundε where R is methyl. Alεo preferred are those compounds where R 2 and R 3 are optionally substituted phenyl. Especially preferred compounds include those where R„ is monosubεtituted phenyl, more preferably meta-substituted. Especially preferred R 3 groups include unsubεtituted or monoεubstituted phenyl, especially ortho-εubεtituted. Preferred εubεtitutentε for R 2 include halogen, haloalkyl, preferably trihalomethyl, and alkoxy, preferably methoxy. Preferred substituents for R 3 include halogen, preferably chlorine. In a second related aspect, the invention fea tures a method for treating a patient having a disease or condition characterized by an abnormal [Ca 2+] or [Ca2+]• in one or more cells or in the blood or plaεma or extracellular fluidε. The method includeε the εtep of administering to the patient a therapeutically effective amount of a molecule which either mimics the activity of extracellular Ca 2+ by evoking an increaεe in [Ca 2+]. in a cell or blockε an increaεe in [Ca 2+]. elicited by extracellular Ca2+ By "abnormal" iε meant that the patient, compared to the general population, haε a different Ca 2+ metaboliεm that iε affected by one or more proteinε (e.g. , hormoneε) in the blood or extracellular body fluidε, or other moleculeε which affect the level of extracellular and/or mtracellular Ca 2+. Thuε, the diseaεeε include hyperparathyroidiεm, oεteoporosis and other bone and mineral-related disorderε, and the like (aε deεcribed, e.g. , in standard medical text books, such as "Harrison's Principles of Internal Medicine"). Such diseaεes are treated in this invention by molecules which mimic or block one or more of the effects of Ca 2+ and thereby directly or indirectly affect the levels of the proteinε or other moleculeε in the body of the patient. By "therapeutically effective amount" iε meant an amount that relieves to some extent one or more symptoms of the diseaεe or condition in the patient. Additionally, by "therapeutically effective amount" is meant an amount that returns to normal, either partially or completely, physiological or biochemical parameters aεεociated with or cauεative of the diεeaεe or condition. Generally, it iε an amount between about 1 nmole and 1 μmole of the molecule, dependent on itε EC 50 and on the age, εize, and diεeaεe aεεociated with the patient. In preferred embodimentε, the molecule haε an EC 50 of leεε than or equal to 5 μM, and iε not protamine; and moεt preferably mteractε at a Ca 2+ receptor aε a calcimimetic or calcilytic. Moεt preferably the molecule iε choεen from one of thoεe described above. In other preferred embodiments, the patient has a diseaεe characterized by an abnormal level of one or more componentε the level of which iε regulated or affected by activity of one or more Ca 2+ receptorε, and the molecule lε active on a Ca 2+ receptor of a cell εelected from the group conεiεting of parathyroid cellε, bone oεteoclaεtε, juxtaglomerular kidney cellε, proximal tubule kidney cellε, diεtal tubule kidney cell, cell of the thick aεcending limb of Henle'ε loop and/or collecting duct, keratinocyte in the epidermiε, parafollicular cell in the thyroid (C-cellε), intestinal cell, trophoblast in the placenta, platelet, vaεcular εmooth muεcle cell, cardiac atrial cell, gaεtrin and glucagon secreting cells, kidney mesangial cell and mammary cell. In still other preferred embodiments, the mole cule reduces the level of parathyroid hormone in the serum of the patient, e.g. , to that level present in a normal individual, or to a degree sufficient to cause a decrease in plasma Ca 2+; and the molecule is provided in an amount sufficient to have a therapeutically relevant effect on the patient. In a third aspect, the invention features a method for diagnoεis of a diseaεe or condition in a patient by identifying the number and/or location (and/or functional mtegrity) of one or more Ca 2+ receptorε within the patient and comparing that number and/or location (and/or functional integrity) with that obεerved in normal patientε as an indication of the presence of the diseaεe or condition. In preferred embodi entε, the method iε an lmmunoaεεay m which an antibody to a Ca 2+ receptor lε uεed to identify the number and/or location and/or functional mtegrity of the Ca 2+ receptorε, or the aεεay involves providing a labelled calcimimetic or calcilytic molecule which binds to a Ca 2+ receptor; and the diεeaεe diagnoεed iε a cancer, e.g., an ectopic tumor of the parathyroid, or a condition characterized by an above normal level in the number of oεteoclaεtε in bone or an increaεed level of activity of oεteoclaεtε in bone. In a fourth aεpect, the invention featureε a method for identifying a molecule uεeful aε a therapeutic molecule. The method includeε screening a potentially useful molecule for either an ability to mimic the activity of extracellular Ca 2+ in a cell, or to block an increase in [Ca2+]. elicited by extracellular Ca 2+, and determining wh 1 ether the molecule haε an EC 5Q or IC 5Q of leεs than or equal to 5 μM. In other aspects, the invention features a recombinant Ca 2+ receptor, a cell including a recombinant Ca 2+ receptor, purified nuclei.c aci.d encoding a Ca2+ receptor, the biological activity and use of the molecule NPS 019, the novel compounds or compositionε of matter of NPS 459, NPS 467, and NPS 568 (see Fig. 36) and a method for identifying a useful calcimimetic or calcilytic molecule by identifying a molecule which mimics or blocks one or more activitieε of Ca 2+ at a fi.rεt Ca 2+ receptor but not at a second Ca 2+ receptor, e.g. , by use of a recombi.nant Ca2+ receptor. In another aεpect, a cell including a recombinant Ca 2+ receptor(ε) from kidney lε employed aε a teεt system to screen antibiotics (e.g. aminoglycoside antibioticε) for activity at calcium receptorε which produceε renal toxicity in humanε. By "recombinant" lε meant to include any Ca 2+ receptor produced by recombinant DNA techniqueε εuch that it ιε distinct from the naturally occurring Ca 2+ receptor either in its location, purity or structure. Generally, such a receptor will be present in a cell in an amount different from those normally observed in nature. By "purified" is meant that the antibody or nucleic acid iε distinct from naturally occurring antibody or nucleic acid, being separated from antibody or nucleic acid with which it naturally occurs, e.g. , in a vector εyεtem, εuch that it can be used to express recombinant Ca 2+ receptor. Preferably, the antibody or nucleic acid is provided aε a ho ogeneouε preparation by εtandard techniqueε. Such cloned receptorε can be expreεεed in a desired cell, and isolated and crystallized to allow structure determination. Such a structure will allow design of useful 2+ moleculeε of this invention which can bind to the Ca receptor. In addition, equivalent such receptors can be cloned using a firεt clone aε a probe for clones in other cell, cDNA or genomic libraries. Antibodies to the cloned receptor can be isolated and uεed aε therapeuticε in thiε invention, or aε diagnoεtic toolε for determining Ca 2+ receptor numberε and/or locations and/or functional integrity to diagnose Ca 2+-related diseaεes or conditions. Such antibodies can also be uεed in vivo by intravenouε adminiεtration aε calcimimeticε or calcilyticε. Thuε, in general, the invention featureε calcimimetic or calcilytic moleculeε able to act as either εelective agoniεts or antagonists respectively at a Ca 2+ receptor of one or more but not all cells chosen from the group consiεting of parathyroid cellε, bone oεteoclaεtε, juxtaglomerular kidney cellε, proximal tubule kidney cellε, diεtal tubule kidney cell, cell of the thick aεcending limb of Henle'ε loop and/or collecting duct, keratinocyte in the epidermiε, parafollicular cell in the thyroid (C-cellε), intestinal cell, trophoblast in the placenta, platelet, vascular smooth muεcle cell, cardiac atrial cell, gaεtrin and glucagon εecreting cellε, kidney meεangial cell and mammary cell. Such a compoεition may include any pharmaceutically acceptable carrier known to thoεe in the art to provide a pharmaceutical compoεition. The invention alεo featureε modulation of the number of Ca 2+ receptorε in a patient by εtandard techniqueε, e.g. , antiεenεe and related technologieε (e.g. , ribozy eε), aε a therapeutic for a diεease state. This invention provides methods for identifying moleculeε which affect the acti .vi.ty of a Ca2+ receptor using asεayε, aε defined below, to detect calcimimetics and/or calcilyticε. Further, moleculeε found to be effective to reduce or enhance expreεεion of Ca 2+ receptor at a tranεcriptional or tranεlational level by use of the asεays or antibodies or other techniques described below can be defined for therapeutic useε. The foregoing εummary haε been largely in connection with the preferred embodiment which relateε generally to calcium receptorε. In a further aεpect, the invention relateε to a novel εuperfamily of polypeptide receptor/εenεor moleculeε. The cDNA clone, BoPCaR 1, disclosed herein and duly deposited, represents the first such clone described to encode a receptor/senεor which iε a member of thiε εuperfamily. For purpoεeε of the preεent invention, receptor/εenεorε belonging to thiε εuperfamily are called inorganic-ion receptorε. The novel εuperfamily of inorganic ion receptorε includeε a variety of εuch moleculeε which are related to each other by εimilarity of amino acid εequence, by εtructure and/or by function. In total, theεe attributeε alεo diεtinguiεh memberε of thiε εuperfamily of receptorε from all receptorε/εenεorε currently known in the art. Memberε of thiε εuperfamily of receptorε are primarily diεtinguished functionally by their surprising ability to detect and respond to changes in the levels of inorganic cations such as calcium, magneεium, potaεεium, εodium, or hydrogen ionε and the like, and upon sensing such ions, to evoke changes in cellular functions. Such changes may involve changes in second mesεenger levels as occur for known G-protein coupled receptors, or changes in ionic tranεmembrane ion flux or the like. Other memberε of thiε εuperfamily alεo exiεt which εense inorganic anions εuch as phosphate or chloride ions. All such receptors are within the εcope of the current invention aε deεcribed herein. Additionally, all iεolated naturally occurring or εynthetic ligandε for receptorε/εensors belonging to the superfamily of inorganic-ion receptorε are within the εcope of the invention. In an additional aεpect, the invention featureε the therapeutic uεe of any εuch natural or εynthetic ligands for inorganic-ion receptorε. It is a further aspect of the present invention that receptors belonging to the superfamily of inorganic-ion receptors may be activated by stimuli other than ligand binding. For example, some members of this superfamily of receptors are activated by physical forces such as stretch forces acting on membraneε of cellε expreεεing εuch receptorε. All εuch receptorε are within the εcope of the preεent invention. The inorganic-ion receptorε can be uεed in the manner aε deεcribed above in connection with the preferred receptor. Recombinant receptorε expreεεed in a variety of tiεεue typeε including human tiεεue typeε can be uεed to εcreen (including high through-put εcreenε) for drug diεcovery in methodε known to thoεe skilled in the art. Ionmimetics and ionlyticε can be readily identified. The procedureε can be adapted for the individual function of the receptor. For example, calcium activated chloride current may be employed with an inorganic-ion receptor which formε a calcium channel or which nutrilizeε mtracellular calcium. Ligand-gated ion channels are known in the art. Inorganic-ion receptorε that couple to εecond meεεenger εyεtems permit aεsays as deεcribed above, including measurement of cyclic AMP and inositol phosphateε. Cellε that have recombinant receptorε coupled to readily detectable agentε alεo may be uεed εuch aε G-protein coupling of receptorε to pigment diεperεion in melanophoreε aε deεcribed in the literature. Thus, the invention fully enables methods for discovering agents that are inorganic-ion receptor mimetics or lyticε, as well as such mimetics and lyticε themεelveε, including thoεe preferably εelected from the mimeticε and lyticε deεcribed in detail above. Likewiεe, the invention embraces diagnosis and treatment of inorganic-ion receptor related diseaεeε or conditionε aε deεcribed above in connection with the preferred embodiment. For example, diεeaεes asεociated with elevated levelε of an inorganic-ion receptor can be diagnoεed baεed upon aεεays for such elevated levelε. Therapeutic moleculeε can be identified by εcreening for agentε that mimic the activity of the relevant native ion or that modify the effect or potency of the relevant native ion. Tiεεue εpecific expreεεion aε well as levels of expresεion can be evaluated and the like. Thuε, in thiε aεpect of the invention, a novel εuperfamily of iεolated inorganic-ion receptorε iε provided and unique fragmentε thereof alεo are provided. Preferably, the iεolated receptorε are human receptorε, and most preferably the iεolated receptor iε a calcium receptor expreεεed in tiεεueε or cellε εelected from the group conεiεting of: parathyroid, vaεcular, kidney, epidermiε, thyroid, osteoclast, inteεtine, mammary, trophoblaεt. platelet, gaεtrin secreting, glucagon secreting, cardiac, and brain, and unique fragments thereof. The invention further features polypeptide fragments of the foregoing inorganic-ion receptors which have desirable activity. For example, the fragment may include just a binding site, or a site which binds to mimics, agonistε or antagonistε. Other uεeful fragmentε include those that have only the external portion, membrane-spanning portions, or mtracellular portion of the receptor. In addition, these fragmentε are uεeful for forming chimeric receptorε with fragmentε of other receptorε, aε deεcribed in greater detail below. The invention alεo featureε muteinε or analogueε and other derivativeε of the iεolated receptorε. Thuε, the invention embraceε not only naturally occurring proteinε, but derivativeε thereof. The invention alεo featureε nucleotide εequenceε encoding the foregoing inorganic-ion receptorε and fragmentε and derivatives thereof. Such nucleotide sequenceε may be obtained through a variety of procedureε, and the diεclosure of the present invention allows one of ordinary skill in the art to obtain cDNA or genomic clones encoding such receptors. For example, hybridization probeε may be made baεed upon the nucleotide εequence of BoPCaR 1. When genomic librarieε for cDNA librarieε from any tiεεue are εcreened at low εtringency with εuch probeε, hybridizing cloneε are obtained which encode other memberε of the εuperfamily. Additionally, antibodieε can readily be prepared which bind to cloned or isolated inorganic-ion receptors. Such antibodies may alεo be uεed to iεolate other receptorε of the invention by expreεεion-cloning techniqueε known to thoεe of ordinary εkill in the art. Targeted gene walking alεo may be employed to identify and clone members of the superfamily of inorganic-ion receptorε. In addition, the clones may be obtained through expreεεion cloning procedures as described above. Theεe procedureε can be adapted for the individual function of the inorganic-ion receptor of intereεt. For example, calcium activated chloride currentε may alεo be employed for cloning of an inorganic-ion receptor which formε a calcium channel or which mobilizeε mtracellular calcium. Ligand-gated ion channelε, aε diεcuεεed above, are known in the art. For example, a εerotonin gated ion channel haε been cloned in thiε manner. However, the receptorε of the preεent invention are diεtinct from other known ligand gated ion channelε in their amino acid εequenceε and in that they sense inorganic ionε εuch as calcium, magnesium, hydrogen ions, phosphate ions, and the like. It will alεo be appreciated by thoεe εkilled in the art that each cloned receptor obtained in this manner provides new such DNA or antibody probes which themselveε are uεed to identify still additional clones encoding inorganic-ion receptors. Furthermore, it will be appreciated that having obtained the εequence of more than one εuch receptor aε outlined above, information iε available pertaining to localized εequence conεervation which iε useful for obtaining still additional cloneε encoding other members of the εuperfamily. Such conεerved εequenceε alεo may be derived from an analyεiε of the overall εtructure of BoPCaR 1, aε it conventionally includeε an extracellular domain, tranεmembrane domain and mtracellular domain. Thuε, iεolated nucleic acidε encoding inorganic-ion receptorε and unique fragmentε thereof are provided. The preferred receptor iε a calcium receptor that iε expressed in - 30 - the tiεsues or cellε εelected from the group deεcribed above. Most preferably, the nucleic acid encodes a human inorganic-ion receptor or a unique fragment thereof. The invention further provides isolation of the endogenous regulatory elements controlling the expresεion of the foregoing inorganic-ion receptors, and agents that are capable of agonizing or antagonizing the activity of theεe regulatory elementε alεo may be identified. The invention further provideε recombinant cells expressing the nucleic acids of the invention. In such cells, the nucleic acid may be under the control of its genomic regulatory elementε, or may be under the control of exogenouε regulatory elementε including an exogenouε promoter. By "exogenouε" it iε meant a promoter that iε not normally coupled m vivo tranεcriptionally to the coding εequence for the inorganic-ion receptor. Purified antibodieε to the foregoing inorganic-ion receptorε are provided aε well aε antibodieε to alloεteric εiteε of εuch receptorε and idiotypeε of such receptors. Inorganic-ion receptor binding agents coupled to a toxin also are provided. Such agents may be antibodies and, aε εuch, are immunotoxinε. Such immunotoxinε may be uεed for example in killing a cell expreεεing an inorganic-ion receptor in vitro or m vivo. In addition, the invention provideε tranεgenic, nonhuman mammalε containing a tranεgene encoding an inorganic-ion receptor or a unique fragment thereof. Such tranεgenes may be useful in affecting or altering the expression of an inorganic-ion receptor or in inactivating the expresεion of an inorganic-ion receptor through, for example, homologouε recombination. Other tranεgeneε may be provided in εuch mammalε, including those encoding antisenεe or a protein that iε capable of altering the expreεεion of a native inorganic-ion receptor gene. Such alteration may be up-regulation, down-regulation or complete inactivation. Thuε, methodε are provided involving contacting a cell with an agent that bindε to a cellular component for the purpose of affecting the expression of an inorganic-ion receptor. Such agents may bind to promoters, other regulatory agents acting on promoterε, agentε capable of binding to the receptor and nucleic acidε encoding the receptor or a unique fragment thereof. Contact may be by extracellular admmiεtration, by providing a tranεgene encoding the agent or by any other εuitable method depending upon the uεe to which the particular method iε directed. Other featureε and advantageε of the invention will be apparent from the following deεcription of the preferred embodimentε thereof, and from the claimε. Deεcription of the Preferred Embodimentε The drawingε will firεt briefly be deεcribed. Drawingε Fig. 1 depictε repreεentative moleculeε uεeful in the invention. Fig. 2 iε a graphical repreεentation εhowing increaεeε in [Ca 2+]. induced by extracellular Ca2+ in quin-2- or fura-2-loaded bovine parathyroid cellε. The initial [Ca 2+] waε 0.5 mM (uεing CaCl 2 ) and, at each of the arrowε, waε increaεed in 0.5 mM incrementε. Fig. 3 iε a graphical repreεentation showing mobilization of [Ca 2+]. in bovine parathyroid cellε. The initial [Ca2+] was 0.5 mM and was decreased to < 1 μM by 2+ the addition of EGTA as indicated. (a) Extracellular Mg (8 mM, final) elicits an increase in [Ca 2+]. in the absence of extracellular Ca 2+. (b) Pretreatment with ionomycin (1 μM) blocks the responεe to Mg 2+. (c) Pretreatment with 5 μM molecule 1799 (a mitochondrial uncoupler) lε without effect on the reεponεe to Mg 2+ Fig. 4 iε a graphical repreεentation showing preferential inhibitory effects of a low concentration of Gd 3+ on steady-εtate increaεeε in [Ca2+]. and that a high concentration of Gd 3+ elicits a transi.ent i.ncreaεe in [Ca]. in bovine parathyroid cellε. Top panel: Control. Ini .tial concentration of extracellular Ca2+ waε 0.5 mM and was increased by 0.5 mM at each of the arrowheads. Middle panel : Gd 3+ (5 μM) blocks steady-εtate but not tranεient mcreaεeε in [Ca 2+]. elicited by extracellular Ca2+ Lower panel: Gd 3+ (50 μM) elicitε a tranεient increaεe in [Ca 2+]. and aboliεheε both tranεient and sustained responseε to extracellular Ca 2+. In the middle and lower panelε, juεt enough EGTA waε added to chelate preferentially Gd 3+: the block of Ca2+ influx iε removed and [Ca2+] . rises promptly. Fig. 5 is a graphical representation showing that the effects of PMA on [Ca + ] ^ , IP 3 formation, and PTH secretion are overcome by increasing concentrations of extracellular Ca 2+ m. bovine parathyroid cells. For each variable, there is a shift to the right in the concentration-reεponεe curve for extracellular Ca 2+. Note alεo that the concentration- reεponεe curveε vary εigmoidally aε [Ca 2+] increaεeε linearly. Fig. 6 is a graphical representation showing that increaεeε in [Ca 2+]. elicited by εpermine are progressively depressed by increasing [Ca 2+] in bovine parathyroid cells. Spermine (200 μM) was added at the time shown by arrowheads. In thiε and all subsequent figures, the numberε accompanying the traceε are [Ca 2+]• in nM. Fig. 7 iε a graphical repreεentation εhowing that εpermine mobilizes mtracellular Ca 2+ in bovine parathyroid cells. EGTA waε added to reduce [Ca 2+] to <1 aM before the addition of spermine (200 μM) as indicated (left trace). Pretreatment with ionomycin (1 μM) blocks the response to spermine (right trace). Figs. 8A and B are graphical representations showing that εpermine increaεeε [Ca ]. and inhibitε PTH secretion in bovine parathyroid cells similarly to extracellular Ca 2+. The data points for the spermine dose-concentration responεe curveε are the meanε of two experiments. Fig. 9 is a graphical representation showing the contrasting effects of PMA on responεeε to extracellular Ca 2+ and on reεponεeε to ATPγS i.n bovi.ne parathyroi.d cellε. Left panel: The concentration- reεponεe curve for extracellular Ca 2+-induced inhibition of cyclic AMP formation iε εhifted to the right by PMA (100 nM) . Middle panel: PMA doeε not affect the ability of ATPγS to increaεeε [Ca 2+].. Note alεo that the concentration-reεponεe curve to ATPγS εhows classical sigmoidal behavior as a function of the log concentration, in contrast to extracellular divalent cations. Fig. 10 iε a graphical repreεentation showing mobilization of mtracellular Ca 2+ in human parathyroid cells evoked by extracellular Mg2+. Cells were obtained from an adenoma and bathed in buffer containing 0.5 mM extracellular Ca 2+. (a) Transi.ent and sustai.ned i.ncreases in [Ca 2+ ]. elicited by extracellular Mg 2+ (10 mM, final) showε that εustained increaseε are not affected by nimodipine (1 μM) but are depreεεed by La 3+ (1 μM) and return promptly when La 3+ iε εelectively chelated by a low concentration of EGTA. (b) La 3+ (1 μM) blockε the εuεtained but not the tranεient increaεe in [Ca 2+]. elicited by extracellular Mg 2+. (c) Cytosolic Ca2+ transientε elicited by extracellular Mg 2+ perεiεt in the abεence of extracellular Ca 2+ Fig. 11 iε a graphical repreεentation εhowing mobilization of mtracellular Ca 2+ evoked by neomycin or protamine in bovine parathyroid cellε. In all traceε, the initial [Ca 2+] and [Mg2+] waε 0.5 and 1 mM, reεpectively. In trace (a) and (b) , the Ca 2+ and Mg2+ concentrationε were increaεed to 2 and 8 mM, from 0.5 and 1 mM reεpectively. In the other traceε, (c) through (i), neomycin B (30 μM) or protamine (1 μg/ml) were added aε indicated. La 3+ (1 μM) EGTA (1 mM) , or ionomycin (100 nM) were added aε indicated. Each trace iε representative of the pattern seen in 5 or more trialε uεing at leaεt 3 different cell preparations. Bar = 1 min. Fig. 12 is a graphical repreεentation εhowing that neomycin B blockε tranεient but does not block steady-εtate increaεeε in [Ca 2+]. elicited by extracellular Ca2+ in bovine parathyroid cellε. Left control: [Ca 2+] waε initially 0.5 mM and waε increaεed in 0.5 mM incrementε at each of the open arrowheadε before the addition of neomycin B (30 μM) . Right: Neomycin B (30 μM) was added before [Ca ] . Bar = 1 min. Fig. 13 is a graphical representation showing that neomycin B or protamine inhibit PTH secretion at concentrationε which evoked increaεeε in [Ca 2+]■ in bovine parathyroid cells. Cellε were incubated with the indicated concentrationε of organic polycation for 30 min. in the preεence of 0.5 mM extracellular Ca 2+. Open εymbols: control responses for PTH secretion in the presence of 0.5 (circles) or 2 mM (diamonds) extracellular Ca 2+. Values for [Ca 2+], are diamond symbols. Bovine cells were used in the experimentε with protamine and human (adenoma) parathyroid cellε were uεed in the experimentε with neomycin B. Each point iε the mean + SEM of 3 experimentε. Fig. 14 iε a graphical repreεentation εhowing the preferential inhibitory effects of PMA on cytosolic Ca 2+ tranεients elicited by εpermine in bovine parathyroid cellε. Initial [Ca 2+] waε 0.5 mM; εpermine (200 μM) or ATP (50 μM) were added aε indicated. Bar = 1 min. Fig. 15 iε a graphical repreεentation εhowing that PMA εhifts to the right the concentration-responεe curves for extracellular Ca 2+- and neomycin B-mduced increaseε m [Ca 2+]. in bovine parathyroid cellε. Cellε were pretrea 1 ted with PMA for 1 min. before increaεing [Ca2+] or before adding neomycin B aε indicated. Each point iε the mean + SEM of 3 to 5 experimentε. Fig. 16 iε a graphical representation showing that PMA shiftε to the right the concentration-reεponεe curveε for extracellular Ca 2+ - and spermme-mduced inhibition of PTH secretion in bovine parathyroid cells. Cells were incubated 2+ with the indicated [Ca ] and spermine for 30 min. the presence (closed circles) or absence (open circles) of 100 nM PMA. Each point is the mean + SEM of 3 experiments. Fig. 17 is a graphical representation showing that protamine increaseε the formation of inositol phosphateε in bovine parathyroid cellε. Parathyroid cellε were incubated overnight in culture media containing 4 μCi/ml H-myo-inoεitol, waεhed, and incubated with the indicated concentration of protamine at 37°. After 30 εec. the reaction waε terminated by the addition of CHC1 3 : eOH:HCl and IP, (circles) and IP, (triangles) εeparated by anion exchange chromatography. Each point is the mean of 2 experiments, each performed in triplicate. Fig. 18 is a graphical representation showing that PMA depreεεeε the formation of IP. evoked by extracellular Ca 2+ or spermine in bovine parathyroid cells. 3 H-myo-inositol- labeled cells were exposed to the indicated [Ca 2+] or spermine for 30 sec. before terminating the reaction and determining IP., by anion exchange chromatography. Hatched columns: Cellε were pretreated with PMA (100 nM) for 5 min. before increaεing [Ca 2+] or adding εpermine. Each value iε the mean of 2 experimentε, each performed in triplicate. Fig. 19 iε a graphical repreεentation εhowing tranεient and sustained increaseε in [Ca 2+]. elicited by neomycin B in human (adenoma) parathyroid ce 1 lls. [Ca2+] waε 2+ 0.5 mM. (a) The εuεtained increaεe in [Ca ]. elicited by neomycin B (10 μM) waε depreεsed by La 3+. (b")*" The 2+ tranεient increaεe in [Ca ]. evoked by neomycin B waε unaffected by La 3+. (c) Transient increaεeε in [Ca2+]. persisted in the absence of extracellular Ca2+ Fig. 20 is a graphical representation εhowing that neomycin B evokeε oεcillating increases the Cl current in Xenopuε oocyteε expressing the Ca 2+ receptor. Upper trace from an oocyte three days after injection with human (hyperplastic) parathyroid cell poly(A) -mRNA. Lower trace from an oocyte injected with water. Neomycin B failed to elicit a reεponεe in five water-injected oocyteε and carbachol elicited a reεponse in one, which is εhown. In both traces, the holding potential was -76 mV. Fig. 21 is a graphical representation εhowing that neomycin B failε to affect baεal or evoked increaεeε in C-cells. Control, left trace: Fura-2- loaded rMTC 6-23 cells were initially bathed in buffer containing 1 mM Ca 2+ before 2 - increaεing [Ca ] to 3 mM. Right trace: pretreatment with 5 mM neomycin B. Fig. 22 iε a graphical repreεentation εhowing that extracellular Ca 2+ evokeε increaεeε in [Ca2+]• in rat oεteoclaεtε. Microfluorimetric recording in a εingle rat osteoclast loaded with indo-1 and superfuεed for the indicated timeε (barε) with buffer containing the indicated [Ca 2+] . Normal buffer, εuperfused between the bars, contained 1 mM Ca 2+ . Fig. 23 is a graphical representation showing that spermine or neomycin B fail to evoke increaseε in [Ca 2+] . in rat oεteoclaεtε. An indo-1-loaded osteoclast was superfuεed with the indicated concentration of εpermine or neomycin B (open barε) alone or together with 20 mM Ca 2+ (εolid barε) . Fig. 24 is a graphical representation showing the differential effects of argiotoxin (shown as argiopine in the figure, structures also shown in Fig. 1) 659 and argiotoxin 636 on [Ca 2+]. in bovine parathyroid cells. The initial [Ca 2+] was 0.5 mM and was increased to 1.5 mM where indicated (right trace)N Where indicated, argiotoxin 659 (300 μM) or argiotoxin 636 (400 μM) was added. Fig. 25 is a graphical representation showing that extracellular Mg 2+ or Gd3+ evoke oscillatory increaseε in Cl current in Xenopuε oocytes injected with bovine parathyroid cell poly(A) -mRNA. In trace (a), the concentration of extracellular Ca 2+ was < 1 μM and m trace (b), 0.7 mM. Trace (c) shows that extracellular Mg 2+ fails to elicit a responεe in an oocyte injected only with the mRNA for the εubεtance K receptor, although εuperfuεion with substance K evokes a reεponεe. Holding potential waε -70 to -80 mV. Fig. 26 iε a graphical repreεentation εhowing that extracellular Ca 2+ elicitε oεcillatory increaεeε in Cl— current in Xenopuε oocyteε injected with human (hyperplaεtic) parathyroid tiεεue poly(A) -mRNA. The oocyte waε teεted for reεponεivity to extracellular Ca 2+ three dayε after injection of 50 ng poly(A) -mRNA. Holding potential waε -80 mV. Fig. 27 iε a graphical repreεentation εhowing the mobilization of mtracellular Ca 2+ in bovine parathyroid cells elicited by budmunchiamine. Budmunchiamine (300 μM, structure also shown) was added where indicated. Fig. 28 is a graphical repreεentation εhowing that the ability to mobilize mtracellular Ca 2+ in parathyroid cellε iε stereospecific. Bovine parathyroid cells loaded with fura-2 were initially εuεpended in buffer containing 0.5 M extracellular Ca 2+ before the addition of the indicated concentration of each molecule. Fig. 29 iε a graphical repreεentation εhowing effectε of La 3+ on [Ca2+]. in oεteoclaεts. A representative trace from a single rat osteoclast loaded with indo-1 is shown. At low concentrationε, La 3+ partially blockε increaεeε in [Ca 2+]., elicited by extracellular Figε. 30A and B are graphical repreεentationε εhowing the mobilization of mtracellular Ca 2+ elicited by extracellular Mn 2+ in rat oεteoclaεtε. Extracellular Mn2+ evokeε concentration-dependent increaεeε in [Ca 2+]• (Fig. 30A) that perεiεt m the absence of extracellular Ca 2+ (Fig. 30B) Figs. 31A and 31B are graphical repreεentationε εhowing mobilization of [Ca 2+]. in rat oεteoclaεtε elicited by a molecule termed NPS 449 (εee Fig. 38). Iεolated rat oεteoclaεtε loaded with indo-1 were superfused with the indicated concentrations of NPS 449 in the presence (Fig. 31A) or absence (Fig. 31B) of 1 mM extracellular CaCl,. Fig. 32 is a graphical representation showing the mobilization of mtracellular Ca 2+ in C-cells evoked by NPS 019 (see Fig. 1). rMTC 6-23 cells were loaded with fura-2 and bathed in buffer containing 0.5 mM [Ca 2+]. Where indicated, NPS 019 was added to a final concentration of 10 μM. Representative traces show that the tranεient increaεe in [Ca 2+]. elicited by NPS 019 iε refractory to inhibition by La 3+ (middle trace) and perεiεtε in the abεence of extracellular Ca2+ (right trace). Fig. 33 is a graphical representation showing that NPS 456 (Fig. 36) evokeε oscillatory increases in Cl ~ current in Xenopus oocytes which have been injected with bovine parathyroid cell poly(A) -mRNA. Fig. 34 is a graphical representation showing that extracellular Ca 2+ evokes oscillatory increaseε in Cl— current in Xenopus oocytes which have been injected with human osteoclaεt mRNA. The oocyte waε teεted for reεponsivity to extracellular Ca 2+ three days after injection of 50 ng of total poly(A) + mRNA. Fig. 35 is a graphical representation showing that the parathyroid cell Ca 2+ receptor is encoded by mRNA m a size range of 2.5-3.5 kb. Bovine parathyroid cell poly(A) -mRNA was size fractionated on glycerol gradients and pooled into ten fractions. Each fraction was injected (50 ng/fraction) separately into Xenopus oocytes. After three days, the oocyteε were examined for their ability to respond to neomycin B (lOmM) with oscillatory increaεeε in the Cl- current. Fig. 36 εhowε the chemical εtructures of molecules derived from diphenylpropyl-α-phenethylamine illustrating a family of molecules which were prepared and εcreened to find the uεeful moleculeε of the invention. Fig. 37 is a graphical representation showing that NPS 021 is a calcilytic compound that blocks the effects of extracellular Ca 2+ on [Ca2+]. in bovine parathyroid cellε. Cellε were initially bathed in buffer containing 0.5 mM CaCl 2 and, where indicated, the [Ca 2+] waε increaεed to a final of 2mM (left trace). The addition of NPS 021 (200 μM) cauεed no change in [Ca2+]. but inhibited the increaεe in [Ca 2+] . elicited by extracellular Ca2+ (right trace) . Fig. 38 is a graph showing vivo Ca 2+ reεponse to NPS R,S-467. Fig. 39 is a graph showing in vivo PTH reεponεe to NPS R,S-467. Fig. 40 is a graph εhowing m vivo εerum Ca 2+ responεe to 25 mg/kg NPS R,S-467. Fig. 41 is a graph εhowing the in vivo reεponεe of [Ca 2+]■ in bovine parathyroid cells to different enantiomers of NPS 467. Fig. 42 is a graph εhowing the in vivo reεponεe of εerum Ca 2+ in ratε to different enantiomerε of NPS 467. Fig. 43a depictε a reaction εcheme. for the preparation of fendiline or fendiline analogε or derivatives depicted in Figure 36. Fig. 43b depictε a reaction εcheme for the εyntheεis of NPS 467. Fig. 44 depictε a doεe-reεponεe curve εhowing that NPS 467 lowerε εerum ionized calcium in ratε when adminiεtered orally. Fig. 45 is a reεtriction map of the plaεmid containing BoPCaR 1, deposited with the ATCC under accession number ATCC 75416. Fig. 46 is a restriction map of BoPCaR 1. Fig. 47 is a nucleotide sequence corresponding (about 90% accurate) to the 2.2 Kbfragment of BoPCaR 1 sequenced. Calcimimetic and Calcilytic Molecules Calcimimetic and calcilytic molecules useful in the invention are generally described above. These moleculeε SUBSTITUTESHEET ISA/EP can be readily identified uεing εcreening procedures to define molecules which mimic or antagonize the activity of Ca 2+ at Ca2+ receptorε. Exampleε of εuch procedureε are provided below. Theεe exampleε are not limiting in the invention but merely illuεtrate methodε which are readily uεed or adapted by thoεe εkilled in the art. Generally, calcimimetic and calcilytic moleculeε are identified by εcreening moleculeε which are modelled after those described below (called lead molecules). As can be seen below there are several specific calcimimetics and calcilyticε uεeful at variouε Ca 2+ receptors. Derivative molecules are readily designed by standard procedures and tested in one of many protocols known to those skilled in the art. Many molecules may be screened easily to identify the most useful in this invention. Organic cationic molecules which mimic or antagonize the actions of Ca 2+ in other syεtemε contain the requiεite εtructure for activity on a Ca 2+ receptor. Rational design of other useful molecules involves the study of a molecule known to be calcimimetic or calcilytic and then modifying the structure of the known molecule. For example, polyamines are potentially calcimimetic εince εpermine mimicε the action of Ca 2+ in εeveral in vitro εyεtemε. Results show that spermine doeε indeed cauεe changeε in [Ca 2+]• and PTH εecretion reminiεcent of thoεe elicited by extracellular di- and trivalent cationε (εee below). Converεely, Ga 3+ antagonizeε the effectε of Gd3+ on the bovine parathyroid calcium receptor(ε). The experiments outlined below are therefore aimed at demonstrating that this phenomenology, obtained with spermine, involves the same mechanismε uεed by extracellular Ca2+. To do this, the effects of spermine on a variety of physiological and biochemical parameters which characterize activation of the Ca 2+ receptor were assessed. Those moleculeε having εimilar effectε are uεeful in thiε invention and can be diεcovered by εelecting or making molecules having a structure similar to spermine. Once another useful molecule is diεcovered thiε εelection proceεε can be readily repeated. For clarity, below iε provided a εpecific series of screening protocols to identify εuch useful molecules which are active at a parathyroid cell Ca 2+ receptor, or which act aε agoniεtε or antagoniεts of the cellular responεe to changeε in [Ca 2+] . Equivalent assayε can be uεed for moleculeε active at other Ca 2+ receptorε or other inorganic-ion receptorε, or which otherwise mimic or antagonize cellular functions regulated by [Ca 2+] or other ions. These asεayε exemplify the procedureε which are uεeful to find moleculeε, including calcimimetic moleculeε, of thiε invention. Equivalent procedureε can be uεed to find lytic moleculeε, including calcilytic moleculeε, by εcreening for those molecules most antagonistic to the actionε of the ion, including extracellular Ca 2+. In vitro aεεayε can be uεed to characterize the εelectivity, εaturability, and reverεibility of theεe mimeticε and lyticε by εtandard techniqueε. Screening Procedure Generally, bovine parathyroid cellε loaded with fura-2 are initially εuspended in buffer containing 0.5 mM CaCl,. The test subεtance iε added to the cuvette in a small volume (5-15 μl) and any change in the fluorescence signal noted. Cumulative increases in the concentration of the test substance are made in the cuvette until some predetermined concentration is achieved or changes in fluorescence noted. If no changes in fluorescence are noted, the molecule iε conεidered inactive and no further teεting iε performed. In initial εtudieε, e.g. , with polyamine-type moleculeε, moleculeε were teεted at concentrationε aε high as 5 or 10 mM. As more potent molecules are now known (see below), the ceiling concentration is lowered. For example, newer molecules are tested at concentrationε up to 500 μM or leεε. If no changeε in fluoreεcence are noted at thiε concentration, the molecule can be conεidered inactive. Moleculeε cauεing increaεeε in [Ca 2+]• are subjected to additional testing. The two essential characteristicε of the molecule important for itε conεideration aε a calcimimetic molecule are the mobilization of mtracellular Ca 2+ and sensitivity to PKC activators. Moleculeε cauεing the mobilization of mtracellular Ca 2+ i.n a PMA-εensitive manner have invariably been found to be calcimimetic molecules and to inhibit PTH secretion. Additional testing can, if needed, be performed to solidify thiε belief. Typically, all the variouε teεtε for calcimimetic or calcilytic activity (εee above) are not performed. Rather, if a molecule cauεeε the mobilization of mtracellular Ca 2+ in a PMA-εensitive manner, it is advanced to screening on human parathyroid cellε. For example, meaεurementε of [Ca 2+]. are performed to determine the EC 5Q , and to meaεure the - 45 - ability of the molecule to inhibit PTH secretion in human parathyroid cells which have been obtained from patients undergoing surgery for primary or secondary hyperparathyroidism. The lower the EC 5Q or IC 5Q the more potent the molecule as a calcimimetic or calcilytic. Meaεuring [Ca 2+L with fura-2 provides a very rapid means of screening new organic molecules for activity. In a single afternoon, 10-15 molecules can be examined and their ability to mobilize mtracellular Ca 2+ (or not) aεεeεεed. The εenεitivity of any obεerved increaεe in [Ca 2+]. to depreεεion by PMA can alεo be aεεeεεed. Moreover, a εingle cell preparation can provide data on [Ca 2+]., cyclic AMP levelε, IP, and PTH εecretion. A typical procedure iε to load cellε with fura-2 and then divide the cell εuεpenεion in two; most of the cells are used for measurement of [Ca 2+]. and the remainder are incubated with moleculeε to aεεeεs their effects on cyclic AMP and PTH εecretion. Becauεe of the sensitivity of the radioimmunoasεays for cyclic AMP and PTH, both variables can be determined in a single incubation tube containing 0.3 ml cell εuεpenεion (about 500,000 cellε). Meaεurementε of inoεitol phoεphateε are a time-consuming aspect of the εcreening. However, ion- exchange columnε eluted with chloride (rather than formate) provide a very rapid meanε of εcreening for IP_ formation εince rotary evaporation (which takeε around 30 hrε) iε not required. This method allows procesεing of nearly 100 εampleε in a εingle afternoon. Thoεe moleculeε that prove intereεting, as asεeεεed by meaεurementε of [Ca 2+]. , cyclic AMP, IP,/ and PTH are then subjected to a more rigorous analysis by examining formation of various inositol phosphates and assessing their isomeric form by HPLC. Interesting molecules detected in these protocols are then assessed for specificity, e.g. , by examining their effects on [Ca 2+]. in calcitonin-secretmg C-cells using, e.g. , the rat MTC 6-23 cell line. The following is illustrative of methods useful in these screening procedureε. Exampleε of typical reεultε for various test calcimimetic or calcilytic moleculeε are provided in Figε. 2-34. Parathyroid Cell Preparation Parathyroid glandε were obtained from freεhly εlaughtered calveε (12-15 weekε old) at a local abattoir and tranεported to the laboratory in ice-cold parathyroid cell buffer (PCB) which containε (mM) : NaCl, 126; KC1, 4; MgCl 2 , 1; Na-HEPES, 20; pH 7.4; glucoεe, 5.6, and variable amountε of CaCl-, e.g. , 1.25 mM. Human parathyroid glandε, obtained from patients undergoing surgical removal of parathyroid tisεue for primary or uremic hyperparathyroidiεm (HPT), were treated εimilarly to bovine tiεεue. Glandε were trimmed of exceεε fat and connective tiεεue and then minced with a fine εciεsors into approximate cubeε of 2-3 mm. Diεεociated parathyroid cellε were prepared by collagenaεe digestion. Dissociated cellε were then purified by centrifugation in Percoll buffer. The reεultant parathyroid cell preparation waε eεεentially devoid of red blood cellε, adipocyteε, and capillary tissue as asεeεsed by phase contrast microscopy and Sudan black B staining. Disεociated and purified parathyroid cellε were preεent aε εmall cluεterε containing 5 to 20 cells. Cellular viability, aε indexed by excluεion of trypan blue or ethidium bromide, waε routinely 95%. Although cellε can be uεed for experimental purpoεeε at thiε point, physiological responεes (suppreεεibility of PTH secretion and resting levels of [Ca 2+].) are better after culturing the cells overnight. Primary culture also haε the advantage that cellε can be labeled with isotopes to near isotopic equilibrium, aε iε neceεsary for studieε involving measurements of inositol phosphate metabolism (εee below) . After purification on Percoll gradientε, cellε were waεhed εeveral timeε in a 1:1 mixture of Ham'ε F12-Dulbecco'ε modified Eagle'ε medium (GIBCO) εupplemented with 50 μg/ml εtreptomycin, 100 U/ml penicillin, 5 μg/ml gentamicin and ITS . ITS iε a premixed εolution containing inεulin, tranεferrin, εelenium, and bovine serum albumin (BSA)-linolenic acid (Collaborative Research, Bedford, MA) . The cells were then transferred to plastic flaskε (75 or 150 2 cm ; Falcon) and incubated at 37°C in a humid atmoεphere of 5% CO„ . No εerum iε added to theεe overnight cultureε, εince itε presence allows the cells to attach to the plastic, undergo proliferation, and dedifferentiate. Cells cultured under the above conditions were readily removed from the flaεkε by decanting, and εhow the εame viability aε freshly prepared cells. Measurement of Cytoεol c Ca— 2+ Purified parathyroid cells were resuspended in 1.25 mM CaCl 2 -2% BSA-PCB containing 1 μM fura-2-acetoxymethylester and incubated at 37°C for 20 min. The cellε were then pelleted, reεuεpended in the same buffer lacking the ester, and incubated a further 15 min at 37°C. The cells were subsequently washed twice with PCB containing 0.5 mM CaCl 2 and 0.5% BSA and maintained at room temperature (about 20°C). Immediately before use, the cells were diluted five-fold with prewarmed 0.5 mM CaCl 2 ~PCB to obtain a final BSA concentration of 0.1%. The concentration of cells in the cuvette used for fluorescence recording was 1-2 x 10 6 /ml. The fluorescence of indicator-loaded cells was measured at 37°C in a spectrofluorimeter (Biomedical Inεtrumentation Group, Univerεity of Pennεylvania, Philadelphia, PA) equipped with a thermoεtated cuvette holder-and magnetic εtirrer uεing excitation and emiεεion wavelengths of 340 and 510 nm, respectively. This fluoreεcence indicateε the level of cytoεolic Ca 2+ Fluoreεcence εignals were calibrated using digitonin (50 μg/ml, final) to obtain maximum fluorescence (F ) , and EGTA (10 mM, pH 8.3, final) to obtain minimal fluorescence (Fmm. ) , and a disεociation constant of 224 nM. Leakage of dye iε dependent on temperature and most occurs within the first 2 min after warming the cells in the cuvette; dye leakage increases only very slowly thereafter. To correct the calibration for dye leakage, cellε were placed in the cuvette and εtirred at 37°C for 2-3 min. The cell εuεpenεion waε then removed, the cellε pelleted, and the εupernatant returned to a clean cuvette. The εupernatant waε then treated with digitonin and EGTA aε above to obtain aε eεtimate of dye leakage, which iε typically 10-15% of the total Ca 2+-dependent fluoreεcent εignal. Thiε eεtimate waε subtracted from the apparent Fmm. . Measurement of PTH Secretion In most experiments, cellε loaded with fura-2 were uεed in εtudies of PTH secretion. Loading parathyroid cellε with fura-2 doeε not change their εecretory reεponse to extracellular Ca 2+. Cells were suspended in PCB containing 0.5 mM CaCl 2 and 0.1% BSA. Incubations were performed in plaεtic tubeε (Falcon 2058) containing 0.3 ml of the cell εuεpenεion with or without εmall volumeε of CaCl ? and/or organic polycations. After incubation at 37°C for various times (typically 30 min), the tubes were placed on ice and the cells pelleted at 2°C. Samples of the supernatant were- brought to pH 4.5 with acetic acid and stored at -70°C. This protocol was uεed for both bovine and human parathyroid cells. For bovine cells, the amount of PTH in sample supernatantε was determined by a homologous radioimmunoasεay uεing GW-1 antibody or its equivalent at a final dilution of 1/45,000. 125 I-PTH (65-84; INCSTAR, Stillwater, MN) was used as tracer and fractiόnε εeparated by dextran-activated charcoal. Counting of εamples and data reduction were performed on a Packard Cobra 5005 gamma counter. For human cells, a commercially available radioimmunoasεay kit (INS-PTH; Nicholε Inεtitute, Loε Angeleε, CA) which recognizeε intact and N-terminal human PTH waε uεed becauεe GW-l antibody recognizeε human PTH poorly. Meaεurement of cyclic AMP Cellε were incubated aε above for PTH εecretion εtudieε and at the end of incubation, a 0.15 ml εample waε taken and tranεferred to 0.85 ml hot (70°C) water and heated - 50 - at this temperature for 5-10 min. The tubes were subsequently frozen and thawed several times and the cellular debris sedimented by centrifugation. Portions of the supernatant were acetylated and cyclic AMP concentrations determined by radioimmunoassay. Meaεurement of Inoεitol Phoεphate Formation Membrane phoεpholipidε were labeled by incubating parathyroid cellε with 4 μCi/ml 3H-myo-mositol for 20-24 hrε. Cells were then washed and resuεpended in PCB containing 0.5 mM CaCl 2 and 0.1% BSA. Incubationε were performed in microfuge tubeε in the abεence or preεence of variouε concentrationε of organic polycation for different timeε. Reactions were terminated by the addition of l ml chloroform/methanol/12 N HCl (200:100:1; v/v/v) . Phytic acid hydrolysate (200 μl; 25 μg phoεphate/tube) water was then added. The tubes were centrifuged and 600 μl of the aqueous phase was diluted into 10 ml water. Inositol phoεphates were separated by ion- exchange chromatography using AG1-X8 in either the chloride- or formate-form. When only IP, levels were to be determined, the chloride-form was used, whereas the formate form was used to resolve the major inositol phoεphateε (IP 3 , IP 2 , and IP,). For determination of juεt IP 3 , the diluted sample was applied to the chloride-form column and the column waεhed with 10 ml 30 mM HCl followed by 6 ml 90 mM HCl and the IP 3 eluted with 3 ml 500 mM HCl. The laεt eluate waε diluted and counted. For determination of all major inoεitol phoεphateε, the diluted εample waε applied to the formate-form column and IP,, IP 2 , and IP_ eluted εequentially by increaεing concentrationε of formate buffer. The eluted sampleε from the formate columnε were rotary evaporated, the reεidues brought up in cocktail, and counted. The isomeric forms of IP, were evaluated by HPLC. The reactionε were terminated by the addition of 1 ml 0.45 M perchloric acid and εtored on ice for 10 min. Following centrifugation, the εupernatant waε adjuεted to pH 7-8 with NaHC0 3 . The extract waε then applied to a Partiεil SAX anion-exchange column and eluted with a linear gradient of ammonium formate. The various fractions were then desalted with Dowex followed by rotary evaporation prior to liquid scintillation counting in a Packard Tri-carb 1500 LSC. For all inoεitol phoεphate εeparation methodε, appropriate controls using authentic εtandardε were uεed to determine if organic polycationε interfered with the εeparation. If εo, the εampleε were treated with cation-exchange reεin to remove the offending molecule prior to εeparation of inoεitol phoεphateε. Meaεurement of Cytoεolic Ca— 2+ in C-cellε Neoplaεtic C-cellε derived from a rat medullary thyroid carcinoma (rMTC 6-23) obtained from American Type Culture Collection (ATCC No. 1607) were cultured aε monolayerε in Dulbecco'ε Modified Eagle'ε medium (DMEM) pluε 15% horεe εerum in the abεence of antibioticε. For meaεurementε of [Ca 2+]. , the cellε were harveεted with 0.02% EDTA/0.05% trypεin, waεhed twice with PCB containing 1.25 mM CaCl 2 and 0.5% BSA, and loaded with fura-2 aε deεcribed above for parathyroid cellε. Meaεurementε of [Ca 2+] ■ were performed aε deεcribed above with appropriate corrections for dye leakage. easurement of [Ca— 2+]. in Rat Osteoclasts Osteoclasts were obtained from 1-2 day old Sprague-Dawley rats using aseptic conditions. The rat pups were sacrificed by decapitation, the hind legs removed, and the femora rapidly freed of soft tissue and placed in prewarmed F-12/DMEM media (DMEM containing 10% fetal calf serum and antibiotics (penicillin-streptomycin-gentamicin; 100 U/ml-100 μg/ml-100 μg/ml)). The boneε from two pupε were cut lengthwise and placed in 1 ml culture medium. Bone cellε were obtained by gentle trituration of the bone fragmentε with a plaεtic pipet and diluted with culture medium. The bone fragmentε were allowed to settle and equal portionε (about 1 ml) of the medium tranεferred to a 6-well culture plate containing 25 mm glaεε coverεlipε. The cells were allowed to εettle for 1 hr at 37°C in a humidified 5% C0 2 ~air atmoεphere. The coverεlipε were then waεhed 3 timeε with fresh media to remove nonadherent cells. Measurementε of [Ca 2+]. in oεteoclasts were performed within 6-8 hrε of removing nonadherent cellε. Cells attached to the coverslip were loaded with indo-1 by incubation with 5 μM indo-1 acetoxymethyleεter / 0.01% Pluronic F28 for 30 min at 37 C in F-12/DMEM lacking εerum and containing inεtead 0.5% BSA. The coverεlipε were εubεequently washed and incubated an additional 15 min at o 37 C in F-12/DMEM lacking ester before being transferred to a superfuεion chamber mounted on the εtage of a Nikon Diaphot inverted microεcope equipped for microfluorimetry. Oεteoclasts were easily identified by their large size and presence of multiple nuclei. The cells were superfuεed with buffer (typically PCB containing 0.1% BSA and 1 mM Ca2+) at 1 ml/min with or without teεt εubεtance. The fluoreεcence emitted by excitation at 340 nm waε directed through the video port of the microεcope onto a 440 nm dichroic mirror and fluoreεcence intenεity at 495 and 405 nm collected by photomultiplier tubeε. The outputε from the photomultiplier tubeε were amplified, digitized, and εtored in an 80386 PC. Ratioε of fluorescence intensity were used to estimate [Ca ].. Oocyte Expression In additional studieε, Xenopuε oocyteε injected with mRNA from bovine or human parathyroid cells were used in screening protocols, and Cl ~ current measured as an indirect means of monitoring increaseε in [Ca 2+].. The following iε an example to teεt the effect of neomycin. Oocytes were injected with poly(A) -enriched mRNA from human parathyroid tisεue (hyperplaεtic glandε from a case of secondary HPT). After 3 days, the oocytes were tested for their responεe to neomycin. Neomycin B evoked oεcillatory increaεeε in the Cl- current which ceaεed upon εuperfuεion with drug-free εaline (εee Fig. 20). Reεponseε to neomycin B were obεerved at concentrationε between 100 μM and 10 mM. To enεure that the reεponεe evoked by neomycin B waε contingent upon injection of parathyroid mRNA, the effect of neomycin B on currents in water-injected oocytes was determined. In each of five oocytes examined, neomycin B (10 mM) failed to cause any change in the current. About 40% of oocytes are known to respond to carbachol, an effect mediated by an endogenous muscarinic receptor. In five oocyteε examined, one showed inward currents in response to carbachol, and this is shown in the lower trace of Fig. 20. Thus, in cells expressing a muεcarinic receptor coupled to increases in [Ca 2+]. and Cl ~ current, neomycin B fails to evoke a response. This showε that the reεponse to neomycin B depends on expresεion of a εpecific protein encoded by parathyroid cell mRNA. It εuggeεtε quite εtrongly that in intact cellε, neomycin B actε directly on the Ca 2+ receptor to alter parathyroid cell function. Drug Design From Lead Molecules Certain organic molecules mimic or antagonize the action of extracellular Ca 2+ by acti.ng at the Ca2+ receptor as shown herein. The moleculeε teεted, however, are not neceεεarily εuitable aε drug candidateε, but they εerve to demonεtrate that the hypotheεiε underlying Ca 2+ receptor-baεed therapieε iε correct. These molecules can be uεed to determine the εtructural featureε that enable them to act on the Ca 2+ receptor, and thuε to select molecules useful in this invention. An example of one εuch analytical procedure followε: Thiε example iε detailed in the exampleε below, but iε uεed here to demonεtrate the rationale that can be uεed to deεign useful molecules of this invention from lead molecules discuεεed herein. Thoεe in the art will recognize the analytic εtepε defined in the example and that analogouε analyεiε can be conducted on other lead moleculeε until the moεt deεired calcimimetic or calcilytic is defined. Other examples are also provided below. Together the data preεented demonεtrate that uεeful lead moleculeε will have aromatic groupε which are preferably εubεtituted at one or more poεitionε, and may have branched or linear εubεtituted or unεubεtituted alkyl groupε aε deεired. In addition, it iε important to chooεe moleculeε of correct εtereoεpecificity to enεure higher affinity for the deεired Ca 2+ receptor. Theεe data thus point those m the art to appropriate lead moleculeε which can be derivatiεed to find optimum deεired moleculeε of this invention, much as described below. Although structurally diverse, molecules that are tested may have common features that can be studied. In this example, the correlation between net positive charge and potency in mobilizing mtracellular Ca 2+ was tested. Protamine (+21; EC CΛ = 40 nM) was more effective than neomycin B (+6; EC 5Q = 20 μM in human parathyroid cells and 40 μM in bovine parathyroid cells) which was more effective than spermine (+4; EC-,, = 150 μM) in causing 2+ * > the mobilization of [Ca ]. in parathyroid cells. These resultε raiεe the question of whether positive charge alone determineε potency, or if there are other εtructural featureε that contribute to activity on the Ca 2+ receptor. Thiε iε important to determine at the outεet becauεe it profoundly impacts on the view that the Ca 2+ receptor can be targeted with effective and specific therapeutic moleculeε. Thuε, a variety of other organic polycationε related to neomycin B and εpermine can be εtudied to determine the relationεhip between the net poεitive charge of a molecule and itε potency to mobilize mtracellular Ca 2+ The firεt series of molecules studied were the aminoglycosideε. The molecules were examined on bovine parathyroid cells and their EC 's for the mobilization of mtracellular Ca 2+ determined. For the aminoglycosides, the rank order of potency for eliciting cytosolic Ca 2+ transientε waε neomycin B (EC 50 = 20 or 40 μM) > gentamicin (150 μM) > bekanamycin (200 μM) > εtreptomycin (600 μM) . Kanamycin and lincomycin were without effect when teεted at a concentration of 500 μM. The net poεitive charge on theεe aminoglycoεideε at pH 7.3 iε neomycin B (+6) > gentamicin (+5) = bekanamycin (+5) > kanamycin (average +4.5) > εtreptomycin (+3) > lincomycin (+1). Within the aminoglycoεide εerieε, then, there iε some correlation between net positive charge but it is not absolute, and kanamycin, which would be predicted to be more potent than εtreptomycin, iε without activity. Teεting of variouε polyamineε revealed additional and more marked diεcrepancieε between net poεitive charge and potency. Three εtructural claεεeε of polyamineε were examined: (1) εtraight chain, (2) branched chain, and (3) cyclic. The εtructureε of the polyamines tested are provided in Fig. 1. Amongst the straight chain polyamines, spermine (+4; EC 5 - = 150 μM) waε more potent than pentaethylenehexamine (+6; EC 5Q = 500 μM) and tetraethylenepentamine (+5; EC 5Q = 2.5 mM) even though the latter moleculeε have a greater net positive charge. We synthesized some branched chain polyamines that have different numbers of secondary and primary amino groups and thus vary in net poεitive charge. Two of these molecules, NPS 381 and NPS 382, were examined for effects on [Ca 2+]. in bovine parathyroid cells. NPS 382 (+8; EC 50 = 50 μM) was about twice as potent as NPS 381 (+10; EC-,, = 100 μM) even though it containε two fewer positive charges. A similar discrepancy between positive charge and potency was noted in experiments with cyclic polyamines. For example, hexacyclen (+6; C 5Q = 20 μM) was more potent than NPS 383 (+8; EC 5Q = 150 μM) . The resultε obtained with these polyamines εhow that poεitive charge iε not the εole factor contributing to potency. Additional εtudieε provided inεightε into the εtructural featureε of moleculeε that impart activity on the parathyroid cell Ca 2+ receptor. One of the εtructurally important featureε is the intramolecular distance between the nitrogens (which carry the positive charge). Thus, spermine iε 50-fold more potent than triethylenetetramine (EC 5Q = 8 mM) in evoking increaεeε in [Ca 2+] . in bovine parathyroid cellε yet both moleculeε carry a net poεitive charge of +4. The only difference in εtructure between theεe two polyamineε iε the number of methyleneε εeparating the nitrogenε: in εpermine it iε 3-4-3 whereaε in triethylenetetramine it is 2-2-2. This seemingly minor change in the spacing between nitrogens has profound implications for potency and suggeεtε that the conformational relationεhipε of nitrogenε within the molecule are critical. Supporting thiε are reεultε obtained with hexacyclen and pentaethylenehexamine. The former molecule iε εimply the cyclic analog of the latter and containε the same number of methylenes between all nitrogens, yet the presence of the ring structure increaεeε potency 25-fold. Theεe reεultε indicate that poεitive charge per εe iε not the critical factor determining the activity of an organic molecule on the Ca2+ receptor. Another series of experiments reveals the importance of aromatic groups in determining activity on the Ca 2+ receptor. The results were obtained with two arylalkylamines isolated from the venom of the spider Arqiope lobata. Theεe moleculeε, argiotoxin 636 and argiotoxin 659, have identical polycationic portionε linked to different aromatic groupε (Fig. 24). Argiotoxin 659 evoked tranεient increaεeε in [Ca 2+]. in bovine parathyroid cellε when teεted at concentrationε of 100 to 300 μM. In contraεt, argiotoxin 636 waε without effect when teεted at similar concentrations (Fig. 24). The only difference in structure between these two arylalkylamines is in the aromatic portion of the molecules: argiotoxin 659 contains a 4-hydroxyindole moiety whereas argiotoxin 636 contains a 2,4-dihydroxyphenyl group. The net positive charge on these two arylalkylamines is the same (+4), so their different potencieε muεt reεult from the different aromatic groupε. Thiε εhowε that net poεitive charge alone doeε not determine potency. The real importance of theεe findingε, however, iε the discovery that aromatic groups contribute significantly to the ability of molecules to activate the Ca 2+ receptor. Agatoxin 489 (NPS 017) and Agatoxin 505 (NPS 015) both cauεe the mobilization of mtracellular Ca 2+ in parathyroid cellε with EC 5Q 'ε of 6 and 22 μM, reεpectively. The only difference in the εtructure of theεe moleculeε is a hydroxyl group on the indole moiety (Fig. 1). This εhowε that εubεtitutionε on the aromatic region of the molecule can influence potency. This indicateε that further lead molecules to be studied will include thoεe molecules having subεtituted aromatic moietieε, The εtructural features to be varied syεtemati cally from lead moleculeε described herein include (1) net positive charge, (2) number of methyleneε separating nitrogens, and (3) cyclic verεionε of, e.g. , polyamines, with and without changes in methylene spacing and net poεitive charge. In addition εyεtematic variationε in the εtructure and location of aromatic groupε can be examined, e.g. , in a variety of arylalkylamines isolated from the venoms of waεpε and εpiderε; and synthetic molecules can be prepared by the coupling of commercially'available aromatic moieties to the argiotoxin polyamine moiety. The argiotoxin polyamine moiety can be readily coupled to any aromatic moiety containing a carboxylic acid. Thus, it is simple to syεtematically εcreen the hydroxy and methoxy derivativeε of phenylacetic acid and benzoic acid aε well aε the hydroxyindoleacetic acid series. Analogs containing heteroaromatic functionalities can also be prepared and asseεεed for activity. Compariεonε of potency and efficacy among εuch moleculeε will reveal the optimal εtructure and location of the aromatic group at a conεtant positive charge. One of the structural variations on the polyamine motif that seemε to increaεe potency iε the preεence of the cyclic verεion of the εtraight chain- parent molecule. Budmunchiamine A, iεolated from the plant Albizia amara, iε a cyclic derivative of εpermine (Fig. 1). The addition of budmunchi mine A to bovine parathyroid cellε cauεed a rapid and tranεient increaεe in [Ca 2+]. that perεiεted in the absence of extracellular Ca2+ and was blunted by pretreatment with PMA. It therefore causes the mobilization of mtracellular Ca 2+ in parathyroid cells, probably by acting on the Ca 2+ receptor. It iε about equipotent with εpermine (EC 5Q about 200 μM) yet carrieε one less poεitive charge (+3) than doeε spermine. The resultε obtained with budmunchiamine A demonεtrate the predictive power of the εtructure-activity εtudies and the novel structural information to be gained by testing natural products. Thus, screening of natural productε, εelected rationally on the baεiε of the εtructural information iε readily performed e.g. , moleculeε can be εelected on the baεiε of well-eεtabliεhed chemotaxonomic principleε uεing appropriate data bases, εuch as Napralert. For example, macrocyclic polyamine alkaloids derived from papilionoid legumes related to Albizia, such aε Pithecolobium and other plant-derived moleculeε can be εcreened. Fig. 36 provides a second example of a series of molecules which were screened to determine useful moleculeε of thiε invention. Theεe moleculeε were generally derived from fendiline and teεted to determine their reεpective EC 'ε. Moreover, teεting of related moleculeε, εuch aε NPS 447 and NPS 448 revealε εtereoεpecific effectε of molecule εtructure. The moεt active compoundε teεted to date are the novel compoundε deεignated NPS 467 and NPS 568 which have EC 5Q valueε of leεε than 5 μM. Thoεe in the art, by reviewing thiε εerieε of moleculeε, can determine other εuitable derivativeε which can be teεted in the invention. Theεe examples demonstrate the general deεign and εcreening proceεs useful in this invention, and indicate that additional compound and natural product libraries can be εcreened aε deεired by those in the art to determine other useful lead molecules or novel molecules of this invention. Aε diεcuεεed above, exampleε of moleculeε uεeful aε calcimimeticε include branched or cyclic polyamineε, positively charged polyamino acids, and arylalkylamines. In addition, other poεitively charged organic moleculeε, including naturally occurring moleculeε and their analogε, are uεeful calcimimetics. These naturally occurring moleculeε and their analogε preferably have poεitive charge-to-maεε ratioε that correlate with thoεe ratios for the molecules exemplified herein. (Exampleε include material iεolated from marine εpecies, arthropod venoms, terrestrial plants and fermentation broths derived from bacteria and fungi.) It is contemplated that one group of preferred naturally occurring molecules and analogs useful as calcimimetics will have a ratio of positive charge: molecular weight (in daltons) from about 1:40 to 1:200, preferably from about 1:40 to 1:100. More εpecific exampleε of εuch molecules are provided below. Polyamines The polyamines useful as calcimimetics in this invention may be either branched or cyclic. Branched or cyclic polyamineε potentially have higher calcimimetic activity than their εtraight-chain analogε. That iε, branched or cyclic polyamineε tend to have a lower EC n than their correεponding linear polyamineε with the εame effective charge at phyεiological pH (εee Table 1). Table 1 Molecule Net (+) Charge EC, i0 (μM) Neomycin +6 20 or 40 Hexacyclen +6 20 NPS 382 +8 50 NPS 381 +10 100 NPS 383 +8 150 Gentamicin +5 150 Spermine +4 150 Bekanamycin .+5 200 Argiotoxin-659 +4 300 Pentaethylenehexamine (PEHA) +6 500 Streptomycin +3 600 Spermidine +3 2000 Tetraethylenepentamine (TEPA) +5 2500 1,12-diaminododecane (DADD) +2 3000 Triethylenetramine (TETA) +4 8000 "Branched polyamineε" as used herein refers to a chain molecule conεiεting of εhort alkyl bridgeε or alkyl groupε joined together by amino linkageε, and alεo containing points at which the chain branches. These "branch points" can be located at either a carbon atom or a nitrogen atom, preferably at a nitrogen atom. A nitrogen atom branch point is typically a tertiary amine but it may also be quaternary. A branched polyamine may have 1 to 20 branch points, preferably 1 to 10 branch points. Generally, the alkyl bridges and alkyl branches in a branched polyamine are from l to 50 carbon atoms in length, preferably from 2 to 6 carbon atoms. The alkyl branches may also be interrupted by one or more heteroatoms (nitrogen, oxygen or sulfur) or substituted with functional groups such as: halo, including fluoro, chloro, bromo, or iodo; hydroxy; nitro; acyloxy (R'COO-), acylamido (R'CONH-), or alkoxy (-OR'), where R' may contain from 1 to 4 carbon atomε. The alkyl brancheε may alεo be εubεtituted with groups that are positively charged at physiological pH, such aε amino or guanido. These functional substituents may add or change physical properties such as solubility to increase activity, delivery or bioavailability of the molecules. The branched polyamines may have three or more chain and branch termination points. These termination points may be methyl groups or amino groups, preferably amino groups. One preferred group of molecules is the group of branched polyamines having the formula: H 2 N-(CH 2 ) j -(NR i -(CH 2 ) j ) k -NH 2 where k iε an integer from 1 to 10, each j iε the εame or different and iε an integer from 2 to 20, and each R. is the same or different and is selected from the group consiεting of hydrogen and -(CH 2 ) .-NH 2 , where j iε aε defined above, and at leaεt one R. iε not hydrogen. Particularly preferred branched polyamineε of thiε invention are the moleculeε N 1 ,N 1 ,N 5 ,N 10 ,N 14 ,N 14 -hexakiε-(3- aminopropyl) εpermine and N 1 ,N 1 ,N 5 ,N 14 ,N 14 -tetrakiε-(3- aminopropyl)εpermine referred to as NPS 381 and NPS 382, respectively, in Figure 1. "Cyclic polyamines" as used herein refer to heterocycles containing two or more heteroatoms (nitrogen, oxygen or sulfur), at least two of which are nitrogen atoms. The heterocycles are generally from about 6 to about 20 atoms in circumference, preferably from about 10 to about 18 atomε in circumference. The nitrogen heteroatomε are εeparated by 2 to 10 carbon atomε. The heterocycleε may alεo be εubεtituted at the nitrogen εiteε with aminoalkyl or aminoaryl groupε (NH 2 R-) , wherein R is aminoaryl or a lower alkyl of 2 to 6 carbon atoms. Particularly preferred cyclic polyamines of this invention are shown in Figure 1 as hexacyclen (1,4,7,10,13,16-hexaaza-cyclooctadecane) and NPS 383. Polyamino Acidε The polyamino acidε uεeful in thiε invention may contain two or more poεitively charged amino acid reεidueε at phyεiological pH. Theεe poεitively charged amino acidε include hiεtidine, lysine and arginine. These polypeptides will vary in length from 2 to 800 amino acids in length, more preferably from 20 to 300 amino acids in length. These polypeptides may conεiεt of a εingle repeating amino acid reεidue, or may have the variety of a naturally occurring protein or enzyme. The amino acid reεidueε compriεing the polyamino acidε may be any of the twenty naturally occurring amino acidε, or other alternative reεidueε. Alternative reεidues include, for example, the ositionε of this invention may also contain componentε derivatized with a molecule or ion which actε aε a label. A wide variety of labeling moieties can be used, including radioisotopeε, chromophoreε, and fluorescent labels. Radioisotope labeling in particular can be readily detected in vivo. Radioiεotopeε may be coupled by coordination aε cationε in the porphyrin εyεtem. Uεeful cationε include technetium, and indium. In the compoεitionε, the poεitively charged molecule can be linked to or associated with a label. Methods of Syntheεiε Strategieε for the εyntheεeε and the modification of polyamineε involve the uεe of a variety of amine protecting groupε (phthalimido, BOC, CBZ, benzyl, and nitrile) which can be removed εelectively to conεtruct functionalized moleculeε. The εynthetic methods involved are modelled after those uεed to conεtruct argiopineε 636 and 659 and other arylalkylamineε derived from spider venoms. Chain extensionε of 2-4 methyleneε were typically acco pliεhed by alkylation with the correεponding N-(bromoalkyl)phthalimide. A 1:1.2 mixture of amine to the bromoalkylphthalimide waε refluxed in acetonitrile in the preεence of 50% KF on Celite. Chain extenεions were also accompliεhed by alkylation of a given amine with acrylonitrile or ethylacrylate. Reaction progreεε waε monitored by TLC and intermediateε purified on εilica gel uεing combinationε of dichloromethane, methanol, and iεopropylamine. Final productε were purified by cation exchange (HEMA-SB) and RP-HPLC (Vydac C-18). Purity and εtructure verification are accompliεhed by H- and 13 C-NMR and high-reεolution maεε εpectrometry (El, CI and/or FAB) . BOC protecting groupε were added by the treatment of an amine (1° or 2°) with di-tert-butyl dicarbonate in dichloromethane in the preεence of a catalytic amount of dimethylaminopyridine. Benzyl protecting groupε were applied in one of two ways: (1) condensation of a 1 amine with benzaldehyde followed by sodium borohydride reduction or (2) alkylation of a 2° amine with benzylbromide in the presence of KF. Amide linkages and cyclizations were typically performed by the reaction of an amine (1° or 2°) with the N-hydroxyεuccinimide eεter of a given acid. Thiε waε accompliεhed directly (in the caεe of cyclizationε) by treatment of the "amino acid" with dicyclohexylcarbodiimide under dilute conditionε. Deprotectionε of the phthalimido functionality were accomplished by reduction with hydrazine in refluxing methanol. * Deprotections of the BOC- functionality were accomplished in anhydrous TFA. Deprotection of benzyl, nitrile, and CBZ protecting functionalities was accomplished by reduction in glacial acetic acid under 55 psi hydrogen in the preεence of a catalytic amount of palladium hydroxide on carbon. Nitrile functionalitieε (in the preεence of benzyl and CBZ groups) were selectively reduced under hydrogen in the presence of sponge Raney nickel. Specifically, branched polyamines are typically prepared from simple diaminoalkanes of the formula NH„- (CH 2 ) -NH 2 , or εimple polyamineε εuch aε εpermidine or εpermine. One of the two primary (terminal) amineε iε protected or "maεked" with a protecting group εuch aε BOC (t-butyloxycarbonyl) , phthalimido, benzyl, 2- ethylnitrile (the Michael condenεation production product of an amine and acrylonitrile), or amide. A typical reaction iε the addition of a BOC protecting group by treatment with di-t-butyl-dicarbonate (BOC anhydride) : BOC an vd f H 2 N- CH 2 ) ϊr H80C H^ -^CH≤JH-N^ BOC anhγd f ^_ + 80CH -(CH2)H-WH80C The monoprotected product iε εeparated from the unprotected and diprotected productε by εimple chromatographic or distillation techniques. The remaining free amine in the monoprotected product is then selectively alkylated (or acylated) with an alkylating (or acylating) agent. To ensure mono- alkylation-, the ' free amine- is partially protected by condenεation with benzaldehyde followed by εodium borohydride reduction to . form the N-benzyl derivative: The N-benzyl derivative iε then reacted with the alkylating agent. A typical alkylating agent is in an N-(bromoalkyl)phthalimide, which reacts as follows: KF-Cetøe ACN Redux For example, N-(bromobutyl)phthalimide is used to extend or branch the chain with four methylene units. Alternatively, reaction with acrylonitrile followed by reduction of the cyano group will extend the chain by three methylenes and an amino group. The protecting groups of the resulting chain- extended molecule can then be selectively cleaved to yield a new free amine. For example, trifluoroacetic acid is used to remove a BOC group; catalytic hydrogenation is used to reduce a nitrile functionality and remove a benzyl group; and hydrazine is used to remove phthalimido groups as follows: Hydrazine The new free amine may be alkylated (or acylated) further as above to increaεe the length of the polyamine. Thiε proceεε iε repeated until the deεired chain length and number of brancheε iε obtained. In the final εtep, deprotection of the product results in the desired polyamine. However, further modifications may be effected at the protected end prior to deprotection in the following manner: For example, prior to BOC-deprotection, the polyamine iε acylated with the N-hydroxyεuccinimide ester of 3,4-dimethoxyphenylacetic acid to yield a diprotected polyamine: H _,N-R-NH80C This ultimately will yield an arylalkyl polyamine. The BOC group can then be selectively removed with trifluoroacetic acid to expose the other amino terminus which can be extended as above. Certain branched polyamines may be formed by simultaneouεly alkylating or acylating the free primary and εecondary amines in a polyamine formed as above. For example, treatment of spermine with excess acrylonitrile followed by catalytic reduction yields the following: Cyclic polyamines may be prepared as above beginning with starting materials such as hexacylen (Aldrich Chem. ) . The polyamino acids within the scope of the preεent invention can be made by recombinant techniqueε known in the art, or may be εyntheεized uεing εtandard εolid-phaεe techniqueε known in the art. Solid-phaεe εynthesiε iε commenced from the carboxy-terminal end of the peptide uεing an μ-amino protected amino acid. BOC protective groupε can be uεed for all amino groups even through other protective groupε are suitable. For example, BOC-lys-OH can be esterified to chloromethylated polystyrene resin εupportε. The polyεtyrene reεin εupport iε preferably a copolymer of εtyrene with about 0.5 to 2% divinylbenzene aε a croεs-linking agent which causes the polystyrene polymer to be completely insoluble in certain organic solvents. See Stewart et al., Solid-Phase Peptide Synthesiε (1969), W.H. Freeman Co., San Francisco; and Merrifield, J■ Am. Chem. Soc. (1963) JS5_:2149-2154. These and other methods of peptide syntheεiε are alεo exemplified by U.S. Patent Noε. 3,862,925; 3,842,067; 3,972,859; and 4,105,602. The polypeptide εynthesis may uεe manual techniques or automatically employing, for example, an Applied Biosyεtemε 403A Peptide Syntheεizer (Foεter City, California) or a Bioεearch SAM II automatic peptide synthesizer (Biosearch, Inc., San Rafael, California), following the inεtructionε provided in the inεtruction manual εupplied by the manufacturer. The arylalkylamineε of the invention are natural productε iεolated by known techniqueε, or εyntheεized aε described in Jasyε et al. , Tetrahedron Lett. (1988) 2^:6223-6226, and Naεon et al. , Tetrahedron Lett. (1989) 3_0:2337-2340. One general protocol for preparation of fendiline (or fendiline analogε εhown in Fig. 36) iε aε followε. In a 10 ml round bottom flaεk equipped with a magnetic εtir bar and rubber εeptum, 1.0 mmole 3,3'- biεphenylpropylamine (or primary alkyl amine) in 2 ml ethanol waε treated with 1.1 mmole phenol and 1.0 mmole acetophenone (or substituted acetophenone) . To this was added 2.0 mmoleε MgSO. and 1.0 mmole NaCNBH_ . Thiε was stirred under a nitrogen atmosphere at room temperature (about 20°C) for 24 hrs. The reaction was poured into 50 ml ether and washed 3 times with 1 N NaOH and once with brine. The ether layer was dried with anhydrouε 2 C0 3 and reduced in vacuo. The product waε then purified by column chromatography or HPLC incorporating oεilica εtationary phaεe with combinationε of CH 2 C1 2 - Methanol- iεopropylamine (typically 3% Methanol and 0.1% iεopropylamine in methylene chloride). A preferred procedure for preparing fendiline or fendiline analogs (such aε thoεe depicted in Figure 36) uεes titanium(IV) isopropoxide and waε modified from methodε deεcribed in ___ Org. Chem. 5_5:2552 (1990). For the εyntheεiε of NPS 544, titanium tetrachloride (method deεcribed in Tetrahedron Letterε 3_1:5547 (1990)) waε used in place of titanium(IV) isopropoxide. The reaction scheme is depicted in Figure 43a. In Figure 43a, R,R' and R" depict hydrocarbyl groups. According to one embodiment, in a 4 ml vial, 1 mmole of amine ( 1 ) (typically a primary amine) and 1 mmole ketone or aldehyde (2) (generally acetophenone) are mixed, then treated with 1.25 mmoles titanium(IV) isopropoxide (3_) and allowed to stand with occasional stirring at room temperature for about 30 minutes. Alternatively, a secondary amine may be used in place of ( l ) . Note: some reactions will give heavy precipitates or solids which are warmed/heated (to their melting point) to allow for stirring/mixing several times over the course of the reaction. The reaction mixture is treated with 1 ml ethanol containing 1 mmole εodium cyanoborohydride (4_) and the reεulting mixture iε then allowed to εtand at room temperature with occasional stirring for about 16 hours. After this time the reaction is quenched by the addition of about 500 μl water. The reaction mixture iε then diluted to about 4 ml total volume with ethyl ether and then centrifuged. The upper organic phaεe is removed and reduced on a rotavapor. The resulting product, ( 6 ) , is partially purified by chromatography through a short column of silica (or alternatively by using preparative TLC on silica) using combination of dichloromethane:methanol :isopropylamine (typically 95:5:0.1), prior to purification by HPLC (normal phaεe uεing εilica with dichloromethane:methanol: iεopropylamine or reverεed phase, C-18 with 0.1% TFA with acetonitrile or methanol). If appropriate or desired, chiral resolution may be accomplished using methods such aε thoεe deεcribed in Example 21 ' . Formulation and Admmiεtration Aε demonεtrated herein, the moleculeε of the invention may be uεed to: (a) mimic or antagonize one or more of the effect of an extracellular ion, including extracellular Ca 2+; (b) affect the extracellular free Ca 2+ level in an individual; and (c) treat diεeaεes such as hyperparathyroidism, osteoporosiε and hypertenεion. In general, diεeaεeε or conditionε involving inorganic-ion receptorε now can be εtudied, diagnoεed and/or beneficially treated. While the moleculeε have generally been εhown to have an effect on parathyroid cellε, they may alεo modulate the Ca 2+ receptorε on other cellε, including bone osteoclaεtε, juxtaglomerular kidney cellε, proximal tubule kidney cellε, diεtal tubule kidney cell, cell of the thick ascending limb of Henle's loop and/or collecting duct, keratinocyte in the epidermiε, parafollicular cell in the thyroid (C-cellε), inteεtinal cell, trophoblaεt in the placenta, platelet, vaεcular εmooth muscle cell, cardiac atrial cell, gastrin and glucagon εecreting cellε, kidney meεangial cell and mammary cell. While theεe moleculeε will typically be uεed in therapy for human patientε, they may be uεed to treat εimilar or identical diεeases in other warm-blooded animal εpecieε εuch aε other primates, farm animals such as swine, cattle, and poultry; and sportε animalε and petε εuch aε horεeε, dogε and catε. In therapeutic and/or diagnoεtic applicationε, the moleculeε of the invention can be formulated for a variety of modeε of adminiεtration, including εyεtemic and topical or localized adminiεtration. Techniqueε and formulations generally may be found in Remington's Pharmaceutical Sciences, Mack Publishing Co., Easton, PA. For systemic administration, oral administration is preferred. Alternatively, injection may be used, e.g. , intramuscular, intravenous, intraperitoneal, and subcutaneouε. For injection, the moleculeε of the invention are formulated in liquid εolutionε, preferably in phyεiologically compatible bufferε such as Hank'ε εolution or Ringer ' ε εolution. In addition, the moleculeε may be formulated in εolid form and rediεεolved or εuεpended immediately prior to uεe. Lyophilized formε are also included. Systemic administration can also be by transmucosal or tranεdermal meanε, or the moleculeε can be adminiεtrated orally. For tranεmucoεal or tranεdermal adminiεtration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrantε are generally known in the art, and include, for example, for tranεmucoεal administration bile salts and fusidic acid derivatives. In addition, detergents may be used to facilitate permeation. Transmucoεal administration may be through nasal sprayε, for example, or uεing εuppoεitorieε. For oral adminiεtration, the moleculeε are formulated into conventional oral adminiεtration formε εuch as capsules, tablets, and tonics. For topical adminiεtration, the moleculeε of the invention are formulated into ointmentε, εalveε, gelε, or creams, as is generally known in the art. As shown in the examples below, the amounts of various compounds of this invention which must be :administered can be determined by standard procedures. Generally it is an amount between about 1 and 50 mg/kg animal to be treated. Recombinant Receptors Natural product εcreening haε traditionally provided the lead εtructureε for the development of diverεe therapeutic moleculeε. However, high-throughput εcreening of natural product librarieε or other molecule librarieε for activity on the Ca 2+ receptor haε not previouεly been poεεible. To achieve thiε capability, it iε beεt to clone the Ca 2+ receptor cDNA and then create transfected cell lines suitable for high-throughput screening. The εtructure of the receptor can additionally be uεed to gain inεight into the molecular geometry of the ligand binding site(s), and εuch information uεed to augment a rational drug deεign program aε diεcuεεed above. Limited εtructure-activity εtudieε and testing of selected natural product moleculeε will provide the initial εtructural data baεe neceεεary to guide rational natural product εcreening and drug deεign. The diεcovery of a superfamily of genes permitε the εame advantageε in connection with all inorganic-ion receptors. Although the following discuεεion will refer often to methodology for cloning a calcium receptor, it will be underεtood by thoεe of ordinary εkill in the art that the methodology generally iε applicable to the cloning of all inorganic-ion receptorε. These recombinant receptors allow for the first time screening mimics and lytics, including calcimimetics and calcilytics. For example, by binding asεayε with the receptorε. Thiε iε particularly uεeful in εcreening with the human- receptors ^ in order to identify therapeutically uεeful compoundε. The bovme and human parathyroid cell Ca 2+ receptor cDNA can be cloned by functional expreεεion in Xenopuε oocyteε. It iε poεεible to monitor an increaεe in mtracellular Ca 2+ i.n Xenopuε oocyteε i.ndi.rectly by meaεuring current through the endogenouε Ca 2+-activated Cl ~ channel. The amplification of the reεponεe afforded by thiε εignal tranεduction pathway enableε the detection of receptor proteinε encoded by mRNA at very low levelε. Thiε allowε the detection of receptor- εpecific cDNA cloneε without the need for high affinity ligandε, εpecific antiεera, or protein or nucleic acid sequence information. An example of such a procedure followε. Adult female Xenopuε laeviε were obtained from Xenopuε I (Ann Arbor, MI) and maintained according to εtandard procedureε. Lobeε of ovary were excised from hypothermically-anesthetized toads. Clusterε of oocytes were transferred into modified Barth's saline (MBS). Individual oocytes were obtained by incubation in MBS containing 2 mg/ml collagenase (Sigma, Type 1A) for 2h at 21°C and stage V-VI oocytes were selected for injection. Glass capillary tubes (1 mm diameter) were pulled to a fine tip and manually broken to achieve a tip diameter of about 15 μM. A droplet of mRNA (1 ng/nl in diethylpyrocarbonate (DEPC)-treated water) was placed onto parafilm and drawn into the capillary tube by suction. The capillary tube was then connected to a picospritzer (WPI Instrumentε) and the volume of the air-pulεed dropletε adjuεted to deliver 50 ng of mRNA (typically 50 nl). A 35 mm culture dish with a patch of nyl n. stocking fixed to the bottom waε uεed to εecure the oocyteε during injection of mRNA into the vegetal pole. The injected oocytes were placed into a 35 mm culture dish containing MBS, 100 μg/ml penicillin and 100 μg/ml streptomycin and incubated at 18°C for 3 days. Following incubation, an oocyte waε placed into a 100 μl plaεtic chamber and εuperfuεed with MBS at a flow rate of 0.5 ml/min uεing a periεtaltic pump. Teεt moleculeε or inorganic polycationε were added by rapidly moving the tubing into different bufferε. Recording and current-paεεing electrodeε were conεtructed from thin wall capillary tubing pulled to a reεiεtance of 1-3 Mohmε and filled with 3 M KC1. Oocyteε were impaled (in the animal pole) with both electrodeε under microεcopic obεervation and connected to an Axon Instruments Axoclamp 2A voltage-clamp amplifier which was used to set the holding potential (-70 to -80 mV) and to measure the currents that were pasεed to maintain the holding potential. Currentε were recorded directly onto a strip chart recorder. For mRNA preparation, tissue was obtained from calves or patients with secondary HPT undergoing surgical removal of the parathyroid glands. Purified cellε need not be prepared; whole pieceε of gland were uεed to prepare mRNA that directε the expreεεion of the Ca 2+ receptor in Xenopuε oocyteε. Total cellular RNA waε prepared by acid guanidinium thiocyanate/phenol extraction of homogenized glandε. Oligo-dT cellulose chromatography was used to select poly(A) mRNA by εtandard procedures. For size fractionation of mRNA, centrifugation through glycerol gradients waε ' uεed. Th'e mRNA waε denatured with 20 mM methylmercuric hydroxide and loaded (50-100 μg at a concentration of 1 mg/ml) onto a linear 15-30% glycerol gradient prepared in Beckman TLS55 tubeε. Following centrifugation at 34,000 rpm for 16 hrε, 0.3 ml gradient fractionε were collected and diluted in an equal volume of water containing 5mM beta-mercaptoethanol. mRNA was then recovered by two cycles of ethanol precipitation. If desired, the mRNA (50-100 μg of poly(A) ) may be εeparated on a 1.2% agaroεe/6.0 M urea preparative gel, along with a range of RNA εize markerε. Following viεualization of the mRNA by ethidium bromide staining, gel εliceε containing RNA in approximately 1 kb to 2kb εize εtepε are exciεed. mRNA iε recovered from the agaroεe gel εliceε uεing RNAid binding matrix (according to the εupplier'ε εtandard protocol; Stratagene, Inc.) and recovered mRNA fractionε eluted into DEPC-treated water. Amountε of recovered mRNA were quantified by UV abεorbance meaεurement. The εize range of mRNA contained within each fraction of the glycerol gradient was determined by formaldehyde/agarose gel electrophoresis using a small quantity (0.5 μg) of each sample. The integrity of the mRNA was asεeεεed by in vitro tranεlation of each εample. Reticulocyte lyεateε (commercially available kitε; BRL) were uεed to tranεlate 0.05-0.5 μg of each mRNA fraction. The resulting 35S-labelled proteins were analyzed by SDS-PAGE. The intact mRNA was capable of directing the εyntheεiε of proteins of a complete size range, corresponding roughly to the sizeε of the individual mRNA fractionε. A cDNA library waε conεtructed in the vector λ ZAPII, following modificationε of the technique of Gubler and Hoffman. RNA from the fraction(ε) giving the best responεe in the oocyte aεεay waε uεed aε starting material. Firεt-εtrand cDNA εyntheεeε waε primed with an oligo-dT/Notl primer-linker. Second-εtrand εyntheεiε waε by the RNaεe H/DNA Polymeraεe I εelf-priming method. Double-stranded cDNA was blunted with T4 DNA polymerase and EcoRI adaptors blunt-end ligated to the cDNA with T4 ligase. Following NotI digeεtion to cleave the linker, full-length cDNA waε εize-εelected by excluεion chromatography on Sephacryl 500 HA. Firεt-εtrand cDNA waε radiolabeled with α- 32P-dATP, and all εynthesis and recovery εtepε monitored by following the incorporation of radioactivity. Full-length cDNA recovered from the εizing column was ligated to EcoRI/Notl digested λ ZAPII arms. The ligation mix was test packaged with commercially available high-efficiency packaging extract (Stratagene, Inc.) and plated on the appropriate host εtrain (XLl-blue) . The percentage of recombinant phage was determined by the ratio of white-to-blue plaques when the library is plated on IPTG and X-gal. The average insert εize was determined from ten randomly selected clones. Phage DNA "mini-prepε" were digeεted with EcpRI and NotI to releaεe the insert, and the size determined by agarose gel electrophoreεiε. The library conεisted of >90% recombinant phage, and the inεert εize ranged from 1.5 to 4.2 kb. . The recombinant ligation waε packaged in large εcale to generate 800,000 primary cloneε. The packaging mix waε titered and plated at 50,000 plaqueε per--15,.cm plate.. Each, pool ' of 50,000 cloneε' waε eluted in SM buffer and εtored individually. Plate lysate stockε of each of the clone poolε were uεed for εmall-εcale phage DNA preparation. Phage particles are concentrated by polyethylene glycol precipitation, and phage DNA purified by proteinaεe K digeεtion followed by phenol:chloroform extraction. Twenty microgramε of DNA are digeεted with NotI, and uεed aε template for in vitro tranεcription of εenεe-εtrand RNA. In vitro transcription is according to standard protocols, utilizing T7 RNA 7 polymeraεe and 5' cap analog m GpppG in a 50 μl total reaction volume. Following Dnaεe I/Proteinaεe K digeεtion and phenol/chloroform extraction, the RNA iε concentrated by ethanol precipitation and uεed for oocyte injection. Oocyteε were injected with εynthetic mRNA (cRNA) from each of the 16 library εubpoolε conεtituting 50,000 independent cloneε each. After incubation for 3 to 4 dayε, oocyteε were aεεayed for the ability of 10 mM neomycin to elicit a Ca 2+-dependent Cl-current. A pool deεignated "pool 6" gave a positive signal and thus contains a cDNA clone encoding a functional calcium receptor. In order to decrease the complexity of pool 6 and thus proceed towards the purification of the calcium receptor clone contained within this pool, pool 6 phage were replated at μ20,000 plaques per plate and 12 plates harvested. DNA was prepared from each of these εubpoolε and cRNA εyntheεized. Again, oocyteε were injected with cRNA and aεεayed 3-4 dayε later 2-ι— for the ability of 10 mM neomycin to elicit a Ca dependent Cl-current. A εubpool pool 6-3 waε poεitive and thiε pool waε εubjected to a further round of plating, reducing the complexity of pools to around.5,000 cloneε per pool. Poolε were again aεεayed by preparation of cRNA and injection in oocytes. A subpool pool 6-3.4 was positive. In order to expedite further purification of the positive clone in pool 6-3.4, phage DNA from thiε pool waε reεcued as plasmid DNA by εuperinfection with the helper phage, ExAεεiεt (Stratagene) . Tranεfection of reεcued plaεmids into bacterial strain DH5alphaF' resulted in transformed bacterial colonies on ampicillin plates. These were harvested in pool of 900 clones each. Plasmid DNA was then prepared from each subpool and cRNA syntheεized and aεsayed in the usual manner. Subpool 6-3.4.4 was positive. Bacteria containing the plasmid subpool 6-3.4.4 were εubεequently plated in εubpoolε of μ50 cloneε each. Continuation of thiε proceεε iε expected to reεult in a εingle clone encoding a functional calcium receptor. Alternative aεεayε are available for detecting expreεεion of a calcium receptor in oocyteε. For example, oocyteε can be loaded with 45Ca++ and then treated with - 81 - a calcimimetic. Mobilization of 45Ca++ from mtracellular stores resultε in a net increase in 45Ca++ efflux which is readily determined. Fluorescent Ca indicatorε may alεo be injected into oocyteε. In this case, oocytes expresεing a calcium receptor will exhibit increased fluoreεcence upon activation with a calcimimetic. These asεayε may be employed for cloning calcium receptorε in place of the electrophyεiological aεsay for calcium induced Cl ~ current described in the above example. In addition, the calcimimetic ligand uεed in the cloning procedure need not be neomycin aε indicated above but could inεtead be, for example, Gd , Ca , Mg or other calcimimetic compound. Initial experimentε uεed Xenopus oocytes injected with water or poly(A) -enriched mRNA (50 ng) from bovine parathyroid cellε. After three dayε, the oocyteε were examined for their ability to increaεe mtracellular Ca 2+ in reεponεe to increases in the concentration of extracellular di- and trivalent cations. The oocytes were impaled with recording and current-pasεing electrodeε and [Ca 2+]■ was asεeεεed indirectly by meaεuring currentε through the endogenouε Ca 2+-acti.vated Cl- channel. In oocyteε injected with poly(A) -enriched mRNA from bovine (or human, Fig. 26) parathyroid cellε, increasing the concentration of extracellular Ca 2+ from 0.7 to 3, 5 or 10 mM caused a rapid and tranεient increase in the Cl ~ current which then oscillated around a higher basal current. Increasing the concentration of extracellular Mg 2+ from l to 10 mM likewise evoked oscillatory increaseε in Cl ~ current. The Cl ~ current reεponεe to extracellular Mg2+ persisted when the extracellular Ca2+ concentration waε reduced to < 1 μM (Fig. 25). The impermeant trivalent cation Gd 3+ (600 μM) alεo cauεed oεcillatory increaεeε in the Cl ~ current (Fig. 25). Such increaεeε in the Cl ~ current which oscillate and persiεt in the nominal abεence of extracellular Ca 2+ are noted when oocyteε have been allowed to express other Ca 2+-mobilizing receptors and are εtimulated with the appropriate ligand (e.g. , εubεtance K, Fig. 25) . In theεe inεtanceε, the increaεe in Cl- current reflectε the mobilization of mtracellular Ca 2+. Theεe initial εtudieε likewiεe εhow that ' extracellular polycationε mobilize i mnttrraaccee.llular Ca 2+ in parathyroid cell mRNA-mj ected oocyteε Oocyteε injected with water did not show any change in the Cl — current when exposed to extracellular Ca2+ (10 mM) or Mg 2+ (20 or 30 mM) . In one seπeε of experiments, oocytes were injected with the mRNA encoding the substance K receptor. In these oocytes, extracellular Mg 2+ (20 mM) did not evoke any current but the cells responded vigorouεly to the addition of εubεtance K (Fig. 25). Theεe experimentε indicate that there iε no endogenous sensitivity of the oocyte to extracellular Ca 2+ or Mg2+ Similar experimentε were performed uεing oocyteε injected with poly(A) -enriched mRNA prepared from human parathyroid glandε (hyperplaεtic tissue from a case of secondary HPT). In these oocytes, increasing the concentration of extracellular Ca 2+ cauεed a reversible increase in the Cl ~ current which oscillated (Fig. 26). The addition of 300 μM La 3+ likewise caused oεcillatory increases in the Cl current. Increasing the concentration of extracellular Mg 2+ from 1 to 10 mM evoked increaseε in the Cl ~ current that perεiεted in the abεence of extracellular Ca 2+. Additional experimentε suggest that the responεe to extracellular Ca 2+ lε concentration dependent. Thuε, in three mRNA-injected oocyteε, Cl current increaεed to a maximum of 111 + 22 nA at 3 mM and 233 + 101 nA at 10 mM extracellular Ca 2+ The reεults obtained in Xenopus oocytes demonstrate the preεence of a mRNA(ε) in parathyroid cellε encoding a protein(ε) which can impart, in normally unreεponεive cells, senεitivity..to extracellular Ca 2 . +. Moreover, the ability of extracellular Mg 2+ to evoke oεci.llatory increaεeε in Cl - current m the abεence of extracellular Ca2+ demonεtrateε that the Cl- current dependε on the mobilization of mtracellular Ca 2+ rather than influx of extracellular Ca 2+. The reεultε obtained with La3+ likewiεe εhow that the expreεεed protein(ε) iε linked to the mobilization of mtracellular Ca 2+. Together, theεe data εhow that the expreεεed protein(ε) actε aε a cell εurface receptor rather than a channel . Theεe εtudieε provide compelling evidence for the exiεtence of a Ca 2+ receptor protein on the εurface of parathyroid cellε and demonεtrate the feaεibility of uεing the Xenopuε oocyte εyεtem to achieve the molecular cloning of the Ca 2+ receptor cDNA. In another εerieε of experimentε, parathyroid cell mRNA waε εize fractionated by centrifugation through a glycerol gradient. Ten fractionε were collected. Each group was injected into Xenopus oocyteε and after a three day incubation period the oocyteε were aεεayed for expression of the Ca2+ receptor. Those oocytes injected with fractions 4-6 showed the largest and most consiεtent increaεeε in Cl ~ current in reεponεe to extracellular Ca 2+ (Fig. 35). Theεe reεultε indicate that the Ca2+ receptor iε encoded by mRNA in a εize range of 2.5-3.5 kb. Thiε indicateε that a εtrategy uεing direct expreεεion of RNA εynthesized from a transcription vector cDNA library is feasible. Size-fractionation experimentε of thiε εort were conducted and in each of three different fractionation experimentε εimilar reεultε were obtained. The mRNA fractionε obtained and characterized in the preceding, experiments can be aεεayed by injection into oocyteε. For each mRNA fraction, 10-20 oocyteε are injected with 50 ng of RNA at a concentration of 1 ng/nl in water. Injected oocyteε are maintained at 18 C for 48-72 h after which they are aεεeεsed for expresεion of the Ca 2+ receptor uεing meaεurementε of Cl current. For each group of injected oocyteε the number poεitive for expreεεion of the receptor, aε well aε the magnitude of the Ca 2+-dependent Cl- current meaεured, l.ε determi.ned. Aε negative controlε, oocyteε are injected with rat liver poly(A) -enriched mRNA, yeaεt RNA, or water. It iε expected that an mRNA in the range of 2.5 - 3.5 kb will encode the receptor. mRNA of a larger εize may neceεεitate a cloning approach baεed on hybrid depletion of parathyroid mRNA prior to oocyte injection. Thiε εtrategy iε not dependent upon the generation of full-length cDNA cloneε for succesε. If receptor expreεεion iε not obtained with a εingle εize fraction of mRNA, oocyteε are injected with mixed εize fractionε to determine a combination that doeε give riεe to a functional receptor. If it doeε appear that multiple subunits are neceεεary for the formation of a functional receptor, the hybrid depletion expression cloning strategy iε uεed. In thiε approach, cloneε are selected on the basiε of their ability to deplete a specific mRNA specieε from the total mRNA population. A clone encoding a εingle εubunit iε identified by itε ability to prevent the formation of the active multi-εubunit complex. By exhaustive screening it is posεible to identify cloneε encoding all of the neceεεary εubunitε. Thiε approach permits the isolation of clones encoding individual subunits required to form a' functional receptor complex. Synthetic RNA from pools of clones are aεεayed for their ability to induce expression of the Ca 2+ receptor in Xenopus oocytes by the same techniques used to analyze the original mRNA fractions. Originally, 10 pools representing 100,000 primary clones each are examined. Pools of clones showing a positive reεponεe are screened at lower (typically 4-to-10 fold) complexity, and again positive pools further subdivided and screened. Thiε proceεε of library εub-fractionation iε followed until individual poεitive cloneε are identified. Aε a negative control for the oocyte expreεεion aεεay, anti-εenεe tranεcriptε are generated from those DNA templates that induce a positive reεponεe. Anti-sense transcripts are unable to give rise to an authentic receptor, and thiε will control any non-εpecific poεitive εignal ariεing from injection of εynthetic RNA. Another concern iε the fact that εynthetic RNA can occaεionally "poiεon" tranεlation in injected oocyteε, by an undefined mechaniεm. To control for this possibility, synthetic RNAs giving a negative response are co-injected at various dilutions with parathyroid cell mRNA, to determine if they are non-specifically interfering with the expresεion of the Ca 2+ receptor. When an individual clone encoding the Ca 2+ receptor iε identified, the cDNA insert will be excised from the vector and used for large scale production of synthetic RNA. Oocyte injection of this single RNA specieε allowε rigorouε aεεeεεment of the characteristics of the expresεed receptor. If the εize of the mRNA encoding the Ca 2+ receptor iε too large for cloning by direct transcription and expresεion, or if multiple εubunitε are involved, a hybrid-depletion technique of εcreening poolε of cloneε iε uεed. cDNA inεert DNA will be prepared from poolε of cloneε from the εize-εelected parathyroid cell cDNA library. Thiε DNA iε hybridized to parathyroid cell mRNA under conditionε that permit the formation of DNA/RNA duplexeε. The unannealed, hybrid-depleted RNA iε recovered and uεed for oocyte injectionε. Other methodε for hybrid-depletion or hybrid-arrest may be used alternatively and are well known by those skilled in the art. DNA from poolε of cloneε contai .ni.ng εequenceε representi.ng Ca2+-receptor mRNA is depleted from this mRNA from the total parathyroid cell mRNA population, and expresεion of the receptor is reduced or abεent upon oocyte injection. A proceεε of εub-fractionation iε followed on poolε of cloneε of decreaεing complexity, at each εtep aεεaying for cloned DNA that depleteε Ca 2+ receptor-encodmg mRNA from the total parathyroid cell mRNA population. The uεe of an internal control during the hybrid depletion aεεayε enεureε that the hybrid-depleted RNA iε intact and capable of being tranεlated in the oocyte. Human parathyroid cellε expreεs a beta-adrenergic receptor coupled to adenylate cyclase. Thiε receptor can be expreεεed in oocyteε, where it iε capable of agonist-induced activation of the endogenous adenylate cyclase. During the hybrid-depletion screening for Ca 2+ receptor clones, oocyteε injected with hybrid depleted mRNA are aεεayed for iεoproterenol-induced adenylate cyclaεe activation. A poεitive reεponεe in thiε aεεay εerveε to indicate that any obεerved inhibition of C 2+ receptor reεponεe lε εpecific, and not due to a general inhibition of the total mRNA population. The hybrid-depletion screening strategy can result in the isolation of clones that do not contain a complete protein coding region. Poεitive cloneε iεolated by thiε εcreening εtrategy are εequenced to determine their protein coding capacity. Northern blot analyεiε of human parathyroid gland RNA permitε the determination of the εize of the complete mRNA correεponding to εpecific cloneε. If poεitive cloneε do not appear to be full length, the cloned cDNA will be uεed aε a hybridization probe to εcreen a parathyroid gland cDNA library for complete cDNAε. A variety of cell lineε are capable of coupling exogenouεly expreεεed receptorε to endogenouε functional reεponses. A number of these cell lines (e.g., NIH-3T3, HeLa, NG115, CHO, HEK 293 and COS7) can be tested to confirm that they lack an endogenous Ca 2+ receptor. Those lines lacking a response to external Ca 2+ can be uεed to establish stably transfected cell lines expressing the cloned Ca 2+ receptor. Production of these stable tansfectants is accompliεhed by transfection of an appropriate cell line with a eukaryotic expresεion vector, εuch aε pMSG, in which the coding εequence for the Ca 2+ receptor cDNA has been cloned into the multiple cloning site. These expresεion vectorε contain a promoter region, εuch aε the mouεe mammary tumor viruε promoter (MMTV) , that drive high-level tranεcription of cDNAε in a variety of mammalian cellε. In addition, theεe vectorε contain geneε for the εelection of cellε-that stably express the cDNA of interest. The εelectable marker in the pMSG vector encodeε an enzyme, xanthine-guanine phoεphoriboεyl tranεferase (XGPRT), that confers resistance to a metabolic inhibitor that is added to the culture to kill the nontransfected cellε. A variety of expreεεion vectorε and εelection εchemeε are uεually aεεessed to determine the optimal conditionε for the production of Ca 2+ receptor expressing cell lines for use in high throughput screening asεayε. The most effective method for transfection of eukaryotic cell lines with plasmid DNA varies with the given cell type. The Ca 2+ receptor expreεεion construct will be introduced into cultured cellε by the appropriate technique, either Ca 2+ phosphate precipitation, DEAE-dextran transfection, lipofection or electroporation. Cells that have stably incorporated the transfected DNA will be identified by their resiεtance to εelection media, aε deεcribed above, and clonal cell lineε will be produced by expanεion of reεiεtant colonieε. The expression of the Ca2+ receptor cDNA by theεe cell lines will be asεeεεed by εolution hybridization and Northern blot analyεiε. Functional expreεεion of the receptor protein will be determined by meaεuring the mobilization of 2+ intracellular Ca in reεponse to externally applied Ca 2+ receptor agonistε. Cloning the Ca 2+ receptor enables both structural and functional studieε of thiε novel receptor. Recombinantly produced receptor may be cryεtallized for εtructural εtudies. Stably transfected cell lines expresεing the receptor can be uεed for high-throughput εcreening of natural product or other compound, libraries. Molecules of the requisite potency and specificity can be labeled (radioactively or fluorescently) . The ability of teεt moleculeε/extractε to diεplace such a labeled molecule will form the basiε of a high-throughput aεεay for εcreening. Another εtrategy for cloning an inorganic-ion receptor in oocyteε iε aε followε. The general procedures for isolation, defolliculation and injection of frog oocytes are described below. In brief, Xenopus laevis frogε are aneεthetized by immerεion in 0.17% Tricaine and a lobe of the ovary removed and minced into small pieces. Individual stage V-VI oocytes are isolated uεing an L-shaped capillary tube after incubating the ovarian tissue in a calcium-free buffer at room temperature for 90 min. The separated oocytes [usually 200-300 per experiment] are then incubated in collagenase εolution [Sigma, Type II; 2 mg/ml] for an additional 90 min following which the follicular layer can be removed with fine forcepε. The defolliculated oocyteε are incubated overnight in frog ringer [ND96] at 17°C and degenerating oocytes removed [usually <2-3% of the total]. Surviving oocytes are then injected with 50 nl H 2 0 [control] or poly(A) + RNA[15-50 ng/oocyte; in 50 nl H 2 0] and then incubated for 2-4 dayε at 17°C. (The frog ringer, ND96, containε (mM) : NaCl (96), KC1 (2), CaCl 2 (0.5), MgCl 2 (0.5), HEPES (5), pyruvate (2.5)]. Total RNA iε extracted from the tiεεue [kidney, oεteoclasts, etc.] with guanidinium thiocyanate and separated on a CsCl cuεhion. Poly(A) RNA is then isolated by oligo(dT) celluloεe chromatography [two paεεeε through the column] . The integrity of the poly(A) RNA iε aεεeεεed by agaroεe gel electrophoreεiε. The ability of 25-50 ng of poly(A) +RNA to give rise to Ca2+-dependent Cl— channel activity upon exposure to extracellular Gd 3+ is asεeεsed [i.e., aε evidence for Ca 2+ receptor activity]. The next εtep lε to localize the mRNA expressing Ca 2+ receptor activity to a small size range (~1 kb) . For this purpose, -100 μg of poly(A) RNA is separated by sucroεe gradient and 40 εize fractions collected from the gradient. Alternatively, -200-300 μg of poly(A) RNA can be fractionated by preparative, continuous flow agarose gel electrophoreεiε [Hediger, M.A. : Anal. Biochem. 159-.280-86, (1986) and 70-90 fractionε collected. X. laevis oocytes are injected with pools of fractions [3-5 fractions/pool] of poly(A)+RNA [0.2-0.5 ng/oocyte] fractions from the pool(s) and the ability of theεe poolε to give rise to Ca receptor activity asεeεεed. Individual fractionε from the pool(ε) giving the higheεt Ca 2+ receptor activity are injected into oocytes to define the fraction(s) within thiε pool of poly(A)+RNA that give the highest expresεion of the Ca 2+ receptor in oocyteε. A directional cDNA library iε constructed from this poly(A)+RNA pool using the Superscript Plasmid system [pSPORTl; BRL]. cDNA is generated using the Superscript, MuMLV-RT, reverse transcriptε [many of which will be full-length for the coding region] . cDNA iε εized by gel electrophoreεiε and the appropriate cDNA εize region [baεed on the poly(A)+RNA εize range] iε extracted using GENECLEAN II [Bio 101]. Thiε size selected cDNA is then directionally ligated into the pSPORTl plasmid vector using a Not I primer at the.3 ' end and an adapter for Sal I at the 5' end. The resulting plasmids are introduced into ELECTROMAX DH10B cellε [BRL] by electroporation. The tranεformed bacteria are grown on nitrocelluloεe filters [500-800 colonies/filter] and maεter filterε εtored at 4°C [εhort-term] or -70°C [long-term]. Replicate filterε are grown and plaεmid DNA iε iεolated from the filterε, linearized by reεtriction cutting, and then uεed aε a template for εenεe cRNA εyntheεiε by in vitro tranεcription [T7 promoter in the preεence of Cap-analog] . The poolε of cRNA are individually injected into oocyteε which are aεεayed for expression of Gd 3+-induced [l-100μM] activation of Cl ~ currents. A standard sib selection procedure iε utilized to identify a clone that expreεεeε Ca 2+ receptor acti.vi.ty i.n oocyteε. A reεtriction map of the Ca 2+ receptor cDNA iε generated and εuitable reεtriction fragmentε εubcloned into pSPORTl. Subcloned cDNAε are bidrectionally εequenced uεing εtandard methodε [Sequenaεe Polymeraεe 2® 2, USB]. Sequencing primers (18-mer) are used where necessary to sequence regions within or between subclones or to resolve compresεionε or ambiguouε regions of sequence. The coding region for the Ca 2+ receptor protein is determined from the longest open reading frame that haε a start site preferably homologous with the Kozak consenεuε sequence. Hydropathy and other protein algorithms are uεed to generate a topology for the Ca 2+ receptor protein. The nucleoti .ddee sequence of the cDNA, the amino acid sequence of the Ca.2''+ receptor protein, and the protein topology are compared with that for the other Ca 2+ receptors and other known cDNAs and proteins present in the database. Homologous regions might represent domains involved in cation binding or regulation. The preεently preferred method for iεolating inorganic-ion receptor nucleic acid iε baεed upon hybridization εcreening. Region εpecific primerε or probeε derived from BoPCaR 1 can be uεed to prime DNA εynthesiε and PCR amplification, aε well as to identify colonies containing cloned DNA encoding a member of the inorganic ion receptor family using known methods (Innis et al. , PCR Protocolε, Academic Preεε, San Diego, CA (1990)) . When uεing primerε that are derived from nucleic acid encoding an inorganic-ion receptor, one εkilled in the art will recognize that by employing high εtringency conditions, annealing at 50-60°C, sequenceε which are greater than about 76% homologouε to the primer will be amplified. By employing lower εtringency conditionε, annealing at 35-37°C, sequences which are greater than about 40-50% homologous to the primer will be amplified. When uεing DNA probeε derived from inorganic ion receptorε for colony/plaque hybridization, one εkilled in the art will recognize that by employing high stringency condition, hybridization at 50-65°C, 5X SSPC, 50% formamide, wash at 50-65°C, 0.5X SSPC, εequenceε having regionε which are greater than about 90% homologouε to the probe can be obtained, and by employing lower stringency conditions, hybridization at 35-37°C, 5X SSPC, 40-45% formamide, wash at 42°C SSPC, sequenceε having regionε which are greater than 35-45% homologouε to the probe will be obtained. • Any tissue^can r be used- as the source for. the genomic DNA encoding members of the inorganic-ion receptor family. However, with respect to RNA, the most preferred source iε tiεεueε which expreεε elevated levels of the desired inorganic-ion receptor family member. In the present invention, oocyte injection and two-electrode whole oocyte voltage clamping was used to identify expresεion from εuch a tiεεue εource. However, uεing the εequenceε diεcloεed herein, it iε now possible to identify such cells using the inorganic-ion receptor sequence as a probe in northern blot or in situ hybridization procedures, thus eliminating the necesεity of the procedureε employed to clone the firεt member of thiε family and eliminating the need to obtain RNA from a tissue which expresεeε elevated levelε of inorganic-ion receptor. The preεent invention further provideε methodε of identifying cellε or tissues which express a member of the inorganic-ion receptor family. A probe comprising the DNA εequence, for example, of BoPCaR 1, a fragment thereof, or a DNA sequence encoding another member of the inorganic-ion receptor family of proteins can be used as a probe or amplification primer to detect cells which expresε a meεsage homologous to the probe or primer. One skilled in the art can readily adapt currently available nucleic acid amplification or detection techniques so that it employs probes or primerε baεed on the εequenceε encoding a member of the inorganic-ion receptor family. Given the appropriate cellε or tissues expresεing other receptors, these receptors may be cloned in a manner analogous to that described above for the parathyroid cell calcium receptor. For example, mRNA from human osteoclastoma tisεue encodeε the oεteoclaεt calcium receptor (Figure 34). Thus, to isolate a clone for the human osteoclast receptor, one need only isolate mRNA from osteoclaεtoma tissue, prepared a cDNA library and asεay/fractionate subpools as described above. Furthermore, the preferred receptors for drug screening are of human origin. A clone encoding a receptor from one species may be used to obtain the corresponding human cDNA clone by cross-hybridization as is well known by those skilled in the art. In addition, the clone of the parathyroid cell or other cell receptor allows isolation of genes encoding similar inorganic-ion sensing proteins in other cells, and expresεion of those proteins. This is achieved by a variety of approaches. Southern blot analysis of human genomic DNA, utilizing the Ca 2+ receptor cDNA as a hybridization probe, will give an indication of the number of related sequenceε encoded within the genome; hybridization at varying stringencies will give an indication of the degree of divergence among the related εequenceε. Thiε will provide information about the potential number of genes encoding related receptor proteinε. Northern blot analysis with Ca 2+ receptor cDNA as probe will determine if the same or related transcripts are present in various tissues. If related transcripts homologous to the parathyroid cell Ca 2+ receptor are detected, it is a relatively simple matter to obtain clones of these mRNAε, either by εcreening the appropriate cDNA librarieε or by polymerase chain reaction (PCR) techniques. Targeted gene walking (TGW) is a modification of a standard polymerase chain reaction (PCR) that allows amplification of unknown DNA sequenceε adjacent to short segmentε of known sequence. Parker et al., Nucl. Acids Res. , 1^:3055, (1991). Unlike conventional PCR techniques that amplify DNA sequences between two known primer sites, TGW can amplify DNA adjacent to one such site. Thus, TGW can serve as a replacement for conventional cloning and library screening methods for isolating sequenceε upεtream or downstream from known sequenceε. The procedure can be uεed to iεolate geneε from any εtarting DNA template for which a limited amount of sequence information is known. First, several standard PCR reactions are run in parallel using one "targeted primer" and different "walking primers." The targeted primer is a sequence-specific primer exactly complementary to a known sequence on the DNA molecule of interest, and is directed towards unknown adjacent sequences. The walking primers are non-εpecific εequenceε not complementary to DNA near the target primer. The walking primerε can be any oligonucleotideε unrelated to the target primer εequence. In the firεt series of PCRs, products are produced only when a walking primer anneals to a DNA strand contiguous with and complementary to the strand to which the targeted primer has hybridized. The PCR products of interest are preferably within the 5 kilobase size range. Amplification products are produced with as many as 60% mismatched nucleotides within the walking primer relative to DNA template. Perfect base-pairing is required only for the first two 3' nucleotides of the walking primer, but partial homology is tolerated otherwise. Annealing temperature is a key variable in determining the number of PCR products, as identified by agarose gel electrophoreεis. Second, an oligomer extension asεay iε performed uεing an "internal detection primer." This primer repreεentε known εequenceε between the previous two primers, contiguous with the targeted primer. The internal detection primer is kmased with 32P-gamma-ATP, then uεed in a εingle PCR cycle with DNA from the firεt PCR as template. This extension identifies products in the first PCR contiguous with the targeted primer. These new productε are identified by agaroεe gel electrophoreεiε and autoradiography. Any productε that do no hybridize to the internal detection primer repreεent non-contiguouε amplification productε produced by any εubset of the primers. Last, bands identified in the oligomer extension asεay are excised from the gel, and reamplified by standard PCR uεing target primer and the walking primer that produced the band initially. This new PCR band iε then εequenced directly to provide previouεly unknown εequence information. To extend information in the opposite direction, complements are made of the targeted and internal detection primers, and their order is reversed in the protocol. In performing hybridization screening and cloning, the following should be considered. Since there is degeneracy in the genetic code, more than one codon existε for almoεt all the amino acids (except tryptophan and methionine). Moreover, the frequency of usage of any particular codon is different in non-humans as compared to humans. Taking into account codon degeneracy and human-preferred codons, oligonucleotides are εyntheεized. Moreover, oligonucleotideε with variouε permutationε of poεsible codons are also synthesized. To avoid an excesεive number, not all possible sequences resulting from the degeneracy of the code need be synthesized. Rather, a subset of codons are chosen which have the higheεt frequency of occurrence. Novel receptor cloneε εo obtained can be aεεeεεed functionally by expression, either in oocytes or in transfected cell lines. Transfected cell lineε expreεsing a cell-εpecific inorganic-ion receptor can then provide a meanε of high-throughput εcreening for moleculeε that act εpecifically on the ion-εenεing mechaniεm of, for example, oεteoclaεts or juxtaglomerular cells. In an alternative method, the calcium receptor can be cloned by expresεion in eukaryotic cells. For example, a cDNA library can be prepared from parathyroid mRNA and cloned into a eukaryotic expression vector such as, pCDNAl. Subpools from this library can be tranεfected into eukaryotic cells such as COS7 or HEK293 cells resulting in relatively high-level transient expression of encoded cDNA sequences. Cells transfected with a function calcium receptor clone will express the calcium receptor which can then be activated by calcium, neomycin or other calcimimetic compounds. If cells are first loaded with a fluorometric indicator for [Ca 2+]., activation of the calcium receptor results in increased fluorescence. Thus library subpools containing the calcium receptor are identified by their ability, upon transfection into eukaryotic cells, to induce a calcium or calcimimetic-specific increase in fluorescence. This fluorescence can be detected using either a fluorimeter or a fluoreεcence-activated cell εorter (FACS) . We have alεo developed a "calcium trapping assay" for the detection of COS 7 cells expresεing G-protein coupled receptors. In this assay COS 7 cell monolayers are tranεfected with cDNA cloneε from a bovine parathyroid cDNA library (e.g. , subfractions or pools from a library prepared in pCDNAl) and are asεayed for their ability to trap radioactive 45Ca++ i.n reεponεe to treatment with an agoniεt for the Ca 2+ receptor. The monolayerε undergo emulεion autoradiography and cells that have trapped 45 Ca++ are identified by the presence of photographic grain clusterε under dark-field microεcopy. Library poolε that produce a poεitive εignal are then sequentially subdivided until a single cDNA that produces the signal is identified. The calcium receptors appear to be functionally related to a clasε of receptorε which utilize εo-called "G" proteins to couple ligand binding to mtracellular signalε. Such "G-coupled" receptorε may elicit increaεeε in mtracellular cyclic AMP due to the εtimulation of adenylyl cyclaεe by a receptor activated "G " protein, or elεe may elicit a decrease in cyclic AMP due to inhibition of adenylyl cyclase by a receptor activated "G." protein. Other receptor activated G proteins elicit changes in inositol triεphoεphate levelε resulting in release of Ca from mtracellular stores. This latter mechanism is particularly pertinent to calcium receptors. All known G-coupled receptors are structurally related, having seven conserved transmembrane domainε. A number of such receptors have been cloned based on εequence homology to previouεly cloned receptors. One particularly useful approach iε to employ degenerate primerε homologouε to the conεerved tranεmembrane domain coding regionε and to amplify DNA regionε encoding theεe sequences using polymerase chain reaction (PCR). Thus, such oligonucleotide primers are mixed with genomic DNA or cDNA to RNA isolated from the tisεue of choice and PCR carried out. Some experimentation may be required to specifically amplify novel G-coupled receptor sequenceε from the tiεεue of choice εince theεe are not neceεεarily identical to already known G-coupled receptors but, this is well understood by those εkilled in the art [see for example, Buck, L. and Axel, R. (1991) Cell, 65:175-187]. Calcium receptors may also be cloned by such a PCR approach. Two examples of degenerate oligonucleotide primer pairs which can be used to PCR amplify sequenceε encoding calcium receptorε are given below. The firεt pair iε baεed on the cross-homology exhibited by the majority of G-coupled receptors in the sequences encoding transmembrane domains II and VII respectively. The second primer pair is based on the cross-homology exhibited by a more divergent subgroup of G-coupled receptors which includes the calcitonin, secretin, PTH and GLP receptors. This pair correspondε to conεerved sequences encoding tranεmembrane domainε III and VII. When one or both of theεe two primer pairε are mixed with cDNA from parathyroid or oεteoclast tisεueε, for example, PCR amplification reεultε in the generation of amplified DNAε of about 500 to 800 baεe pairε. Theεe DNAε can be isolated and analyzed for the preεence of calcium receptor εequenceε. For example, each amplified εequence can be uεed aε a probe to iεolate a full-length cDNA clone which can then be aεsesεed in one or more of the aεsays indicated above to determine if an inorganic-ion receptor iε encoded. PRIMER PAIR 1: 5' GACTACTTCCTGGTGAACCTGGC 3 ' A T T T C C C 5 ' TCAAIGAGCCIGTAGATGATGGGGTT 3 ' T C AGG A A AC CA A GC PRIMER PAIR 2: 5' AACTACTICTGGITGCTGGTGGAGGGCCTCTA 3' C A GG G T 5 ' GAAGCAGTAIATAATGGCAACAAAAAAGCCCTGGAA 3' A G CA G GA C T In an alternative method, the inorganic-ion receptor can be cloned by uεe of a monoclonal antibody generated against the receptor. Monoclonal antibodies provide powerful tools for the immunoaffinity purification of specific proteins. Once purified, limited amino acid sequence data can be obtained from the protein of interest, and used to deεign oligonucleotide sequence probeε to screen for clones of the complete cDNA sequence. An example involving a calcium receptor will be described. For production of hybridomas, whole bovine parathyroid gland cellε are uεed aε the immunogen. Purified, diεpersed cells are obtained, and live or fixed cell preparations are injected intraperitoneally into the appropriate mouse strain, according to established procedures. Standard protocols are followed for immunization schedules and for the production of hybridomas. A two-step screening procedure is used to identify hybridomas secreting monoclonal antibodies that recognize the Ca 2+ receptor. The initial screen will identify those monoclonals that recognize parathyroid cell surface antigens. Immunohistochemical techniqueε are then used to screen hybridoma supernatants for the presence of mouεe antibodies that bind to the surface of parathyroid cells. This screen can be performed on fixed sections of parathyroid gland tissue, or on disperεed cells in primary culture. The techni ueε for thiε aεεay are well eεtabliεhed in the literature. This screen will identify hybridomas producing monoclonal antibodieε to a variety of cell-surface 2+ determinantε, and monoclonalε εpecific for the Ca receptor would be expected to comprise only a small subset of these. To identify monoclonal antibodies that bind to the Ca 2+ receptor, hybπdoma εupernatantε that test positive in the initial screen are assayed for their ability to block the response of cultured parathyroid cells to Ca 2+ receptor agonists. Some antibodies that bind to the extracellular domain of the receptor are expected to inhibit or activate ligand binding or to otherwise interfere with or affect receptor activation. Monoclonal antibodieε positive in both screens are characterized through Western blotting, immunoprecipitation and immunohistochemistry. This permits the determination of the size of the antigen that is recognized and its tisεue distribution. The appropriate monoclonal antibody is then used for purification of the Ca 2+ receptor protein by immunoaffinity chromatography, following standard techniques. Sufficient quantities of protein are obtained to allow limited amino acid sequence determination. Degenerate oligonucleotide probes are then designed on the basis of the peptide sequence information. These probes are then used to screen parathyroid gland cDNA libraries for full-length clones of the Ca 2+ receptor. Clones obtained are characterized by DNA sequencing and by functional expresεion in the oocyte εystem and in cultured mammalian cell lines. Alternatively, the antibodies can be used to screen expresεion libraries, e.g. , cDNA librarieε in λgtll or itε equivalent, to determine thoεe cloneε expreεεing antigenically reactive protein. Such cloneε can then be εequenced to determine whether they encode a protein that might be a Ca 2+ receptor. It will also be appreciated by those skilled in the art that phage display libraries can be used to clone and analyze calcium receptorε in place of monoclonal antibodieε. In these libraries, antibody-variable regions or random peptideε are shotgun cloned into phage expresεion vectorε εuch that the antibody regions or peptides are displayed on the surface of the phage particle. Phage(s) which diεplay antibody regions or peptides capable of high specific binding to calcium receptors will bind to cells which display these receptors (e.g. , parathyroid cells, C-cells, osteoclaεtε, etc.). Hundredε of millions of such phage can be panned against theεe cell typeε preferentially εelecting those phage which can bind to these cells (which includeε those phage binding to calcium receptors). In this manner, the complexity of the library can be vastly reduced. Iterative repetition of this process resultε in a pool of phage which bind to the cell type used. Subsequently, the screens described above for monoclonal antibodies can be used to iεolate phage which display- calcium receptor-binding antibody or peptide regions, and these phage can be used to isolate the calcium receptor for purpoεeε of εtructural identification and cloning. Kitε to prepare εuch phage- diεplay librarieε are commercially available (e.g., Stratacyte, or Cambridge Antibody Technology Limited) . Recombinant phage endowed with εuch calcium receptor-binding properties can also be used in lieu of monoclonal antibodies in the various analyses of calcium receptors. Such phage can also be used in high throughput binding-competition screenε to identify organic compoundε capable of functional binding to calcium receptors which can serve aε εtructural leadε for the development of human therapeutics acting at the calcium receptor. In another alternative, affinity cross-linking of radioligands to their receptors can be used to isolate the receptor protein as described by Pilch & Czech, 1 Receptor Biochem. Methodol. 161, 1984. Covalent attachment of a radioligand allows extensive washing to remove non-specific binding. For example, a high- affinity molecule, e.g. , a random copolymer of arginine and tyrosine (MW = 22K; argtyr ratio = 4:1) which mobilizes mtracellular Ca 2+ with an EC cn of about 100 nM or lesε, is iodinated with 125I, and 5 c°roεε-lmked. Protammeε, because of their much smaller size, may be preferable in cross-linking studieε and can be reductively alkylated aε deεcribed by Dottavio-Martin & Ravel, 87 Analyt. Biochem. 562, 1978. Nonεpecific labelling iε kept to a minimum by croεε-linking in the preεence of unlabeled polycationε and di- and trivalent cationε. At high concentrationε of these moleculeε nonεpecific interactionε of the label with the cell εurface might be reduced. The invention provideε iεolated nucleic acid sequences encoding inorganic-ion receptors and the isolated receptors themselves. It also provides unique fragments of the foregoing. The term "isolated" refers to a nucleic acid sequence: (i) amplified in vitro by, for example, polymerase chain reaction (PCR); (ii) syntheεized by, for example, chemical synthesis; (iii) recombinantly produced by cloning; or (iv) purified, as by cleavage and gel separation. The term "isolated" when used in descriptionε of polypeptide or amino acid εequences refers to polypeptides resulting from an expression system using the isolated nucleic acid sequences of the invention, as well aε polypeptideε syntheεized by, for example, chemical εynthetic methodε, and polypeptideε εeparated from native biological materialε, and then substantially purified using conventional protein analytical procedures. Also included within the scope of the invention are unique fragments of inorganic-ion receptors. The term unique fragments refers to portions of the receptor that find no counterpart in known sequenceε as of the date of this invention. These polypeptide fragments can be readily identified aε unique by scanning protein databases known as of the time of the invention for identical peptides. In addition to generating fragments of receptors from expresεion of cloned partial εequenceε of receptor DNA, fragmentε can be generated directly from the intact protein. Proteinε are specifically cleaved by proteolytic enzymes, including, but not limited to, trypsin, chymotrypsin or pepεin. Each of theεe enzymeε is specific for the type of peptide bond it attacks. Trypsin catalyzes the hydrolysiε of peptide. bondε whoεe carbonyl group iε from a baεic amino acid, usually arginine or lysine. Pepsin and chymotrypsin catalyze the hydrolysis of peptide bonds from aromatic amino acids, particularly tryptophan, tyrosine and phenylalanine. Alternate εets of cleaved polypeptide fragments are generated by preventing cleavage at a site which is suεceptible to a proteolytic enzyme. For example, reaction of the ε-amino groupε of lyεine with ethyltrifluorothioacetate in mildly baεic εolution yieldε a blocked amino acid reεidue whoεe adjacent peptide bond is no longer suεceptible to hydrolyεiε by trypεin. Goldberger et al. Biochem. , 1:401 (1962). Treatment of such a polypeptide with trypsin thus cleaves only at the arginyl residues. Polypeptides also can be modified to create peptide linkages that are susceptible to proteolytic enzyme catalyzed hydrolysiε. For example, alkylation of cyεteine residues with β-haloethylamines yields peptide linkages that are hydrolyzed by trypεin. Lindley, Nature, 178: 647 (1956). In addition, chemical reagents that cleave polypeptide chains at specific residues can be used. Witcop, Adv. Protein Chem. 16: 221 (1961). For example, cyanogen bromide cleaves polypeptides at methionine residues. Gross & Witkip, J. Am Chem Soc. , 83: 1510 (1961). Thus, by treating an inorganic ion receptor, such as, for example, a human calcium receptor or fragments thereof, with various combinations of modifiers, proteolytic enzymes and/or chemical reagents, numerous discrete overlapping peptides of varying sizes are generated. These peptide fragments can be isolated and purified from such digeεtε by chromatographic methodε. Alternatively, fragmentε can be εynthesized using an appropriate solid state synthetic procedure. Steward and Young, Solid Phase Peptide Syntheεis, Free antle, San Fansisco, CA (1968). The fragmentε may be uεed in aεεays, as ion-binding agents, in the production of antibodies and the like. The fragments also may be selected to have desirable biological activitieε. For example, the fragment may include juεt the binding site, or a site which binds to agonists or antagonistε (e.g. of calcium), as described herein. Such fragments are readily identified by those of ordinary skill in the art using routine methods to detect εpecific binding to the fragment. For example, in the case of a calcium receptor, a fragment to be tested can be expressed, using recombinant DNA methodology, from a fragment of the gene encoding the recombinant receptor. This fragment is then contacted with calcium or another chemical under appropriate association conditions to determine whether the calcium binds to the fragment. These fragmentε are useful in screening asεayε for agonistε and antagonists of calcium, and for therapeutic effect where it is useful to remove calcium from serum, or other bodily tissues. Other useful fragments include thoεe that have only the external portion, membrane-spanning portion, or mtracellular portion of the receptor. These portions are readily identified by comparison of the amino acid sequence of the receptor with those of known receptors, or by other standard methodology. These fragments are useful for forming chimeric receptorε with fragments of other receptors so that a cell lacking a receptor may be formed with an mtracellular portion which performs a desired function within that cell, and an extracellular portion which causeε that cell to reεpond to the preεence of ionε, or those agonists or antagonists described herein. Such chimeric receptor genes when appropriately formulated are useful genetic therapies for a variety of diseases involving dysfunction of receptors or where modulation of receptor function provides a desirable effect in the patient. In addition, chimeric receptors can be constructed such that the mtracellular domain is coupled to a desired enzymatic process which can be readily detected by colorometric, radiometric luminometric, spectrophotometric or fluorometric assays and is activated by interaction of the extracellular portion with its native ligand (e.g. calcium) or agonists and or antagonists of the invention. Cells expressing such chimeric receptors are the basis for facilitated screens for the discovery of new agonists and/or antagonists of the invention. The invention also features muteins or analogs and other derivatives of isolated receptors, as described herein. Thuε, the invention embraceε not only naturally occurring proteinε, but also εuch derivativeε. Such derivativeε have the desired receptor activity described herein and are generally identified by methods described herein. While examples of such proteins, and genes encoding them, are provided, these examples are not limiting in the invention but demonstrate only the variation that can be associated with such genes and proteins. Generally, the gene will have the amino acid sequence of the native receptor, but may be altered at one or more amino acid positionε which do not significantly affect the receptor activity of the produced receptor protein. Thuε, for example, in non-conεerved regionε of the calcium receptor protein (i.e. , thoεe regionε not necessary for receptor activity) amino acids may be deleted, added or substituted. In more conserved regions, which are required for receptor activity, amino acids may be more conservatively substituted. For example, one or more amino acid residues within the sequence can be substituted by another amino acid of a similar polarity which acts as a functional equivalent. Substitutes for an amino acid within the sequence may be selected from other members of the clasε to which the amino acid belongε. The non-polar (hydrophobic) amino acidε include alanine, leucine, iεoleucine, valine, proline, phenylalanine, tryptophan and methionine. The polar neutral amino acidε include glycine, serine, threonine, cysteine, tyrosine, asparagine, and glutamine. The positively charged (basic) amino acids include arginine, lysine and histidine. The negatively charged (acidic) amino acids include aεparatic acid and glutamic acid. Thoεe of ordinary skill in the art will recognize that εtandard procedures can be used to determine the conserved and non-conserved regions of the protein using in vitro mutagenesis techniques or deletion analyses, and that all such derivatives are equivalent of those described below. Also included within the scope of the invention are receptor proteins or unique fragments or derivatives thereof which are differentially modified during or after translation, e.g., by phosphorylation, glycosylation, croεεlinking, acylation, proteolytic cleavage, linkage to an antibody molecule, membrane molecule or other ligand, (Ferguεon et al ■ , 1988, Ann. Rev. Biochem. 57:285-320) . In addition, recombinant nucleic acid εequences of the invention may be engineered so as to modify proceεεing or expression of receptor sequenceε. For example, and not by way of limitation, the coding sequence may be combined with a promoter sequence and/or a ribosome binding εite using well characterized methods, and thereby facilitate improve expression and bioavailability. Additionallyi a given recombinant coding sequence can be mutated m vitro or m vivo, to create variations in coding regions and/or form new restriction endonuclease sites or destroy preexisting ones, to facilitate further in vitro modification. Any technique for mutageneεis known in the art can be used including, but not limited to, m vitro site-directed mutagenesiε (Hutchinεon, et al. , 1978, J. Biol. Chem. 253:6551), uεe of TAB® linkerε (Pharmacia), PCR-directed mutageneεiε, and the like. In addition, codonε may be modified εuch that while they encode an identical amino acid, that codon may be a preferred codon in the choεen expreεsion system. The invention also provides unique fragments of nucleic acid encoding an inorganic-ion receptor. The term "unique fragments" refers to portions of the nucleic acid that find no identical counterpart in known sequences as of the date of this invention. These fragments can be identified easily by an analysiε of nucleic acid data bases existing as of the date of the invention to detect counterparts. Unique fragments are useful inter alia in cloning procedures and asεayε. The invention further provideε receptor binding agentε including antibodies and/or fragments thereof which can be conjugated to a toxin moiety, or expressed along with a toxin moiety as a recombinant fusion protein. The toxin moiety will bind to and enter a target cell using interaction of the binding agent and the corresponding target cell surface receptor. The toxic moiety to which the agent, antibody and/or fragment is conjugated can be a protein such as, for example, pokeweed anti-viral protein, ricin, gelonin, abrin, diphtheria exotoxin, or Pseudomonaε - I l l - exotoxin. The toxin moiety can also be a high energy-emitting radionuclide such as cobalt-60. The chemical structure of the toxin moiety is not intended to limit the scope of the invention in any way. Those of ordinary skill in the art will recognize that a large variety of posεible moieties can be linked to the binding agents. See, for example, "Conjugate Vaccines", Contributions to Microbiology and Immunology, J.M. Cruse and R.E. Lewis, Jr (edε) . Carger Preεε, New York, (1989). It further iε art recognized that many toxin moieties, including those specifically listed above, are considered pharmaceutically acceptable. The conjugation of the binding agent to another moiety (e.g. bacterial toxin) can be accomplished by any chemical reaction that will bind the two molecules so long as both molecules retain their respective activity. This linkage can include many chemical mechanismε, for instance covalent binding, affinity binding, intercalation, coordinate binding and complexation. The preferred binding is, however, covalent binding. The covalent binding can be achieved either by direct condensation of existing εide chainε or by the incorporation of external bridging moleculeε. Many bivalent or polyvalent linking agentε are uεeful in coupling protein moleculeε, εuch as an antibody, to other molecules. For example, representative coupling agents can include organic compounds such as thioeεterε, carbodiimideε, εuccinimide eεters, diisocyanateε, glutaraldehydeε, diazobenzeneε and hexamethylene diamineε. Thiε liεting iε not intended to be exhauεtive of the variouε claεεeε of coupling agentε known in the art but, rather, is exemplary of the more common coupling agents. (See Killen and Lindstro 1984, "Specific killing of lymphocytes that cause experimental Autoimmune Myasthenia Gravis by toxin-acetylcholine receptor conjugates." Jour. Immun. 133:1335-2549; Jansen, F.K., H.E. Blythman, D. Carriere, P. Caεella, 0. Groε, P. Groε, J.C. Laurent, F. Paolucci, B. Pau, P. Poncelet, G. Richer, H. Vidal, and G.A. Voisin. 1982. "Immunotoxinε: Hybrid moleculeε combining high specificity and potent cytotoxicity". Immunological Reviews 62:185-216; and Vitetta et al., supra) ■ Using recombinant DNA techniques, the preεent invention provideε for target cellε including mammalian target cells which are engineered to expreεε inorganic-ion receptors. For example, the geneε for εuch receptorε, cloned according to the methods set forth above, may be inserted into cells which naturally expresε the receptorε εuch that the recombinant gene iε expreεεed at much higher levelε. The present invention also provides for experimental model systemε for studying the physiological role of the receptors. In these model syεtemε, the inorganic-ion receptors, fragments, or derivatives thereof, may be either supplied to the system or produced within the system. Such model syεtemε could be uεed to εtudy the effectε or cell function of receptor exceεε or depletion. The experimental model systemε may be used to study the effects in cell or tisεue cultureε, in whole animals, or in particular cells or tissues within whole animals or tisεue culture εyεtems, or over specified time intervals (including during embryogenesiε) . A preferred embodiment iε aεεayε involving the cloned receptorε or parts thereof, including particularly those useful in high through-put drug screening asεayε. In additional embodimentε of the invention, a recombinant gene may be used to inactivate the endogenous gene by homologous recombination, and thereby create an inorganic-ion receptor deficient cell, tisεue, or animal. For example, and not by way of limitation, a recombinant gene may be engineered to contain an inεertional mutation (e.g.. the neo gene) which, when inεerted into the genome of a recipient cell, tissue or animal, inactivates tranεcription of the receptor. Such a construct may be introduced into a cell, such as an embryonic stem cell, by a technique such as transfection, transduction, injection, etc. Stem cellε lacking an intact receptor εequence may generate tranεgenic animalε deficient in the receptor. A "tranεgenic animal" is an animal having cells that contain DNA which has been artificially inserted into a cell, which DNA becomes part of the genome of the animal which develops from that cell. Preferred transgenic animalε are primateε, mice, ratε, cows, pigε, horεeε, goatε, εheep, dogs and cats. The transgenic DNA may encode for human inorganic-ion receptors. In a further embodiment of the invention, native expression in an animal may be reduced by providing an amount of anti-sense RNA or DNA effective to reduce expresεion of the receptor. A variety of methodε are available for the production of transgenic animals associated with this invention. DNA can be injected into the pronucleus of a fertilized egg before fusion of the male and female pronuclei, or injected into the nucleus of an embryonic cell (e.g., the nucleus of a two-cell embryo) following the initiation of cell division (Brinster et a_l. , Proc. Nat. Acad. Sci. USA, 82: 4438-4442 (1985)). Embryos can be infected with viruses, especially retroviruses, modified to carry inorganic-ion receptor nucleotide sequenceε of the invention. Pluripotent stem cells derived from the inner cell masε of the embryo and εtabilized in culture can be manipulated in culture to incorporate nucleotide sequences of the invention. A transgenic animal can be produced from such cells through implantation into a blastocyεt that iε implanted into a foster mother and allowed to come to term. Animals suitable for transgenic experiments can be obtained from standard commercial sourceε εuch aε Charleε River (Wilmington, MA), Taconic (Germantown, NY), Harlan Sprague Dawley (Indianapoliε, IN), etc. The procedureε for manipulation of the rodent embryo and for microinjection of DNA into the pronucleuε of the zygote are well known to thoεe of ordinary skill in the art (Hogan et §JL., supra) . Microinjection procedures for fish, amphibian eggs and birds are detailed in Houdebine and Chourrout, Experientia, 47: 897-905 (1991). Other procedures for introduction of DNA into tisεueε of animalε are deεcribed in U.S. Patent No., 4,945,050 (Sandford et al. , July 30, 1990). By way of example only, to prepare a tranεgenic mouεe, female mice are induced to εuperovulate. Females are placed with males, and the mated females are sacrificed by CO, asphyxiation or cervical dislocation and embryos are recovered from excised oviducts. Surrounding cumulus cells are removed. Pronuclear embryoε are then waεhed and εtored until the time of injection. Randomly cycling adult female mice are paired with vasectomized maleε. Recipient femaleε are mated at the εame time as donor femaleε. Embryoε then are transferred surgically. The procedure for generating transgenic rats is similar to that of mice. See Hammer et al.. , Cell, 63:1099-1112 (1990). Methods for the culturing of embryonic stem (ES) cellε and the subsequent production of transgenic animalε by the introduction of DNA into ES cellε uεing methodε εuch aε electroporation, calcium phosphate/DNA precipitation and direct injection also are well known to those of ordinary skill in the art. See, for example, Teratocarcinomas and Embryonic Stem Cellε, A Practical Approach, E.J. Robertson, ed. , IRL Presε (1987) . In caεes involving random gene integration, a clone containing the sequence(s) of the invention iε co-transfected with a gene encoding resiεtance. Alternatively, the gene encoding neomycin reεistance is phyεically linked to the sequence(s) of the invention. Transfection and isolation of desired clones are carried out by any one of several methods well known to those of ordinary skill in the art (E.J. Robertson, supra) . DNA moleculeε introduced into ES cellε can also be integrated into the chromosome through the procesε of homologous recombination. Capecchi, Science, 244: 1288-1292 (1989). Methods for positive εelection of the recombination event (i.e., neo reεistance) and dual poεitive-negative selection (i.e., neo resistance and gancyclovir resistance) and the subsequent identification of the desired clones by PCR have been described by Capecchi, supra and Joyner et al ■ , Nature, 338: 153-156 (1989), the teachings of which are incorporated herein. The final phase of the procedure is to inject targeted ES cells into blastocyεtε and to transfer the blastocyεts into pseudopregnant females. The resulting chimeric animals are bred and the offspring are analyzed by Southern blotting to identify individuals that carry the transgene. Procedures for the production of non-rodent mammals and other animals have been discuεεed by others. See Houdebine and Chourrout, supra; Pursel et al., Science 244: 1281-1288 (1989); and Simms et _______ . , Bio/Technology, 6: 179-183 (1988) . Useε Primary hyperparathyroidiεm (HPT) is characterized by hypercalcemia and elevated levels of circulating PTH. One of the major defects in HPT appears to be a diminished senεitivity of parathyroid cellε to negative feedback regulation by extracellular Ca 2+. Thus, in tisεue from patients with primary HPT, the "set-point" for extracellular Ca 2+ is shifted to the right so that higher than normal concentrations of extracellular Ca 2+ are required to depresε PTH εecretion. Moreover, in primary HPT, even high concentrationε of extracellular Ca 2+ often depress PTH secretion only partially. In secondary (uremic) HPT, a similar increase in the set-point for extracellular Ca 2+ is observed even though the degree to which Ca 2+ suppresεes PTH secretion is normal . The changes in PTH secretion are paralleled by changes in [Ca 2+].: the εet-point for extracellular Ca2+-i.nduced increases in [Ca 2+]. is shifted to the right and the magnitude of such increases is reduced. Moreover, staining of tisεue with a monoclonal antibody that appearε to recognize the Ca 2+ receptor is diminished in adenomatous and hyperplastic parathyroid cells. The Ca 2+ receptor constituteε a diεcrete molecular entity for pharmacological intervention. Moleculeε that mimic or antagonize the action of extracellular Ca 2+ are beneficial in the long-term management of both primary and εecondary HPT. Such moleculeε provide the added impetuε required to εuppress PTH secretion which the hypercalcemic condition alone cannot achieve. Such molecules with greater efficacy than extracellular Ca 2+ may overcome the apparent nonsuppreεεible component of PTH secretion which is particularly troublesome in adenomatous tisεue. Alternatively or additionally, εuch molecules can depresε εyntheεiε of PTH, aε prolonged hypercalcemia has been shown to depresε the levelε of preproPTH mRNA in bovine and human adenomatouε parathyroid tiεεue. Prolonged hypercalcemia alεo depreεses parathyroid cell proliferation in vitro, so calcimimetics can also be effective in limiting the parathyroid cell hyperplasia characteristic of secondary HPT. Other cells in the body can respond directly to physiological changes in the concentration of extracellular Ca 2+. Calciton secretion from parafollicular cells in the thyroid (C-cells) is regulated by changes in the concentration of extracellular Ca 2+. Renin secretion from juxtaglomerular cells in the kidney, like PTH εecretion, is depressed by increased concentrations of extracellular Ca 2+. Extracellular Ca2+ causes the mobilization of intracellular Ca 2+ in these cells. Other kidney cells respond to calcium as follows: elevated Ca 2+ inhibits formation of l,25(OH) 2 Vitamin D by proximal tubular cells, stimulates production of calcium-binding protein in distal tubular cells, and inhibits tubular reabsorption of Ca 2+ and Mg2+ and the action of vasopreεεm on the medullary thick aεcending limb of Henle'ε loop (MTAL), reduceε vaεopressin action in the cortical collecting duct cells, and affects vascular εmooth muεcle cellε in blood vesselε of the renal glomeruluε. Calcium promoteε the differentiation of inteεtinal goblet cellε, mammary cellε, and εkin cellε. It also inhibits atrial natriuretic peptide secretion from cardiac atria, reduces cAMP accumulation in platelets, alters gastrin and glucagon εecretion, and acts on vascular smooth muscle cells to modify cell secretion of vasoactive factorε. Isolated osteoclaεtε reεpond to increases in the concentration of extracellular Ca 2+ with correεponding increaεeε in [Ca 2+]. that ariεe partly from the mobilization of mtracellular Ca 2+. Increaεes in [Ca 2+]. in osteoclaεtε are aεsociated with an inhibition of functional responεeε (bone reεorption) analogouε to PTH secretion in parathyroid cells. Releaεe of alkaline phoεphataεe from bone-forming oεteoblaεtε is directly stimulated by calcium. Thus, there are sufficient indications to suggest that Ca 2+, in addition to its ubiquitous role as an intracellular signal, also functions as an extracellular εignal to regulate the reεponεeε of certain specialized cells. Molecules of this invention can be uεed in the treatment of diεeaεeε aεεociated with diεrupted Ca 2+ reεponses in theεe cellε. Cloning the Ca 2+ receptor on parathyroid cellε and other cellε will allow the preεence of homologouε proteinε in other cells to be directly asεessed. A family of structurally homologous Ca 2+ receptor proteins can thus be obtained. Such receptors will allow underεtanding of how theεe cellε detect extracellular Ca 2+ and enable evaluation of the mechaniεm(s) as a εite of action for the therapeutics described herein effective in the treatment of HPT, osteoporosis, and hypertension, and novel therapies for other bone and mineral-related diseaεeε. Other uεes are discuεεed above. For example, recombinant Ca 2+ receptor proteinε may be uεed in therapy, and introduced by εtandard methodε, e.g. , by tranεfection of nucleic acid encoding that protein. In addition, such protein is useful in assays for calcimimetic molecules of this invention. The following examples illustrate the invention but do not limit its scope. Methods for the culturing of embryonic εtem (ES) cellε and the subsequent production of tranεgenic animalε by the introduction of DNA into ES cells using methods such as electroporation, calcium phosphate/DNA precipitation and direct injection alεo are well known to thoεe of ordinary skill in the art. See, for example, Teratocarcinomas and Embryonic Stem Cells, A Practical Approach, E.J. Robertson, ed. , IRL Presε (1987) . In cases involving random gene integration, a clone containing the sequence(ε) of the invention iε co-transfected with a gene encoding resistance. Alternatively, the gene encoding neomycin resistance is physically linked to the sequence(s) of the invention. Transfection and isolation of desired clones are carried out by any one of several methods well known to those of ordinary skill in the art (E.J. Robertson, supra) ■ DNA molecules introduced into ES cells can also be integrated into the chromosome through the procesε of homologouε recombination. Capecchi, Science, 244: 1288-1292 (1989). Methodε for positive selection of the recombination event (i.e. , neo reεiεtance) and dual poεitive-negative εelection (i.e. , neo reεistance and gancyclovir resiεtance) and the subsequent identification of the desired clones by PCR have been deεcribed by Capecchi, εupra and Joyner et al . , Nature, 338: 153-156 (1989), the teachingε of which are incorporated herein. The final phaεe of the procedure iε to inject targeted ES cellε into blaεtocysts and to transfer the blastocyεtε into pεeudopregnant femaleε. The reεulting chimeric animals are bred and the offspring are analyzed by Southern blotting to identify individuals that carry the transgene. Procedureε for the production of non-rodent mammalε and other animalε have been diεcuεεed by otherε. See Houdebine and Chourrout, supra; Pursel et al. , Science 244: 1281-1288 (1989); and Simmε et al., Bio/Technology, 6: 179-183 (1988) . Uses Primary hyperparathyroidism (HPT) is characterized by hypercalcemia and elevated levels of circulating PTH. One of the major defects in HPT appearε to be a diminished sensitivity of parathyroid cells to negative feedback regulation by extracellular Ca 2+. Thus, in tissue from patients with primary HPT, the "set-point" for extracellular Ca 2+ is shifted to the right so that higher than normal concentrations of extracellular Ca 2+ are required to depreεε PTH secretion. Moreover, in primary HPT, even high concentrations of extracellular Ca 2+ often depresε PTH secretion only partially. In secondary (uremic) HPT, a similar increase in the set-point for extracellular Ca 2+ is observed even though the degree to which Ca 2+ suppreεses PTH secretion is normal . The changes in PTH secretion are paralleled by changes in [Ca 2+].: the set-point for extracellular Ca 2+-induced increaseε 1 in [Ca 2+]. is shifted to the right and the magnitude of such increaεeε iε reduced. Moreover, staining of tissue with a monoclonal antibody that appears to recognize the Ca 2+ receptor i.s dimi•ni•shed in adenomatous and hyperplastic parathyroid cells. The Ca 2+ receptor constituteε a diεcrete molecular entity for pharmacological intervention. Moleculeε that mimic or antagonize the action of extracellular Ca 2+ are beneficial in the long-term management of both primary and εecondary HPT. Such moleculeε provide the added impetuε required to εuppreεε PTH εecretion which the hypercalcemic condition alone cannot achieve. Such moleculeε with greater efficacy than extracellular Ca 2+ may overcome the apparent nonεuppreεεible component of PTH secretion which is particularly troublesome in adenomatous tissue. Alternatively or additionally, such moleculeε can depress synthesis of PTH, as prolonged hypercalcemia has been shown to depress the levels of preproPTH mRNA in bovine and human adenomatous parathyroid tissue. Prolonged hypercalcemia also depresses parathyroid cell proliferation in vitro, so calcimimetics can also be effective in limiting the parathyroid cell hyperplasia characteristic of secondary HPT, Other cells in the body can respond directly to physiological changes in the concentration of extracellular Ca 2+. Calcitonm secretion from parafollicular cells in the thyroid (C-cells) is regulated by changeε in the concentration of extracellular Ca 2+. Renm εecretion from juxtaglomerular cellε in the kidney, like PTH secretion, is depresεed by increaεed concentrationε of extracellular Ca 2+. Extracellular Ca2+ causes the mobilization of intracellular Ca 2+ m. these cellε. Other kidney cellε reεpond to calcium aε followε: elevated Ca 2+ inhibitε formation of l,25(OH) 2 Vitamin D by proximal tubular cellε, stimulates production of calcium-binding protein in distal tubular cells, and inhibits tubular reabsorption of Ca 2+ and Mg2+ and the action of vasopreεεin on the medullary thick aεcending limb of Henle'ε loop (MTAL), reduceε vaεopreεεin action in the cortical collecting duct cellε, and affectε vaεcular εmooth muεcle cells in blood vesεelε of the renal glomerulus. Calcium promotes the differentiation of intestinal goblet cellε, mammary cellε, and εkin cells. It alεo inhibitε atrial natriuretic peptide εecretion from cardiac atria, reduceε cAMP accumulation in plateletε, alters gastrin and glucagon secretion, and acts on vaεcular smooth muscle cells to modify cell secretion of vasoactive factors. Isolated osteoclaεtε reεpond to increases in the concentration of extracellular Ca2+ with correεponding increaεeε in [Ca 2+]. that ariεe partly from the mobilization of mtracellular Ca 2+. Increaεeε in [Ca 2+]. in osteoclasts are asεociated with an inhibition of functional reεponses (bone reεorption) analogouε to PTH εecretion in parathyroid cellε. Releaεe of alkaline phoεphatase from bone-forming osteoblastε is directly stimulated by calcium. Thus, there are sufficient indicationε to εuggest that Ca 2+, in addition to its ubiquitous role as an intracellular εignal, also functions as an extracellular signal to regulate the responεeε of certain εpecialized cellε. Moleculeε of thiε invention can be uεed in the treatment of diseaseε aεεociated with diεrupted Ca 2+ reεponεeε in theεe cellε. Cloning the Ca 2+ receptor on parathyroid cellε and other cells will allow the presence of homologous proteins in other cells to be directly asεessed. A family of structurally homologous Ca 2+ receptor proteins can thuε be obtained. Such receptors will allow understanding of how theεe cellε detect extracellular Ca 2+ and enable evaluation of the mechaniεm(ε) aε a site of action for the therapeutics deεcribed herein effective in the treatment of HPT, osteoporosiε, and hypertenεion, and novel therapieε for other bone and mineral-related diεeaεeε. Other uεeε are diεcuεεed above. For example, recombinant Ca 2+ receptor proteinε may be uεed in therapy, and introduced by εtandard methodε, e.g. , by tranεfection of nucleic acid encoding that protein. In addition, εuch protein iε uεeful in aεεayε for calcimimetic moleculeε of thiε invention. The following examples illustrate the invention but do not limit its εcope. Examples In the studies described herein, a variety of organic moleculeε were found to mobilize intracellular Ca 2+ and depreεε PTH εecretion in parathyroid cells. These molecules are structurally diverse but most have a net positive charge at physiological pH. The cationic nature of the organic moleculeε plays an important role but is not the sole factor determining activity. Example 1: Screening Calcimimetic Molecules on Bovine Parathyroid cells Disεociated bovine parathyroid cellε were purified on gradientε of Percoll and cultured overnight in εerum- free medium. The cellε were subsequently loaded with fura-2 and the concentration of free intracellular Ca 2+ meaεured fluorimetricly. Changeε in [Ca 2+]. were used to screen for molecules active at the Ca 2+ receptor. To be considered a calcimimetic, a molecule was required to show the normal effects caused by increaεing extracellular Ca 2+ and triggered by the activation of the Ca2+ receptor. That is, 1) The molecule must elicit an increaεe in [Ca 2+].; the increaεe in [Ca2+]. may perεiεt in the absence of extracellular Ca 2+ and/or the molecule may potentiate increaseε in [Ca 2+]. elicited by extracellular Ca 2+ 2) The molecule muεt cauεe a decreaεe in isoproterenol-stimulated cyclic AMP formation which is blocked by pertussiε toxin; 3) The molecule must inhibit PTH secretion over the same range of concentrations that cause the increase in [Ca 2+].; and 4) The concentration-response curves for increaεeε in [Ca 2+]. and PTH εecretion by the molecule muεt be shifted to the right by a PKC activator, such as phorbol myristate acetate (PMA) . Several structurally different classes of molecules were tested: polyamines, aminoglycoεide antibioticε, protamine, and polymerε of lysine or arginine. The structures of these molecules are depicted in Figure 1. Included in Figure 1 are the net poεitive charge of the molecules and their EC-- 's for evoking the mobilization of mtracellular Ca 2+ i.n bovi.ne parathyroid cells. In general, the greater the net positive charge on the molecule, the greater its potency in causing the mobilization of mtracellular Ca 2+. However, some striking exceptions to thiε apparent rule have been found aε diεcuεεed below. Aε can be εeen from the figureε, spermine, neomycin B, and protamine evoked rapid and transient increaεeε in [Ca 2+]. in fura-2-loaded bovine parathyroid cellε (Figε. 6, 7, 11). They did not, however, cause sustained, εteady-εtate increaεeε in [Ca 2+] . in bovine parathyroid cellε (Fig. 6, 11), although they did in human parathyroid cellε (Fig. 19). In thiε reεpect, they resembled the cytosolic Ca 2+ reεponεe elicited by extracellular Mg 2+, which causes the mobilization of tracellular Ca 2+ unaccompanied by an influx of extracellular Ca 2+ m bovine cells (Fig. lib). Transient increases in [Ca2+]. elicited by spermine, neomycin B, or protamine were not blocked by low concentrations (1 μM) of La 3+ or Gd 3+ (Fig. llf,g). Cytosolic Ca 2+ transientε elicited by the molecular polycations persisted in the absence of extracellular Ca 2+ but were blocked when cellular stores of Ca 2+ were depleted by pretreatment with ionomycin (Figs. 7; llh,i). All these molecules therefore cause the mobilization of intracellular Ca 2+ in parathyroid cells. It was additionally shown that the molecular polycationε mobilized the same pool of mtracellular Ca 2+ aε that uεed by extracellular Ca 2+. Thuε, increaεing the concentration of extracellular Ca 2+ progressively inhibited the transient increases in [Ca 2+]. evoked by εpermine (Fig. 6). Conversely, a maximally effective concentration of spermine or neomycin B (Fig. 12) blocked transient, but not steady-state increaseε in [Ca 2+]. evoked by extracellular Ca 2+ x Significantly, spermine, neomycin B, and protamine inhibited PTH secretion to the same extent as extracellular Ca 2+. These inhibitory effects on secretion were obtained at concentrations that caused the mobilization of intracellular Ca 2+ (Figs. 8, 13). These findings are relevant to understanding the mechanisms contributing to the regulation of PTH secretion by extracellular Ca 2+. Because a variety of inorganic polycations all inhibit secretion, yet only extracellular Ca 2+ causeε εuεtained, 2+ steady-state increaεeε in [Ca ]., such increaseε in [Ca 2+]. cannot be importantly involved in the regulation of εecretion. Mobili •zation of mtracellular Ca2+, rather than the influx of extracellular Ca2+, lε the essential mechanism asεociated with the inhibition of PTH εecretion. This is important becauεe it defineε the εufficient mechaniεm to be affected if a molecule iε to affect PTH secretion; molecules stimulating selectively the influx of extracellular Ca 2+ wi.ll be relati.vely i.neffecti.ve m. suppreεεing PTH secretion. In contrast, molecules causing εolely the mobilization of mtracellular Ca 2+ εhould be juεt aε efficaciouε as extracellular Ca 2+ m. suppressing PTH secretion. Like the mobilization of tracellular Ca 2+ elicited by extracellular Ca 2+, that elicited by molecular polycations was depressed by PMA. A representative experiment εhowing the preferential inhibitory effects of PMA on cytosolic Ca 2+ tranεientε elicited by εpermine is εhown in Fig. 14. Cytosolic Ca 2+ transientε evoked by ATP were unaffected, even when a εubmaximal concentration of ATP waε uεed. The effect of PMA on cytoεolic Ca 2+ tranεients elicited by the molecular polycations paralleled itε effect on reεponεeε to extracellular Ca 2+; in both caεeε there waε a εhift to the right in the concentration-reεponse curve (Fig. 15). The depresεive effectε of PMA on [Ca 2+]. were accompanied by potentiating effectε on εecretion which were overcome at higher concentrationε of the organic polycationε (Fig. 16). The mobilization of tracellular Ca 2+ elicited by molecular polycationε waε aεεociated with increaεeε in the formation of inoεitol phoεphateε. For example, protamine cauεed a rapid (within 30 s) increase in the formation of IP 3 which was accompanied by a rise in levelε of IP.. Both these effects were dependent on the concentration, of extracellular protamine (Fig. 17). Moreover, pretreatment with PMA blunted the formation of inositol phoεphateε elicited by molecular polycations. Representative results obtained with εpermine are presented in Fig. 18. Spermine, neomycin B, and protamine depresεed iεoproterenol-induced increaεes in cyclic AMP. Like the inhibitory effects of extracellular Ca 2+ on cyclic AMP formation, those caused by molecular polycations were blocked by pretreatment with pertuεsis toxin (Table 2) . Table 2 cyclic AMP (% of control) control +PTx 0.5 mM Ca 2+ 100 106 + 8 2 . 0 mM Ca 2+ 19 + 4 94 + 2 0.5 mM Ca 2+, 200 μM Spermine 23 + 5 93 + 6 0.5 mM Ca , 30 μM Neomycin B 28 + 8 87 + 6 0.5 mM Ca 2+, 2 μg/ml Protamine 20 + 4 89 + 9 Pertusεiε toxin (PTx) blocks the inhibitory effects of extracellular Ca 2+ and molecular polycations on cyclic AMP formation. Bovine parathyroid cells were cultured for 16 h with or without 100 ng/ml pertusεiε toxin. The cellε were εubsequently washed and incubated for 15 min with 10 μM isoproterenol with or without the indicated concentrationε of extracellular Ca 2+ or molecular polycations. Total cyclic AMP (cellε + supernatant) was determined by RIA and the resultε are expressed as a percentage of the levels obtained in 0.5 mM Ca2+ (112 + 17 pmole/106 cells). Each value is the mean + SEM of three experiments. In human parathyroid cellε, extracellular Mg 2+ elicited a εustained, steady-state increase in [Ca 2+]. in addition to a rapid transient increase (Fig. 10). As in bovine parathyroid cells responding to extracellular Ca 2+, the steady-εtate increase in [Ca 2+]. evoked by Mg2+ in human parathyroid cells reεultε from Ca 2+ i.nflux through voltage-inεensitive channels (Fig. 10a). This effect of Mg 2+ on steady-state [Ca2+]. in human parathyroid cells is seen in both adenomatous and hyperplastic tiεsue. Neomycin B and spermine were tested for effects on [Ca 2+]• in human parathyroid cells prepared from adenomatous tissue. Representative results with neomycin B are shown in Fig. 19. Neomycin B caused not only a transient but additionally a steady-εtate increaεe in [Ca 2+]■ in human parathyroid cellε (Fig. 19a). Thuε, in human cells, the pattern of change in [Ca 2+]. evoked by extracellular Ca 2+, Mg2+ or neomyci.n B i.s very similar. Cytosolic Ca 2+ transientε elicited by neomycin B perεiεted in the preεence of La 3+ (lμM) and abεence of extracellular Ca 2+. Neomycin B therefore cauεes the mobilization of tracellular Ca 2+ in human parathyroid cells. Neomycin B inhibited PTH secretion from human parathyroid cellε at concentrationε that cauεed the mobilization of mtracellular Ca 2+ (Fig. 13). There were, however, εome differenceε in the reεponses of human and bovine parathyroid cellε to neomycin B. The EC-- of neomycm B for the mobi .li.zati.on of mtracellular Ca2+ waε 40 μM in bovine and 20 μM in human parathyroid cellε (cf. Figs. 13 and 15), whereas the potency of spermine was similar in bovine and human parathyroid cells (EC 5Q = 150 μM) . Thus, although bovine cells can be used for initial studieε to εcreen teεt molecules for activity, it is important to perform follow-up studies using human parathyroid cells. To asεeεε the effects of molecular polycations on C-cells, a neoplastic cell line, derived from a rat medullary thyroid carcinoma (rMTC 6-23 cellε) was used. Both spermine (10 mM) and neomycin B (5 mM) were without effect on basal [Ca 2+J. in these cells. Nor did either molecule affect the responεe to the εubεequent addition of extracellular Ca 2+. Repreεentative results documenting the lack of effect of neomycin B are shown in Fig 21. Neomycin B (1 mM) or spermine (1 or 5 mM) failed to evoke any increase in [Ca 2+]. in osteoclasts (Fig. 23). In the trace shown, there appeared to be some potentiation of the responεe to a subsequent increase in the concentration of extracellular Ca 2+, although this was not a consiεtent finding. In two other cellε, εpermine (5 mM) waε again without effect on baεal [Ca 2+]. and caused a small inhibition (about 15%) of the extracellular Ca 2+-induced increaεe in [Ca 2+].. In a third cell, neomycin B (5 mM) was without effect on basal [Ca 2+]. and did not affect increaseε in [Ca 2+]. elicited by extracellular Ca2+ The overall picture that develops from these studies is that spermine and neo mycin B are without effect on basal or stimulated levelε of cytosolic Ca 2+ in osteoclaεts. The failure of the molecular polycations to affect the Ca 2+-sensing mechanisms of C-cells or oεteoclaεts demonstrateε the ability to diεcover or deεign novel lead moleculeε that act specifically on the parathyroid cell Ca 2+ receptor or otherwise modulate one or more functions of the parathyroid cell's normal response to [Ca 2+ J. Screening of various other molecules iε described in detail below and the reεultε εummarized in Table 1. Example 2: Polyamine Screening Straight-chain polyamineε (εpermine, εpermidine, TETA, TEPA, and PEHA) and two derivativeε thereof (NPS 381 and NPS 382) were screened as in Example 1. These molecules were all found to mobi .li.ze m. tracellular Ca2+ in bovine parathyroid cellε. Their order of potency iε aε followε, with the net poεitive charge liεted in parentheses: Putrescine (+2) and cadaverine (+2) were inactive at a concentration of 2mM. Another straight-chain polyamine, DADD, behaved somewhat differently from the other polyamines and is described in Example 7. Example 3: Cyclic Polyamine Screening Two cyclic polyamines, hexacyclen and NPS 383, were screened as in Example IN Hexacyclen (+6, EC j - 0 = 20 μM) is 7-fold more potent than NPS 383 (+8, EC 5Q = 150 μM) . The converse would be expected based solely on net positive charge as the structural characteristic for Ca 2+ receptor activity. Example 4: Aminoglycoside Antibiotic Screening Six antibiotics were screened as in Example 1. The reεulting EC 'ε for the mobilization of intracellular Ca 2+, in rank order of potency, were: Table 4 Antibiotic EC 5Q (in μM) neomycin (+6) 10 gentamicin (+5) 150 bekanamycin (+5) 200 streptomycin (+3) 600 Kanamycin (+4.5) and lincomycin (+1) were without effect at a concentration of 500 μM. Within the aminoglycoside serieε, there iε a correlation between net poεitive charge and potency. However, neomycin iε conεiderably more potent than variouε polyamineε (NPS 381, NPS 382, NPS 383, PEHA) that have an equal or greater poεitive charge. Since aminoglycoεide antibiotics of this type have renal toxicity which may be related to interaction with calcium receptors in the kidney, such screening could be used to screen for toxicity in the development of new aminoglycoεide antibioticε. Example 5: Peptide and Polyamino Acid Screening Protamine and polymers of lyεine or arginine varying in peptide length were εcreened for their ability to mobilize intracellular Ca 2+ as in Example 1. The resulting EC 's for the mobilization of intracellular Ca 2+, in rank order of potency, we =rree:: Table 5 Peptide (MW in kD) EC 5Q (in nM) polyArg (100) 4 polyArg (40) 15 polyLys (27) 30 protamine (4.8) 75 polyArgTyr (22) 200 polyLys (14) 1000 polyLys (3.8) 3000 The net positive charge of these polymers increaseε as the MW increases. Thus, as for the aminoglycoεides, there is a direct correlation between net charge and potency among this serieε of polyamino acidε. Protamine is esεentially polyArg with a net poεitive charge of +21. Example 6: Arylalkylamine Screening Moleculeε selected from the clasε of arylalkylamine toxinε derived from the venomε of waεpε and εpiderε were εcreened aε in Example 1. Philanthotoxin-433 (+3) waε without effect at a concentration of 500 μM. It iε similar in structure to the argiotoxins described below. Argiotoxin-636 (400 μM) did not elicit increases in [Ca 2+]. but it did potentiate cytosolic Ca 2+ responses to the subsequent addi.ti•on of extracellular Ca 2+. This is a feature common to all molecules that activate the Ca 2+ receptor and is also seen with a variety of extracellular divalent cations. This is considered in more detail in Example 7. In contrast to argiotoxin-636, argiotoxin-659 elicited increaseε in [Ca 2+]. with an EC 5 _ of 300 μM. Argiotoxin-659 differs from argiotoxin-636 in having a hydroxylated indole moiety rather than a dihydroxyphenyl group. This is the only difference in the structure of these two molecules. Thus, the difference in potency lies in the nature of the aromatic group, not in the polyamine chain which carries the positive charge. Example 7: Screening of Ca— 2+ Channel Blockers Ca 2+ channel blockerε, i.e., thoεe molecules which block influx of extracellular Ca 2+ through voltage- senεitive Ca 2+ channelε, were εcreened aε in Example 1. There are three εtructural claεεeε of Ca 2+ channel blockerε: (1) dihydropyridineε, (2) phenylalkylamineε, and (3) benzothiazipineε. None of the dihydropyridineε teεted (nifedipine, nitrendipine, BAY K 8644, and (-) 202-791 and (+) 202- 791) had any effect on baεal [Ca 2+]. or increases in [Ca 2+]. evoked by extracellular Ca2+ when they were tested at 1 μM. Previous studies showed that parathyroid cells lack voltage-εenεitive Ca 2 >++ channels, but do have voltage-insensitive Ca .2 -1 + channelε that are regulated by the Ca 2+ receptor. The phenylalkylamineε examined were verapamil, D- 600 (a methoxy-derivative of verapamil), TMB-8, and an analog of TMB-8, NPS 384. The firεt three moleculeε were teεted at a concentration of 100 μM. The phenylalkylamineε behaved differently from other moleculeε examined. They evoked no change in [Ca 2+]. when added to cells bathed in buffer containing a low concentration of extracellular Ca 2+ (0.5 mM) . However, verapamil, D-600, and TMB-8 potentiated the mobilization of mtracellular Ca 2+ elicited by extracellular divalent cations and they additionally blocked the influx of extracellular Ca 2+. At intermediate levelε of extracellular Ca2+ (1-1.5 mM) , these molecules were capable of evoking a small but robust increase in [Ca 2+]. that arose from the mobilization of tracellular Ca 2+ The phenylalkylamines act differently than organic polycationε like neomycin. The data εuggeεt that verapamil, D-600 and TMB-8 are partial agoniεtε or alloεteric activators at the Ca 2+ receptor, in contraεt to the other moleculeε examined which are full agonists. Molecule NPS 384, at a concentration of 300 μM, did not evoke an increase in [Ca 2+]. but it blocked influx of extracellular Ca 2+. Testing at higher concentrations may reveal an ability of this molecule to cause the mobilization of tracellular Ca 2+. While the ability of these molecules to block influx is intriguing and not entirely unexpected, it is the ability of these molecules to evoke transient increaεeε in [Ca2+]. (arising from intracellular Ca 2+ mobilization) that is important. Considerable experience with measurements of [Ca 2+]. in parathyroid cells shows that transient increases in [Ca 2+] . almost invariably result from the mobiliz 1 ation of m. tracellular Ca2+ and therefore reflects activation of the Ca 2+ receptor. The benzothiazipine examined, diltiazem, was similar in all respects to verapamil and D-600 and was also effective at 100 μM. It should be mentioned that with the exception of the phenylalkylamines, all the active molecules teεted above evoke increaεe in [Ca 2+]• that are of magnitude similar to that evoked by a maximally effective concentration of extracellular Ca 2+. This shows that these molecules are equally efficacious aε extracellular divalent cations. This contrasts with the activity of phenylalkylamines, which seem to act only as partial agoniεtε. Amongεt the phenylalkylamineε, some interesting structure-activity relationshipε emerge. Significant iε the different potencies of molecules like TMB-8 and NPS 384. TMB-8 potentiated transient increases in [Ca 2+ ] i at 100 μM whereas NPS 384 fails to do so even at 300 μM, yet these molecules carry the same net poεitive charge. It follows that εome other εtructural feature, unrelated to net charge, impartε greater potency to TMB-8. Example 8: Molecule Screening on Human Parathyroid Cellε Spermine and neomycin were teεted for effectε on [Ca 2+]. in human parathyroid cellε obtained from glandε removed by surgery and prepared as in Example 1. In human parathyroid cells, εpermine waε found to cause only a small increase in [Ca 2+]. when tested at a concentration of 300 μM. Neomycin, on the other hand, evoked a large increaεe in [Ca 2+]. in human parathyroid cellε when teεted at a concentration of 20 μM. The magnitude of the reεponse elicited by neomycin was equal to that evoked by a maximally effective concentration of extracellular Ca 2+ Example 9: Molecule Screening on Xenopus Oocyteε Ooσyteε injected with mRNA from human parathyroid cellε expreεs the Ca 2+ receptor and mobilize intracellular Ca 2+ i•n response to a variety of extracellular inorganic di- and trivalent cations. Using this screen allows one to test for an action directly on the Ca 2+ receptor. Oocyteε expreεεing the Ca 2+ receptor also responded to εeveral moleculeε active on intact parathyroid cellε when εcreened aε followε. Hexacyclen caused the mobilization of mtracellular Ca 2+ at a concentration of 135 μM. Neomycin (100 μM) and NPS 382 (5 mM) were alεo effective. This offers rather compelling evidence εhowing that these moleculeε act on the Ca 2+ receptor or on εome other protein intimately aεεociated with itε function. For example, we have been able to detect Ca 2+ receptor expreεsion in oocytes by measuring 45Ca2+ mobilization. In these experiments, oocytes were injected with bovine parathyroid mRNA or water and, after 72 hours exposed to serum or 10 mM neomycin. Prior to being stimulated, oocytes were loaded with 45 Ca2+. Sti.mulati.on wi.th serum for 20 min resulted in intracellular 45Ca2+ release representing a 45% increase compared to mock challenge with buffer. Challenge with 10 mM neomycin for 20 min. resulted in a 76% increaεe in 45Ca2+ release. The asεay is εenεitive enough for uεe m cloning the Ca 2+ receptor, and haε the advantage of a higher throughout than the electrophysiological measurement of Ca 2+ activated Cl ~ current. In another example, human osteoclastoma tisεue waε obtained from bone biopεy tiεεue. Oocyteε injected with mRNA iεolated from this tisεue were challenged with 30 mM Ca 2+. Controlε did not reεpond while 8 of 12 oocyteε injected with oεteoclaεtoma mRNA reεponded appropriately (Fig. 34). Theεe experimentε provide the firεt evidence that the Ca 2+ reεponεe of oεteoclasts to extracellular Ca 2+ i.s m fact genetically encoded. The results also indicate that the osteoclaεt Ca 2+ receptor may be cloned by expreεεion in Xenopuε oocyteε. Example 10: Molecule Screening on Rat Oεteoclaεtε The different εenεitivitieε of parathyroid cellε and rat osteoclastε to extracellular Ca 2+ εuggeεt that their Ca 2+ receptors are different. While parathyroid cellε respond to extracellular Ca 2+ concentrations between 0.5 and 3 mM, osteoclaεtε reεpond only when the level of extracellular Ca2+ creaεes beyond 5 mM. This rather high concentration of Ca 2+ is nonetheless physiological for osteoclasts; as they reεorb bone, the local concentration of extracellular Ca 2+ may reach levelε aε high aε 30 mM. Molecule εcreening with rat oεteoclasts was performed as follows. Osteoclaεtε were obtained from the long bones of neonatal rats. [Ca 2+]. was measured in εingle cells using the fluorimetric indicator indo-1. Spermine, spermidine, neomycin, and verapamil were tested, and none of these caused any large increase in [Ca 2+]. in oεteoclaεts (although εmall reεponεeε were detected) . At a concentration of 1 mM, spermidine caused a small increase in [Ca 2+]. (about 10% of that evoked by a maximal concentrati •on of extracellular Ca2+) . Neither neomycin (10 mM) nor spermine (10 or 20 mM) caused increaseε in [Ca 2+]. in rat oεteoclasts. Neomycin (10 mM) did not block the increase in [Ca 2+]• elicited by the subsequent addition of 25 M extracellular Ca 2+. Pretreatment with spermine (20 mM) , however, did depreεs the responεe to extracellular Ca 2+. Verapamil (100 μM) caused no detectable increaεe in [Ca 2+]. but it did block the reεponse to extracellular Ca 2+ Comparisonε between oεteoclaεts and parathyroid cellε εhow that molecules active on the latter are relatively ineffective in osteoclasts. This demonstrates that drugs that target a specific Ca + receptor without affecting those receptor types present on other Ca 2+-sensing cells are readily developed. Similarly, drugs active at two or more such Ca 2+ receptors may also be developed. Screening for Calcimimetic and Calcilytic Activity on the Osteoclast Calcium Receptor Compounds posseεεing activity on the oεteoclast calcium receptor can be discovered by measuring [Ca 2+]. in single rat osteoclastε aε deεcribed above. An improved aεsay enables moderate-to-high levels of compound throughout. This new method is based on the use of rabbit osteoclaεtε which can be obtained in high yield (10 per animal) and purity (95% of the cellε are osteoclasts). The purity of the rabbit oεteoclaεt preparation allowε meaεurementε of [Ca 2+]. to be performed on populationε of cellε. Because the recorded fluorescence signal is an averaged population response, intercellular variability is minimized and .the precision of the asεay is greatly increased. This, in turn, enables more compoundε to be εcreened for activity. Rabbit oεteoclaεtε are prepared from 6-day old bunnieε. The animalε are εacrificed by decapitation and the long boneε removed and placed into oεteoclaεt medium (OC medium: alpha-minimum eεεential medium containing 5% fetal bovine serum and penicillin/streptomycin) . The boneε are cut into sections with a scalpel and placed in 2 ml of OC media in a 50 ml conical centrifuge tube. The bone sections are minced with scisεorε until a fairly homogeneous suspenεion of bone particleε iε obtained. The εuεpenεion is then diluted with 25 ml of OC media and the preparation swirled gently ("vortexed") for 30 secondε. The bone particleε are allowed to εettle for 2 minuteε after which the supernatant is removed and added to a 50 ml centrifuge tube. The bone particleε are resuspended in OC media, swirled, sedimented and harvested as just described. The εupernatantε from the two harveεtε are combined and centrifuged and the reεulting cellular pellet resuspended in Percoll. The suεpenεion is then centrifuged and the white viscous band just below the meniscuε is removed and washed with OC media. The Percoll centrifugation step results in a significant improvement in purity and allows osteoclaεtε to be plated at high denεities, suitable for measuring [Ca 2+]. m populationε of cellε. The cellε are plated onto glaεε cover slips appropriate for measuring [Ca 2+]. according to one of the methods described below. If necesεary, the purity of the preparation can be improved " . In this case, the cells are cultured overnight and then rinsed with Ca 2+- and Mg2+-free buffer. The cell monolayer is then immersed in Ca 2+- and Mg 2+-free buffer containing 0.02% EDTA and 0.001% pronase for 5 min. Thiε buffer iε then removed and replaced with OC media and the cellε allowed to recover for 1 to 2 hourε before loading the cells with fluorimetric indicator and measuring [Ca 2+] . as described below. In one embodiment, thiε technique allowε the measurement of in populations of osteoclastε using fluorescence microscopy. The purified osteoclaεts are allowed to attach to 25 mm diameter glaεε cover slips and then loaded with indo-1. The cover slips are secured into a superfusion chamber and placed onto the stage of a fluorescence microscope. The use of a low power objective (x4) allows a field containing 10 to 15 osteoclasts to be visualized. In one variation, the fluorescence of each cell in the field can be recorded simultaneouεly and εtored εeparately for later analyεis. Changeε in [Ca 2+]. of each cell can be eεtimated and the average reεponεe of all cellε in the field calculated. In another variation, the fluorescence from the entire field of cells can be recorded and processed immediately. In either variation, the final data is in the form of an average responεe from the cellε preεent in the microεcopic field. Because of thiε, intercellular variability iε minimized and preciεion of the aεεay greatly increaεed. Thiε method enables 10-20 compounds per week to be screened for activity on the osteoclaεt calcium receptor In a more preferred embodiment, thiε technique allowε the meaεurement of [Ca 2+]. in populations of osteoclasts using a conventional fluorimeter. The purified osteoclasts are allowed to attach to rectangular glass cover slips. In one variation, a standard quartz cuvette (1cm ) is used and the glaεε coverεlipε are 2 x 1.35 cm. In another variation, a 2 microcuvette lε used (0.5 cm ) and the glass coverslips are 1 x 0.75 cm. In either case the cells are loaded with fura-2 or some other suitable fluorimetric indicator for measuring [Ca 2+] .. The fluorescence of indicator-loaded cells is recorded as deεcribed above for bovine parathyroid cellε. This method allows a higher throughput than fluorescence microscopy and enableε 20-50 compoundε per week to be evaluated for activity on the osteoclast calcium receptor. In a most preferred embodiment, the technique can be used to measure [Ca 2+]. in osteoclastε in a 96-well plate. The purified oεteoclaεtε are plated at high denεity into each well of a 96-well plate and εubεequently loaded with a suitable fluorimetric indicator. The fluorescence of each well iε recorded using a fluorimetric plate reader. Thiε method haε the potential of becoming fully automated uεing roboticε a would enable high throughput screening in which 50 to 100 compounds per week could be screened. Other Ca— 2+ Receptor Examples The following examples demonstrate that, just as there are subtypes of receptors for molecular ligands, εo too do there appear to be εubtypeε of Ca 2+ receptorε that can be differentially affected by drugε. The parathyroid cell Ca 2+ receptor senses levels of extracellular Ca 2+ around 1.5 mM whereaε the Ca2+ receptor on the oεteoclast respondε to levelε around 10 mM (Fig. 22). Neomycin or spermine, which activate the parathyroid cell Ca 2+ receptor, fail to affect the Ca 2+ receptors on C-cells or oεteoclaεts (Figs. 21 and 23). These data conεtitute the firεt evidence for pharmacologically distinct subtypeε of Ca 2+ receptoi and theεe data are being uεed to deεign and develop drugs that act selectively on a particular type of Ca2+. receptor. Indeed, testing of lead molecules demonstrate such cell-specific effects. For example, NPS 449, which elicits increaεeε in [Ca 2+]. in oεteoclaεts is without effect on [Ca 2+]. in parathyroid cellε. Conversely, NPS 447, which activates the parathyroid cell Ca 2+ receptor, is effective in activating the osteoclaεt Ca 2+ receptor only at concentrations 10-fold higher. Finally, agatoxin 489, although not very potent in activating the C-cell Ca 2+ receptor ( C 5Q = 150 μM) , is a quite potent activator of the parathyroid cell Ca receptor (EC 5Q = 3 μM) . The lead molecules presently under development will affect selectively the activity of a specific type of Ca 2+-sensing cell in vivo. Drugs with lesε εpecificity might not neceεεarily be therapeutically undeεirable. Thuε, depreεεing oεteoclaεt activity and stimulating calcitonin secretion are two different approaches to inhibiting bone resorption. Drugs that target the Ca 2+ receptors on both of these cells might be very effective therapies for osteoporosis. Because PTH is also involved in regulating bone metabolism, drugs acting on the parathyroid cell Ca 2+ receptor may also be useful in the treatment and/or prevention of osteoporoεiε. Reεultε of εome teεt moleculeε are shown below. In Table 6, the comparative activity of calcimimetic molecules is shown. Bovine parathyroid cells and C- cellε (rMTC 6-23 cellε) were loaded with fura-2, and rat oεteoclaεts with indo-1 and the potency of the indicated molecules to mobilize intracellular Ca2+ determined by constructing cumulative concentration-responεe curveε. Moleculeε liεted aε "inactive" did not alter [Ca 2+] 1. when tested at a concentration of 1 mM . Table 6 EC S0 (μM) COMPOUND PARATHYROID OSTEOCLAST C-CELL NPS R-568 0.60 200 >300 NPS S-568 30 NPS R-467 2 >100 NPS S-467 >30 NPS 017 6 inactive 150 NPS 447 9 150 NPS 456* 15 • 200 >100 NPS 015 22 inactive NPS 109 40 >300 5 NPS 449 inactive 150 NPS 468* 30 250 spermine 150 inactive inact ive neomycin 40 inactive inact ive • racemic mixture; " inactive" is defined as causing no increase in cytosolic Ca 1 ' at a concentration of 1-5 mM. *racemic mixture; "inactive" is defined as causing no increase in cytosolic Ca + at a concentration of 1-5 mM. Example 11: Lead Molecules for Parathyroid Ca— Receptor Structure-activity studieε uεing polyamineε and arylalkylamines led to the testing of molecules structurally akin to NPS 456. NPS 456 is a potent activator of the. parathyroid cell Ca 2+ receptor. This molecule is notable because it possesε only one poεitive charge yet iε much more potent than many polybasic molecules. Brief (2 min) pretreatment with PMA shiftε the concentration-reεponεe curve for NPS 456 to the right. This indicateε that NPS 456 acts through the same mechaniεm uεed by extracellular Ca 2+. NPS 456 evokeε the mobi .li.zati.on of m. tracellular Ca2+ in Xenopuε oocyteε expreεεing the parathyroid cell Ca 2+ receptor, which de onεtrateε a direct action on the Ca 2+ receptor (Fig. 33). Moreover, NPS 456 containε a chiral carbon, and therefore exiεtε in two iεomeric formε. Both iεomerε have been εyntheεized and examined for activity. The R-iεomer, NPS 447, iε 12 timeε more potent than the S-iεomer, NPS 448 (Fig. 28). Thiε is the first demonstration that a Ca 2+ receptor can recognize an organic molecule in a stereospecific manner. Because NPS 447 is a structurally simple molecule with selective and potent effects on the parathyroid cell Ca 2+ receptor, structure-activity studieε around thiε lead molecule are εimple. The aim of theεe εtudieε iε to generate an array of related moleculeε with variouε characteriεticε from which the final development candidate can be εelected. Thiε effort haε already revealed εome of the structural domains of NPS 447 that contribute to activity and potency. For example, the novel compound NPS 459 is an analog of NPS 447 that is smaller (MW < 240) yet nearly aε potent aε the parent molecule, whereas several other analogs are relatively inactive. The most intereεting moleculeε from this analog project can be put into in vivo testing for effectε on PTH εecretion and εerum Ca 2+ levelε (see Examples 15, 16, 17, 18 and 23). The novel compound NPS 467 iε an even smaller molecule than NPS 447 yet the former is about 3-fold more potent than the latter in causing increaεeε in [Ca 2+ ] i in parathyroid cellε. Like NPS 456, NPS 467 is a racemic mixture. Resolution of NPS 467 into its enantiomers provides an iεomer of even greater potency than the racemic mixture (εee Example 16). Further εtructure-activity εtudieε on molecules related to NPS 447, NPS 467 and NPS 568 are expected to yield pure isomerε with greater potency than theεe moleculeε in their racemic formε. Reεultε obtained with NPS 456 (Fig. 33) εhow that it elicitε oεcillatory increaεeε in Cl- current at concentrationε of 100 μM. NPS 456 iε the moεt potent molecule activate on Xenopuε oocyteε expreεsing the parathyroid cell Ca 2+ receptor. The reεultε obtained in thiε expreεεion εystem with neomycin and NPS 456 demonstrate that theεe moleculeε act directly on the Ca 2+ receptor. Example 12: Oεteoclaεt Ca— 2+ Receptor Lead Moleculeε The εtrategy used for elucidating the mechanism of action of extracellular Ca 2+ on the osteoclaεt was similar to that proven effective in parathyroid cells. The first experiments examined the effectε of La 3+ on [Ca 2+]. in εingle rat oεteoclaεtε loaded with the fluorimetric indicator indo-1. As described above, trivalent cations like La 3+ are impermeant and block Ca 2+ influx. Low micromolar concentrati.ons of La3+ partially depresεed extracellular Ca 2+-i.nduced increaεes in [Ca 2+]. (Fig. 29). The demonstration of a La 3+-resistant increase in [Ca2+]. provides evidence for the mobilization of mtracellular Ca 2+ The results of these experiments parallel those obtained in parathyroid cells and suggest that similar mechanisms are used by extracellular Ca 2+ to regulate [Ca2+]. in both cell types. Another series of experiments εhowed that extracellular Mn 2+ evoked tranεient increaεeε in [Ca 2+]. (Fig. 30(a)) that perεiεted in the absence of extracellular Ca 2+ (Fig. 30B) . These results are likewiεe indicative of the mobilization of intracellular Ca 2+. Although Mn2+ can enter εome cellε, it iiεε unlikely to do so in the osteoclaεt becauεe Mn.2+ quencheε the fluoreεcence of indo-1. Thuε, if Mn 2+ penetrated intracellularly, a decreaεe, not an increaεe in the fluoreεcent εignal would be obεerved. The reεultε obtained with a variety of di- and trivalent cationε are all conεiεtent with the preεence of a Ca 2+ receptor on the εurface of the osteoclast that is coupled to the mobilization of intracellular Ca 2+ and influx of extracellular Ca2+ through voltage-insenεitive channelε. Reεults show evidence for genetic material in human osteoclaεtε that encodeε a Ca 2+ receptor protein (εee below). Tranεient increases in [Ca 2+]. resulting from the mobilization of intracellular Ca2+, are sufficient to inhibit osteoclaεtic bone reεorption m vitro. Thuε, aε with the parathyroid cell, activation of the Ca 2+ receptor appears to be a viable means of inhibiting the activity of osteoclastε. NPS 449 iε presently the lead molecule for calcimimetic drugs on this receptor. It is a small molecule (MW < 425) and it mobilizes intracellular Ca 2+ in rat oεteoclaεts with a EC 50 of about 150 μM (Figs. 31A and 31B) . Although the potency of NPS 449 iε relatively low, it haε a εimple εtructure with only one poεitive charge and iε expected to have deεirable pharmacodynamic and pharmacokinetic propertieε. NPS 449 waε examined for itε ability to inhibit bone reεorption m vitro. Thiε waε done by morphometric analyεiε of pit formation on thin εliceε of bovine cortical bone using scanning electron microscopy. Rat osteoclaεtε were incubated for 24 hours in sliceε of bone in the presence or abεence of variouε concentrationε of NPS 449. NPS 449 cauεed a concentration-dependent inhibition of bone reεorption with an IC 5Q of 10 μM. The anticipated results provide the first demonstration that molecules acting at this novel site can inhibit osteoclastic bone resorption. More potent analogε of NPS 449 will be generated using synthetic chemistry and will be tested and asεayed uεing the methodε deεcribed herein. Example 13: C-Cell Ca—2+ Receptor Lead Moleculeε Activation of the C-cell Ca 2+ receptor stimulates the secretion of calcitonin which then acts on osteoclaεtε to inhibit bone reεorption. Calcimimetic drugε εelectively affecting C-cellε are uεeful in the treatment of oεteoporoεiε. The mobilization of mtracellular Ca 2+ iε used aε a functional index of Ca 2+ receptor activity. The εcreening effort in C-cells is facilitated by the availability of cultured cell lines expreεεing the C- cell phenotype (e.g. , rat medullary thyroid carcinoma cellε; rMTC 6-23 cellε). Selected for initial εtudy were three arylalkylamine moleculeε. Two are naturally occurring (agatoxin 489 and agatoxin 505) and the other (NPS 019) iε a synthetic agatoxin analog. Agatoxin 505 waε found to block extracellular Ca 2+-induced increaεeε in [Ca 2+]., with an IC 5Q of 3 μM. The inhibitory effect reεulted from a block of the L-type voltage-εenεitive Ca 2+ channel preεent in theεe cellε. In contraεt, agatoxin 489 waε found to mobilize mtracellular Ca 2+ in rMTC cellε with an EC 5Q of 150 μM. Thiε was the first organic molecule diεcovered that waε found to activate the C-cell Ca 2+ receptor. The synthetic analog, NPS 019, was even more potent and mobilized mtracellular Ca 2+ with an EC 5,.,0.. of 5 μM (Fig. 32). It is significant that the only structural difference between NPS 019 and agatoxin 489 is the presence or absence of an hydroxyl group. The fact that such subtle differences in structure affect profoundly the potency of molecules indicates a structurally specific binding site on the Ca2+ receptor. This, in turn, encourages the view that very potent and selective activators of Ca 2+ receptors can be developed. NPS 019, which iε a small molecule (MW < 500), iε a lead molecule for development of calcimimetics of the C-cell Ca 2+ receptor and can be tested for its ability to stimulate calcitonin εecretion in vitro. Subεequent in vivo teεting will then determine the ability of this molecule to stimulate calcitonin secretion and inhibit bone resorption. These m vivo studies will be performed in rats. The results obtained in these studieε, which are anticipated to be poεitive, will provide the firεt evidence εhowing that a small organic molecule acting on a novel receptor can stimulate calcitonin secretion and depresε bone reεorption. Example 14: Calcilytic Activity of NPS 021 on Parathyroid Cells For a compound to be considered a calcilytic, it must block the effects of extracellular Ca 2+ or a calcimimetic compound on an extracellular Ca 2+-senεing cell. An example of a calcilytic compound iε NPS 021, the εtructure of which iε provided in Fig. 1. In bovine parathyroid cellε loaded with fura-2, NPS 021 blockε increases in [Ca 2+]. elicited by extracellular Ca 2+ . The IC 50 of NPS 021 for blocking this responεe iε about 200 aM and, at concentrationε around 500 aM, the increase in [Ca 2+] . evoked by extracellular Ca 2+ l.ε aboliεhed X . Significantly, NPS 021 doeε not by itself cause any change in [Ca 2+] . when teεted at low [Ca 2+ ] (0.5 mM; Fig. 37). Ga 3+ is also calcilytic to Xenopus oocytes expressing the cloned Ca 2+ receptor: Ga3+ by itse Ilff has no effect on the Cl currents activated by Gd3+ calcimimetic, but pretreatment with Ga 3+ blockε the action of Gd ,3'+ Example 15: NPS 467 Lowerε Serum Ionized Calcium Compoundε εhown to activate the bovine parathyroid cell Ca 2+ receptor in vitro were teεted for hypocalcemic activity m vivo. Male Sp ague-Dawley rateε (200 g) were maintained on a low calcium diet for one week prior to receiving teεt εubεtance or vehicle aε control. Blood waε collected from the tail vein three hourε after the intra-peritoneal administration of NPS 467. Ionized Ca 2+ in whole blood or serum was measured with a Ciba- Corning 634 Analyzer according to the inεtructionε provided with the inεtrument. Serum total calcium, albumin and phoεphate were meaεured by techniqueε well known in the art. NPS 467 cauεed a doεe-dependent reduction in εerum or whole blood Ca 2+ (Fig. 38). The fall in blood Ca 2+ at thiε time waε paralleled by a proportional fall in the levelε of blood total calcium. There waε no change in εerum albumin or phoεphate levelε at any of the doεeε examined. In preliminary studies, NPS 467, at doseε effective in lowering blood Ca 2+, cauεed a doεe-dependent reduction in circulating levelε of PTH (Fig. 39). The hypocalcemic effect of NPS 467 waε maximal within three hourε and returned toward control levelε after 24 hourε (Fig. 40). NPS R-467 (εee Example 16) waε alεo effective in lowering εerum ionized Ca 2+ i.n ratε mai.ntained on a normal, calcium-replete diet. A single dose of NPS R-467 (10 mg/kg i.p.) caused a rapid fall in serum levelε of ionized Ca 2+ which were maximal by 1 hr (22% decreaεe from the control level) and remained depreεεed at or near this level for up to 6 hours. Example 16: NPS 467 Lowers Serum Ionized Calcium in a Stereospecific Manner NPS 467 iε a racemic mixture. Reεolution of NPS 467 into its two enantiomers was achieved by separation on a chiral column. The R-isomer was about 100-fold more potent than the S-isomer in activating the bovine parathyroid cell Ca 2+ receptor m, vitro as aεεeεεed by the ability of the enantiomerε to evoke increaεeε in [Ca 2+]. in parathyroid cellε (Fig. 41). Likewise, similar resolution of the novel compound NPS 568 into its enantiomers showed that the R-isomer was 40-fold more potent than the S-isomer in causing the mobilization of intracellular Ca 2+ in bovine parathyroid cells (see Table 6, supra) . The isomerε of NPS 467 were examined for effects on serum Ca 2+ as m Example 15. Consiεtent with the in vitro reεults, the R-isomer of NPS 467 proved to be more potent than the S-isomer in lowering serum Ca 2+ in vivo (Fig. 42; each compound was tested at a concentration of 5 mg/kg body weight) . Example 17: NPS 467 Lowers Serum Ionized Calcium in an in vivo Model of Secondary Hyperparathyroidism An accepted and widely used animal model of secondary hyperparathyroidism arising from chronic renal failure is the 5/6 nephrectomized rat. Animals receiving such surgery become initially hypocalcemic and, to maintain serum Ca 2+ levels, there is a compensatory hyperplasia of the parathyroid glands and elevated levels of circulating PTH. Male Sprague-Dawley rats (250 g) received a 5/6 nephrectomy and were allowed to recover for 2 weeks. At this time they were normocalcemic (due to elevated levelε of εerum PTH). The adminiεtration of NPS R-467 (10 mg/kg i.p.) cauεed a rapid (within 2 hourε) fall in serum ionized Ca 2+ levels to 83% of controlε in an animal model of εecondary hyperparathyroidism. This suggests that compounds of this sort will effectively depresε PTH εecretion in patientε with εecondary hyperparathyroidism and hyperplastic parathyroid glandε. Example 18: NPS 467 Failε to Lower Serum Ionized Calcium Levels in Parathyroidecto ized Animals To determine the primary target tissue upon which NPS 467 acts to cause a hypocalcemic responεe, the para thyroid glandε in ratε were surgically removed. Animals receiving a total parathyroidectomy become hypocalcemic and are largely dependent upon dietary calcium to maintain serum Ca 2+ ho eostaεiε. Parathyroidectomized animals had serum ionized Ca 2+ levels of 0.92 mM which fell gradually to 0.76 mM after 6 hours of fasting. The administration of a εingle doεe of NPS R-467 (10 mg/kg i.p.) did not cauεe any change in εerum ionized Ca levelε over a period of 6 hourε. These results demonstrate that intact parathyroid glands are required for the hypocalcemic effects of NPS R-467. The data additionally demonstrate that NPS R-467 can target the parathyroid glands m vivo. The resultε are consistent with the view that NPS R-467 acts on the parathyroid cell Ca 2+ receptor m vivo to depress secretion of PTH and thereby cauεe εerum levels of ionized Ca 2+ to fall. Example 19: NPS 467 Increases Intracellular Calcium in Human Parathyroid Glands Dissociated parathyroid cellε were prepared from a parathyroid adenoma obtained by εurgery from a patient with primary hyperparathyroidism. The cells were loaded with fura-2 and [Ca 2+]. measured as described above. Both NPS R-467 and NPS R-568 caused concentration- dependent increase in [Ca 2+].. The EC 50 's for NPS R-467 and NPS R-568 were 20 and 3 μM, respectively. Both these compounds are thus able to increase [Ca 2+]■ in pathological human tisεue and would thus be expected to decrease serum levels of PTH and Ca 2+ in patients with primary hyperparathyroidism. Example 20: Mechanism of Action of NPS 467 at the Para thyroid Cell Calcium Receptor Disεociated bovine parathyroid cells were used to further explore the mechanism of action of NPS 467 at the receptor level. In the presence of 0.5 mM extracellular Ca 2+, NPS R-467 caused a rapid and tranεient increaεe in [Ca 2+]■ which perεiεted in the preεence of 1 μM La 3+ and waε partially depreεεed by pretreatment with PMA (100 nM for 2 min.). All theεe results are consiεtent with an action of NPS R-467 on the Ca 2+ receptor. However, the cytoεolic Ca2+ response to NPS R-467 was abolished when parathyroid cells were suspended Ca 2+-free buffer. This suggests that NPS R- 467 cannot, by itself, cause the mobilization of mtracellular Ca 2+. It does, however, elicit responεes in parathyroid cells and in oocytes when a small amount of extracellular Ca 2+ is present. This suggeεts that partial occupancy of the Ca 2+-binding site is required for NPS R-467 to elicit a responεe. To teεt this hypothesiε, parathyroid cells were suεpended in Ca 2+-free buffer and exposed to a submaximal concentration of neomycin. Neomycin waε used because it mimics, in nearly all reεpectε, the effectε of extracellular Ca 2+ on parathyroid cellε and on Xenopuε oocyteε expressing the parathyroid cell Ca 2+ receptor. The addition of 10 aM neomycin did not by itεelf cauεe an increaεe in [Ca 2+]. under theεe conditionε. However the εubεequent addition of NPS R-467 (30 μM) now elicited a tranεient increase in [Ca 2+]. which, because there was no extracellular Ca 2+ present, must have come from the mobilization of intracellular Ca 2+. When cellε bathed in Ca2+-free buffer were expoεed to 30 aM NPS R-467 there waε no increaεe in [Ca 2+].. This concentration of NPS R- 467 iε maximally effective in increaεing [Ca 2+] . when extracellular Ca 2+ (0.5 mM) iε preεent. Ho 1 wever, the εubεeguent addition of 10 μM neomycin now evoked a tranεient increaεe in [Ca 2+] .. Preεumably, neomycin bindε to the same site as extracellular Ca 2+ and can functionally subεtitute for it. Using a submaximal concentration, which by itself causeε no reεponse, achieveε partial occupancy of the Ca2+-binding εite and allowε activation of the Ca 2+ receptor by NPS R-467. Additional studies to further define the mechanism of action of NPS R-467 were performed. The cellε were once again εuspended in Ca 2+-free buffer to insure that any observed increase in [Ca 2+]. resulted from the mobilization of mtracellular Ca 2+ In these experiments, however, a maximally effective concentration (100 μM) of neomycin was used. In the abεence of extracellular Ca 2+, 100 μM neomycin evoked a rapid and transient increase in [Ca 2+].. The subεequent addition of 30 μM NPS R-467 did not cauεe an increaεe in [Ca 2+].. In the converεe experiment, 30 μM NPS R-467 was added before 100 μM neomycin. As expected, NPS R-467 did not cause any increaεe in [Ca 2+].. It did not, however, affect the increaεe in [Ca 2+]. evoked by the εubεequent addition of 100 μM neomycin. These resultε, obtained with maximally effective concentrationε of NPS R-467 and neomycin, εuggeεt that theεe two compoundε do not act at the εame site. Rather, the results can be sufficiently explained by postulating two separate siteε on the Ca 2+ receptor, one to which extracellular Ca2+ and neomycin bind, and another to which NPS R-467 and εtructurally related compoundε (εuch aε NPS R-568) bind. Ligand binding to the former εite can reεult in full activation of the Ca 2+ receptor whereaε ligand binding to the latter εite can only occur and/or be functionally relevant when the extracellular Ca2+-binding εite lε occupied to εome as yet undefined degree. It is possible that ligand binding to the extracellular Ca 2+- binding site exposes a previously occluded binding site for NPS R-467. It appears that the NPS R-467-binding εite iε an alloεteric εite that augmentε receptor activation in reεponεe to ligand binding at the extracellular Ca 2+-binding site. The data demonstrate that the parathyroid cell Ca 2+ receptor posεeεεeε at leaεt two diεt ct εiteε for organic ligandε. One εite bindε the phyεiological ligand, extracellular Ca 2+, and certain organic polycationε like neomycin. Binding to thiε εite reεult in full activation of the Ca 2+ receptor, an increaεe in [Ca 2+]. , and the inhibition of PTH εecretion. NPS R-467 and NPS R-568 define a previouεly unrecognized binding εite on the Ca 2+ receptor. Binding to thiε εite can only occur and/or reεultε in full activation of the Ca 2+ receptor when the extracellular Ca 2+-binding εite ιε partially occupied. Ligandε acting at either εite are effective in εuppreεsing serum Ca 2+ levels m vivo. Alloεteric Site on Parathyroid Cell Calcium Receptor Calcimimetic compoundε that activate the bovine parathyroid cell calcium receptor, such as NPS R-467 and NPS R-568, do not cause the mobilization of intracellular Ca 2+ i.n the absence of extracellular Ca 2+. Rather, they increaεe the εenεitivity of the Ca 2+ receptor to acti•vati•on by extracellular Ca2+, thuε cauεing a shift to the left in the concentration- reεponεe curve for extracellular Ca 2+. Becauεe of thiε, it is unlikely that they act at the same site on the receptor as does extracellular Ca 2+. In contrast, organic and inorganic polycations do cause the mobilization of intracellular Ca 2+ in the absence of extracellular Ca 2+ and therefore probably act at the εame εite aε does extracellular Ca 2+. Compounds like NPS R-568, presumably act in an allosteric manner and their activity iε dependent on εome minimal level of extracellular Ca 2+. This suggests that partial occupancy of the extracellular Ca 2+-binding site on the receptor is required for compounds like NPS R-568 to be effective. This model is consistent with the obεervationε described in Example 20. Other details of the mechanism of action of NPS R- 568 on the parathyroid cell Ca 2+ receptor, however, are more accurately investigated by binding studies in 3 which the specific binding of radiolabeled (uεing H for example) NPS R-568 is assessed. There are several molecular mechanismε that could explain the activity of NPS R-568 on the parathyroid cell Ca 2+ receptor. In one mechanism (model 1), NPS R-568 could bind to the Ca 2+ receptor at a site that, when occupied, is not sufficient to activate the receptor functionally. Activation only occurs when some level of occupancy of the extracellular Ca 2+-binding site(ε) is achieved. In an alterative mechanism (model 2), the occupation of the extracellular Ca 2+-binding site could unmask latent binding siteε for compoundε εuch aε NPS R-568. Occupancy of thiε latent εite by NPS R-568 then increaεes the affinity and/or efficacy of binding at the extracellular Ca2+ site. Either mechanism involves a form of allosteπc activation of the Ca 2+ receptor by compounds such as NPS R-568. These are not the only posεible mechanisms that could explain the effect of compoundε like NPS R-568 on the parathyroid cell Ca 2+ receptor. Other mechaniεmε of action may be suggested by the resultε of the binding εtudieε deεcribed below. To further inveεtigate the mechaniεm of action of compounds like NPS R-568 on the parathyroid cell Ca 2+ 3 receptor, binding studies using H-NPS R-568 can be performed. The specific binding of 3H-NPS R-568 to intact parathyroid cells or to membraneε prepared from parathyroid cellε is initially investigated by techniques well-known in the art. The kinetic parameters of binding will then be measured as a function of extracellular Ca 2+ concentrations. Specifically, Scatchard analysiε of the data will reveal the number of binding εiteε and the apparent affinity of the receptor εite for 3H-NPS R-568. Theεe parameterε will then be inveεtigated aε a function of changeε in the level of extracellular Ca 2+ in the buffer uεed for the aεεay. If model 1 is correct, then a significant level of εpecific binding εhould occur in the abεence of extracellular Ca 2+. Large changeε in the kinetic parameterε of binding aε a function of the level of extracellular Ca 2+ would favor model 2. It is expected that various other inorganic and organic polycations deεcribed above in other exampleε will cauεe •a εimilar changeε in the binding parameterε of H-NPS R-568 as does extracellular Ca 2+. This would support the view that these polycationε act at the extracellular Ca 2+-binding site, which is distinct from that to which compound like NPS R-568 bind. Example 21: Preparation of NPS 467 In a 250 ml round bottom flask, 10.0 g (100 mmoles) 3 '-methoxy acetophenone and 13.5 g (100 mmoles) 3-phenylpropylamine were mixed and treated with 125 mmoles (35.5 g) titanium(IV) isopropoxide. The reaction mixture was stirred 30 minutes at room temperature under a nitrogen atmosphere. After this time 6.3 g (100 mmoles) εodiu cyanoborohydride in 100 ml ethanol was added dropwise over the course of 2 minutes. The reaction was stirred room temperature under nitrogen for 16 hours. After thiε time the reaction mixture waε tranεferred to a 2 L separator funnel with 1.5 L ethyl ether and 0.5 L water. The phases were equilibrated and the ether layer removed. The remaining aqueous phaεe waε thoroughly extracted with four 1 L portionε of ether. The washes were combined, dried over anhydrous potasεium carbonate and reduced to a clear, light amber oil. TLC analyεiε of this material on εilica uεing chloroform-methanol-isopropylamine (100:5:1) showed product at R f 0.65 with traces of the two starting materials at R f 0.99 (3 '-methoxy acetophenone) and Rr 0.0 (3-phenylpropylamine) . The reaction mixture was chromatographed through silica (48 x 4.6 cm) using a gradient of chloroform- methanol-iεopropylamine (99:1:0.1) to (90:10:0.1) which yielded 13.66 g of purified NPS 467. Thiε material waε disεolved in hexane-iεopropanol (99:1) containing 0.1% diethylamine to yield a εolution with a concentration of 50 mg/ml. Chiral reεolution was accomplished by chroma tography of 4 ml of this solution (200 mg, maximum to achieve separation) through ChiralCel OD (25 x 2 cm) using 0.7% isopropylamine, 0.07% diethylamine in hexane at 100 ml/min, monitoring optical density at 260 nm. Under these conditions (with injectionε of 100 mg material) the early-eluting isomer (NPS 467R) began to emerge from the column at a26 min, the late eluting isomer (NPS 467S) began to emerge at 34 minutes. Baseline resolution was accomplished under these conditions. Each optical isomer (free base) was converted to the corresponding hydrochloride salt by diεεolving 3 g of the free baεe in 100 ml ethanol and treating with it with 100 ml water containing 10 molar equivalents HCl. Lyophilization of this solution yielded a white solid. NPS 568 NPS 568 is a structural analog of NPS 467 that is more potent in causing increaseε in [Ca + ]. in bovine and human parathyroid cellε. Like NPS 467, the effectε of NPS 568 are εtereoεpecific and it iε the R-iεomer that is the more potent enantiomer (see Table 6, supra) . NPS R-568 iε at present the lead calcimimetic compound with selective activity at the parathyroid cell Ca 2+ receptor. It behaves, albeit with greater potency, similarly to NPS R-467 as described in Examples above. Thus, NPS R- 568 evokes increases in [Ca 2+]. m bovine parathyroid cells in a stereospecific manner (see Table 6, supra) . NPS R-568 fails to evoke increases in [Ca 2+]. in the absence of extracellular Ca 2+ but it does potentiate responses to extracellular Ca 2+ . NPS R-568 shiftε the concentration-reεponεe curve for extracellular Ca 2+ to the left. The oral administration of NPS R-568 to rats causeε a doεe-dependent decreaεe in the levelε of εerum Ca 2+ (ED 50 = 7mg/kg) . The hypocalcemic response elicited by the oral administration of NPS R-568 is rapid in onset and iε paralleled by decreases in the levels of serum PTH. The hypocalcemic response evoked by the oral administration of NPS R-568 iε only marginally affected by prior complete nephrectomy. However, NPS R-568 failε to elicit a hypocalcemic responεe in parathyroidectomized ratε. NPS R-568 can thuε target εelectively the parathyroid cell Ca 2+ receptor in vivo and cause an inhibition of PTH secretion. The decreases in serum levels PTH together with the resulting hypocalcemia are desirable therapeutic effectε in cases of hyperparathyroidism. The syntheεiε of NPS R-568 is provided below. Example 22: Preparation of NPS 568 NPS 568 was prepared using the methods described in Example 21 substituting an equivalent amount of 3-(2- chlorophenyl)propylamine for 3-phenylpropylamine. It was found that allowing the mixture of 3'- methoxyacetophenone, 3-(2-chlorophenyl)propylamine and titanium(IV) isopropoxide to stir for 5 hours prior to treatment with NaCNBH 3 /EtOH resulted in εignificantly greater yield (98%). Example 23: NPS 467 Lowers Serum Ionized Calcium When Administered Orally Rats (male, Sprague-Dawley, 250-300 g) were fed standard rat chow and fasted overnight prior to the experiment. NPS R-467 waε εuεpended in corn oil and adminiεtered as a εingle oral doεe through a gavage needle. Three hours later a sample of blood waε taken from the tail vein and aεεeεsed for ionized Ca 2+ levels. Fig. 44 shows that NPS R-467 caused a dose-dependent reduction in serum levelε of ionized Ca 2+ when adminiεtered orally. Example 24 BOPCAR1 Cloning Method 1 An expreεεion cloning εtrategy uεing Xenopuε laeviε oocyteε waε used to identify the cDNA encoding the bovine parathyroid calcium receptor. Theεe techniqueε are deεcribed only briefly here, and a more complete description preceded this one in the sectionε describing techniques which may be used to clone additional forms of the Ca 2+-receptor from other cell types. Poly(A )-enriched RNA was initially prepared from bovine parathyroid glands using extraction with guanidinium thiocyanate, centrifugation through CsCl and oligo(dT) cellulose chromatography. Injection of the resultant poly(A )-enriched RNA into oocytes (25-50 ng/oocyte) conferred sensitivity to elevated extracellular concentrations of Ca 2+ and the trivalent cation (l-100μM) Gd 3+ as deεcribed herein, such that the two cations elicited calcium activated chloride currentε. No εuch currentε were elicited in control eggε injected with water. X. laevis frogs were selected on the basiε of their harveεted oocyteε exhibiting: (i) a high level of maturity (i.e., Stage V, VI); (ii) a high activity of Cl — currents activated by Ca2+ ionophores like A23187; (iii) a high level of functional expreεsion of Gd 3+-induced Cl—current when injected with 25 ng/oocyte of total poly(A) RNA isolated from bovine parathyroid. The mRNA was then subjected to size fractionation, utilizing preparative, continuous flow agarose gel electrophoresiε (Hediger, M.A. , Anal ■ Biochem. 159:280-286 (1986)) to obtain fractionε of poly(A )-RNA further enriched in tranεcriptε coding for the Ca 2+-receptor. A peak of activity (e.g., oocyteε injected with mRNA from theεe fractionε εhowed enhanced expreεεion of Gd 3+-acti.vated Cl—currentε obtained with a εize range of 4-5.5 kb. Thiε RNA was used to prepare a size-selected, directional cDNA library in the plasmid pSPORTl that was enriched in full length transcriptε. Senεe complementary RNA (cRNA) was then synthesized from the DNA insertε pooled from 350-500 independent cloneε from thiε library and injected into oocyteε. Gd 3+-activated Cl—currentε were obεerved following injection of RNA from a εingle filter containing 350 colonies. Preparation and injection of cRNA from succeεεively smaller pools of clones led to isolation of a single clone (BoPCaR 1) with a cDNA insert of 5.3 kb which expressed greatly enhanced Ca 2+-receptor acti.vi.ty following injection of its cRNA into oocytes. A plasmid containing the BoPCaR 1 cRNA (See plasmid, Figure 45; reεtriction map, Figure 46; and partial nucleotide εequence, Figure 47) has been deposited in the ATCC under deposit number ATCC 75416. The BoPCaR 1 cDNA is outside the size range of the size-εelected RNA found to expreεs neomycin elicited Cl channel activity in Xenopus oocytes. This iε consistent with the possibility that different isoforms or multiple genes may conceal other numbers of the Ca 2+ receptor gene family. Several pharmacological and biochemical criteria were uεed to identify thiε clone as encoding a bona fide bovine parathyroid Ca 2+-receptor. Oocyteε expressing the cloned receptor, but not water-injected oocytes, responded to increasing concentrations of extracellular Ca 2+ (1.5-5 mM) or Gd 3+ (20-600μM) with large increaseε m Cl— currentε (up to at leaεt 1.8 microampereε) that were several _ fold larger than those observed m poly(A )-mjected oocytes. These responεeε increased markedly over a period of one (1) to four (4) days after injection of the eggε with cRNA prepared from the BoPCaR 1 cDNA. Furthermore, the ranges of the concentrationε of the two cations eliciting this responεe were very εimilar to thoεe shown previously to act on bovine parathyroid cells m. vitroN eomycin (20-100 μM) , which is known to mimic cloεely the effects of Ca 2+ on parathyroi•d cells, produced changes m Cl- current in oocyteε essentially identical to those produced by Ca 2+ or Gd3+, and these occurred over the same range of concentrations over which thiε antibiotic moculates parathyroid SUBSTITUTE SHEET ISA/EP function in vitro. Finally, m vitro translation of RNA prepared from the clone resulted in a single major protein on polyacrylamide gels with a molecular weight of about 100 kd, whose synthesis was enhanced by inclusion of dog pancreatic microsomes, concomitant with an increase in apparent molecular weight of 10-15%. The latter suggests that the cloned receptor interacts strongly with membranes, as might be expected of an integral membrane protein receptor, and is glycosylated in itε native form. Studieε with the lectin concanaval A indicate that the Ca 2+-receptor iε likely a glycoprotein. Thuε, the pharmacological propertieε of the cloned receptor, which iε expreεsed at high levels in oocytes, as well as the biochemical studies carried out to date are completely consistent with its identity with the bovine parathyroid Ca 2+ dynamicε (as exemplified by changes in Ca 2+-activated Cl ~ currents in oocytes). Diagnostic"Use NPS R-568 or other compounds active on a calcium receptor can be used as a diagnostic tool. Specifically, a pharmaceutical preparation of such compounds is .useful as a diagnostic tool. In one example, a pharmaceutical preparation containing a para thyroid cell calcimimetic compound εuch aε NPS R-568 can be given by oral or another route of administration to hypercalcemiσ patients with symptomε of mental depreεεion. If theεe symptoms arise from an underlying hyperparathyroid state, such as primary hyper parathyroidism, then administration of NPS R-568 or a compound that acts similarly will alleviate those symptoms. If the symptoms do not abate, then the mental depression results from some pathological state that is not hyperparathyroidism. Thus, parathyroid cell calcimimetic compounds can be used in the differential diagnosiε of mental depression. Symptomε and εigns common to hyperparathyroidism and other disorders can also be differentially diagnosed in the manner described above. Such shared signs and symptoms include, but are not limited to, hypertension, muεcular weakness, and a general feeling of malaise. Alleviation of these εymptomε following treatment with a parathyroid cell Ca 2+ receptor calcimimetic compound would indicate that the problemε reεult from the underlying hyperparathyroidism. In another example, a compound acting as an antagonist (calcilytic) at the C-cell Ca 2+ receptor can be administered as described above to diagnose medullary thyroid carcinoma. In this case, administration of the C-cell Ca 2+ receptor calcilytic compound will depress serum levels of calcitonin which can be readily measured by radioimmunoasεay. Certain symptoms, aεεociated with medullary thyroid carcinoma, εuch aε diarrhea, may also be monitored to determine if they are abated or lessened following administration of the calcilytic compound. In a third example, a compound acting aε a calcimimetic at the juxtaglomerular cell Ca 2+ receptor can be used in the differential diagnosis of hypertension. In thiε caεe, adminiεtration of the juxtaglomerular cell Ca2+ receptor calcimimetic compound can be adminiεtered aε deεcribed above. A decreaεe in blood preεεure to normal levelε will occur if the hypertenεion reεultε mostly or exclusively from elevated levelε of renin rather than from an alternative pathological state. In another example, a compound acting as a εpecific calcimimetic on the osteoclast Ca 2+ receptor can be used in the differential diagnoεiε of high- and low- turnover formε of osteoporosis. In this case, such a compound can be administered in a suitable pharmaceutical preparation and the levels of serum alkaline phosphataεe, oεteocalcin, pyridinoline and/or deoxypyridinoline croεslinks, and/or some other predictive marker of bone resorption and/or formation measured by techniques well known in the art. A large decrease in one or more of these parameters would be predictive of high-turnover osteoporoεis, whereas a small or no decrease in these parameters would be predictive of low-turnover osteoporoεiε. Such information would dictate the appropriate treatment. Antireεorptive drugε would not be the appropriate sole therapy for low-turnover oεteoporoεiε. Theεe examples are not exhaustive but εerve to llluεtrate that εpecific Ca 2+ receptorε can be targeted with pharmaceutical preparationε and that the obεerved effectε of εuch preparationε on bodily functions and/or chemical constituents can be used diagnostically. In general, calcimimetic and calcilytic compounds that act on Ca 2+ receptors of the various cells described above can be used in the diagnosis of the various diεeases associated with the particular cell type. These diseases include but are not limited to bone and mineral-related disorders (as described in Coe et al. , Disorders of Bone and Mineral Metabolism, Raven Presε, 1990), kidney diεeases, endocrine diseases, cancer, cardiovascular diseaseε, neurological diεeaεes, gastrointeεtinal diεeases, and diseases associated with gestation. Examples of human.diεeaεeε or diεorders in which such molecules may be therapeutically effective are as follows: (1) a calcimimetic is expected to ameliorate psoriaεis by reducing the proliferation of the abnormal skin cells. (2) Since Ca 2++ blocks the effect of vasopreεεin on MTAL and cortical collecting cellε, a calcimimetic iε expected to reduce water retention in εtateε of vaεoprsssin exceεε, such as the syndrome of inappropriate vasopreεεin (ADH) εecretion. Converεely, calcium receptor antagoniεts used in εtateε of ADH deficiency are expected to potentiate the action of any ADH preεent, εuch aε in partial central diabeteε inεipidus. (3) Calcimimetics may be uεed to treat hypertenεion by (a) reducing renin εecretion, (b) by εtimulating production of vaεodilatorε εuch as PTHrP (PTH-related peptide) by vascular smooth muscle. (4) Calcimimetics are expected to increase platelet aggregability, which may be useful when platelet counts are low. Conversely, calcilytics are expected to inhibit platelet function in states where there is hypercoagulability. (5) Calcium promotes differentiation of colon and mammary cells. A calcimimetic is expected to reduce the risk of colon or breast cancer. (6) Calcium promotes urinary calcium excretion in the MTAL. A calcimimetic is expected to have a useful hypocalcemic action in the therapy of hypercalcemic disorders. The inhibitory effect of calcimimetics on osteoclasts and their stimulation of the secretion of the hypocalcemic peptide calcitonin make them expected to be useful in the therapy of hypercalcemia and its symptoms. A calcimimetic may also improve hypocalcemic symptoms by activating calcium receptors. Conversely, calcilytic is expected to reduce urinary calcium excretion and be useful in the treatment of kidney εtones. In addition, calcium suppresseε the formation of 1,25-dihydroxyvitamin D in the proximal renal tubule, and thiε vitamin D metabolite iε frequently overproduced in renal εtone patientε and contributeε to their hypercalciuria. Supreεsion of 1,25-dihydroxyvitamin D formation by a calcimimetic is expected to be useful treating renal calcium stone disease. (7) Endogenous amines could reproduce the εymptomε in uremic patientε by calcimimetic or lytic actionε. Calcimimetic and/or calcilytic agents are expected to improve these symptoms. (8) Some of the renal toxicity of aminoglycoside antibiotics may be mediated by interaction of these drugs with renal calcium receptors. Having the calcium receptor iε expected to make it poεεible to carry out drug εcreening easily when designing new drugs of these classes to minimize renal toxicity. In addition, a renal calcium receptor antagonist would prevent or treat this renal toxicity if it is related to this mechanism. (9) Some of the genetic component of calcium related disorders, such as osteoporosis, renal εtones, and hypertension are expected to be related to inherited problems with certain forms of the receptor. These now can be studied and genetic screening/testing carried out using receptor-based reagents. The human diseaεe, familial hypocalciuric hypercalcemia, may be due to a calcium receptor defect. Definitive diagnoεtic εeparation from caεeε of promary hyperparathyroidism could be carried out with receptor-based technology. (10) Calcium receptorε are preεent in the placenta and are expected to impact on diεorderε of placental function and tranεfer of nutrients to the growing fetus. Other embodiments are within the following claimε. We Claim: 8907V SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: Nemeth, Edward F. (ii) TITLE OF INVENTION: CALCIUM RECEPTOR-AC IVE MOLECULES (iii) NUMBER OF SEQUENCES: 1 (iv) CORRESPONDENCE ADDRESS: Wolf, Greenfield & Sacks, P.C 600 Atlantic Avenue Boston Massachusetts United States of America 02210-2204 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Diskette, 5.25 inch (B) COMPUTER: IBM-compatible (C) OPERATING SYSTEM: MS:DOS Version 3.3 (D) SOFTWARE: WordPerfect 5.1 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: Not Available (B) FILING DATE: Filed Herewith (C) CLASSIFICATION: Not Available (viii) ATTORNEY/AGENT INFORMATION: (A) NAME: Gates, Edward R. (B) REGISTRATION NUMBER: 31,616 (C) REFERENCE/DOCKET NUMBER: B0801/7012 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: (617) 720-3500 (B) TELEFAX: (617) 720-2441 (C) TELEX: EZEKIEL (2) INFORMATION FOR SEQ ID NO: 1: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 2148 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA to mRNA (iii) HYPOTHETICAL: No (iv) ANTI-SENSE: No (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 1: CCACGCGTCC GCGGAAAAAA AAAAAAAGTT CCCCACTCTA 40 GTACAGAGAA GGTTGGCAGA GTCGTAAGCC CCCAACCTCT 80 TAAACTTCTC TGCATCTCCA AGGAGAAGGA GGGAAGAGGG 120 GTTCTTTCCG ACCTGAGGAG CTGGATCTGG GGTCCGAGAA 160 CCCCAAGGTA GCACCGGAAA GAACAGCACA GGAGGCGAGA 200 GCGTGCGGTG GCCGGTKGGC GGGAGAACCA GACCCGACKY 240 CGCGGTCCTC GGYGCTGCCG GGKYCCSGGG ACTCAGCTCA 280 GCACGACTGG GAAGCCGAAA GTACTACACA CGGTCTCTGC 320 ATGATGTGAC TTCTGAAGAC TCAAGAGCCA CCCACTTCAC 360 TAGTCTGCAA TGGAGAAGGC AGAAATGGAA AGTCAAACCC 400 CACGGTTCCA TTCTATTAAT TCTGTAGACA TGTGCCCCCA 440 CTGCAGGGAG TGAGTCGCAC CAAGGGGGAA AGTCCTCAGG 480 GGCCCCCAGA CCACCAGCGC TTGAGTCCCT CTTCCTGGAG 520 AGAAAGCAGA ACTATGGCAC TTTATAGCTG CTGTTGGATC 560 CTCTTGGCTT TTTTCTACCT GGTGCACTTC CGCCTATGGG 600 CCTGACCAGC GAGCCCAAAA GAAAGGGGAC ATTATCCTCG 640 GGGGGCTCTT TCCTATTCAT TTTGGGGTTG MMGTGAAAGA 680 TCAGGATCTA AAGTCGAGGC CGGAGTCCGT GGAGTGTATC 720 AGGTATAATT TCCGAGGATT TCGCTGGTTA CAAGCTATGA 760 TATTTGCCAT AGAGGAAATA AACAGCAGTC CAGCCCTTCT 800 TCCCAACATG ACCCTGGGAT ACAGGATATT CGACACTTGT 840 AACACCGTCT CTAAAGCCTT GGAGGCCACC CTGAGTTTTG 880 TGGCCCAGAA CAAAATTGAC TCTTTGAACC TTGATGAGTT 920 CTGCAACTGC TCAGAGCACA TCCCCTCTAC CATCGCAGTG 960 GTGGGAGCTA CTGGCTCGGG CATCTCCACA GCAGTGGCCA 1000 ACCTGCTGGG GCTCTTCTAC ATCCCCCAGG TCAGCTATGC 1040 CTCCTCCAGC AGACTCCTCA GCAACAAGAA TCAATTCAAG 1080 TCCTTCCTCC GCACCATACC CAATGATGAA CACCAGGCCA 1120 CGGCCATGGC TGACATCATC GAGTACTTCC GCTGGAACTG 1160 GGTGGGCACA ATTGCAGCTG ACGATGACTA TGGCCGGCCA 1200 GGGATCGAGA AGTTTCGAGA GGAAGCTGAG GAGAGGGACA 1240 TCTGCATCGA CTTCAGCGAG CTCATCTCCC AATACTCTGA 1280 TGAGGAAAAG ATCCAGCAGG TGGTGGAGGT GATCCAGAAT 1320 TCCACCGCCA AAGTCATTGT CCGTCTTCTC CAGCGGCCCA 1360 GACCTGGAAC CCCTCATCAA AGAGATCGTC CGGCGCAATA 1400 TCACAGGCAG GATCTGGCTG GCCAGCGAGS CTGGSCAGCT 1440 CTTCCCTGAT TGCTATGCCC GAGTATTTCC ATGTGGTCGG 1480 AGGCACCATT GGGTTTGGTT TGAAAGCTGG GCAGATCCCA 1520 GGCTTCCGGG AATTCCTGCA GAAAGTCCAC CCCAGGAAGT 1560 CTGTCCACAA TGGTTTTGCC AAGGAGTTTT GGGAAGAAAC 1600 ATTTAACTGC CACCTGCAAG AGGGTGCTAA AGGCCCATTA 1640 CCGGTGGACA CCTTCCTGAG AGGTCACGAA GAAGGAGGTG 1680 CCAGGTTAAG CAACAGTCCC ACTGCCTTCC GACCTCTGTG 1720 CACTGGGGAG GAGAACATCA GCAGTGTCGA GACTCCTTAC 1760 ATGGATTATA CACATTTACG GATATCCTAC AACGTCTACT 1800 TAGCCGTCTA CTCCATTGCT CATGCCCTAC AAGATATATA 1840 CACCTGCATA CCTGGGAGAG GGCTCTTCAC CAACGGTTCC 1880 TGCGCAGATA TCAAGAAGGT TGAAGCTTGG CAGGTCCTGA 1920 AACACCTGCG GCACCTAAAT TTTACCAGCA ATATGGGGGA 1960 GCAAGTAACT TTCGATGAAT GTGGAGACCT GGCAGGGAAC 2000 TATTCCATCA TCAACTGGCA CCTCTCCCCA GAGGACGGCT 2040 CCATAGTGTT TAAGGAAGTT GGATATTACA ATGTCTATGC 2080 CAAGAAAGGA GAGAGACTCT TCATCAATGA TGAAAAAATT 2120 CTGTGGAGTG GATTCTCAAG GGAGGTGC 2148 8907V

Claims: Claim: 1. A pharmaceutical composition comprising a r.olecule which mimics the activity of extracellular C :* by evoking an increase in [Ca 2 *]i in a cell, cr Ξ blocks an increase in [C 2* ]i evoked by extracellular Ca : \ said molecule having an EC 50 of less than or equal cc 5 μM, wherein said molecule is not protamine. 2. The pharmaceutical composition of claim 1 wherein said increase in [Ca 2 *]i in a cell is transient, 0 having a duration of less than thirty seconds. 3. The pharmaceutical composition of claim 1 cr 2 wherein said increase in [Ca 2 *]i is rapid, occurring within thirty seconds. 4. The pharmaceutical composition of claim 1 wherein said molecule evokes a sustained increase in [C 2* ]i, having a duration greater than thirty seconds. 5. The pharmaceutical composition of claim 1 wherein said molecule further evokes an increase in inositol-1, 4 , 5-trisphosphate or diacylglycerol . 6. The pharmaceutical composition of claim 5 wherein said increase in said inositol-1, , 5- crisphosphate or diacylglycerol occurs within 60 seconds . 7. The pharmaceu ical composition of claim 2 wherein said transient increase is diminished by pretreatment of said cell for less than 10 minutes with an activator of protein kinase C. 8. The pharmaceutical composition c claim 7 wherein said activator of protein kinase C is selected frcir. che group consisting of phorbol rrryristace acetate, mezerein and (-)-indolactam V. 9. The pharmaceutical composition of claim 1 wherein said molecule inhibits άopamine- or isoproterenol-stimulated cyclic AMP formation. 10. The pharmaceutical composition of claim 2 wherein said transient increase in [Ca 2* ]j . is reduced by pretreatment of said cell for ten minutes with 10 mM sodium fluoride. 11. The pharmaceutical composition cf claim 1 wherein said cell is a parathyroid cell and said molecule inhibits parathyroid hormone secretion from said cell. 12. The pharmaceutical composition of claim 1 wherein said molecule elicits an increase in Cl " conductance in a Xenopus oocyte injected with mRNA from a cell selected from the group consisting of parathyroid cells, bone osteoclasts, juxtaglomerular kidney cells, proximal tubule kidney cells, keratinocytes, perifollicular thyroid cells and placental trophoblasts. 13. The pharmaceutical composition cf claim 1 wherein said molecule mobilizes intracellular Ca 2 " to cause said increase in [Ca 2* ]^ 14. The pharmaceutical composition cf claim 1 wherein said cell is a C-cell or an osteoclast and said molecule inhibits bone resorption i vivo. 15. The pharmaceutical composition of claim 1 wherein said cell is a C-cell and said molecule stimulates calcitonin secretion in vitro or in vivo. 16. The pharmaceutical composition of claim 1 wherein said molecule is either a calcimimetic or calcilytic having an EC £0 or IC S0 at a Ca 2 " receptor of less than or equal to 5 μM. 17. The pharmaceutical composition of claim 1 wherein said molecule has an EC S0 less than or equal to 5 μM at one or more but not all cells chosen from the group consisting of parathyroid cells, bone osteoclasts, juxtaglomerular kidney cells, proximal tubule kidney cells, keratinocytes, perifollicular thyroid cells and placental trophoblasts. 18. The pharmaceutical composition of claim 1 or 16 or 17 wherein said molecule has an EC 50 or IC 50 less than or equal to 1 μM. 19. The pharmaceutical composition of claim 1 or 16, or 17 wherein said molecule has an EC 50 or IC S0 less than or equal to 100 nanomolar. 20. The pharmaceutical composition of claim 1 or 16, or 17 wherein said molecule has an EC 50 or IC S0 less than or equal to 10 nanomolar. 21. The pharmaceutical composition of claim 1 or 16, wherein said molecule has an EC 50 or IC 50 less than or equal to 1 nanomolar. 22. The pharmaceutical composition of claim 1, 16 or 17 wherein said molecule is positively charged at physiological pH. 23. The pharmaceutical composition of claim 22 wherein said molecule is selected from the group consisting of branched or cyclic polyamines, positively charged polyamino acids, and arylalkylamines. - I SO - 24. The pharmaceutical composition of claim 23 wherein said branched polyamine has the formula H 2 N-(CH 2 ) ( Ri-(CH 2 ) ) k -NH 2 wherein k is an integer from 1 to 10, each j is the same or different and is an integer from 2 to 20, and each Ri is the same or different and is selected from the group consisting of hydrogen and -(CH 2 )j-NH 2 , wherein j is as defined above, and wherein at least one R< is not hydrogen. 25. The pharmaceutical composition of claim 1, 16 or 17 wherein said molecule has the formula wherein each X is selected (independently) from the group consisting of H, CH 3 , CH 3 0, CH 3 CH 2 0, Br, Cl, F, CF 3 , CHF 2 , CH 2 F, CF 3 0, CH 3 S, OH, CH 2 OH, CONH 2 , CN-, N0 2 , and CH 3 CH 2 ; Ar is a hydrophobic entity; each R independently is selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, indenyl, indanyl, dihydroindolyl, thiodihydroindolyl, and 2-,3-, or 4- piperid(in)yl; Y is selected from the group consisting of CH, nitrogen and an unsaturated carbon; Z is selected from the group consisting cf oxygen, nitrogen, sulfur, where each n is independently between 1 and 4 inclusive, and each m is independently between 0 and Ξ inclusive; wherein said molecule is either a calcimimetic or calcilytic. 26. The pharmaceutical composition of claim 25 wherein said hydrophobic entity is selected from the group consisting of phenyl, 2-, 3-, or 4-pyridyl, 1- or 2-naphthyl, 1- or 2-quinolinyl, 2- or 3-indolyl, benzyl, and phenoxy. 27. A pharmaceutical composition comprising a molecule having the formula wherein each X independently is selected from the group consisting of H, CH 3 , CH 3 0, CH,CH 2 0, Br, Cl, F, CF 3 , CHF 2 , CK 2 F, CF 3 0, CH 3 S, OH, CH 2 OH, CONH 2 , CN, N0 2 , and CK 3 CK 2 ; Ar is a hydrophobic entity; each R independently is selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, indenyl, indanyl, cihydroindolyl, thiodihydroindolyl, and 2-,3-, or 4- piperid(in)yi; Y is selected from the group consisting of CH, nitrogen and an unsaturated carbon; Z is selected from the group consisting of oxygen, nitrogen sulfur, X X where each n is independently between 1 and 4 inclusive, and each is independently between 0 and 5 inclusive; - 1S2 - wherein said molecule is not NPS 447 cr NPS 449. 28. The pharmaceutical composition cf claim 27 wherein said molecule is NPS 467. 29. The pharmaceutical composition of claim 25 wherein said molecule is NPS 459, NPS 467, or NPS 568. 30. The pharmaceutical composition of claim 25, wherein said molecule is an R-phenylpropyl-α-phenet- hylamine derivative. 31. The pharmaceutical composition of claim 27, wherein said molecule is an R-phenylpropyl-α-phenet- hylamine derivative. 32. The pharmaceutical composition of claim 30 wherein said molecule has the formula: 33. The pharmaceutical composition of claim il wherein said molecule has the formula: 34. The pharmaceutical composition of claim 32 wherein each X is independently selected frc the croup consisting of Cl, F, CF 3 , CH 3 , and CH 3 0. 35. The pharmaceutical composition of claim 33 wherein each X is independently selected from the group consisting of Cl, F, CF 3 , CH 3 , and CH 3 0. 36. A method for treating a patient having a disease characterized by an abnormal [Ca 2* ] or [Ca 2* .j, in one or more cells or in the blood or plasma, comprising the step of administering to said patient a therapeutically effective amount of a molecule which mimics the activity of extracellular Ca 2* by evoking an increase in [Ca*]i in a cell, or blocks an increase in [Ca 2* ]. evoked by extracellular Ca 2* . 37. The method of claim 36 wherein said molecule has an EC 50 of less than or equal or 5 μM. 38. The method of claim 36 wherein said molecule is not protamine. 39. The method of claim 36 wherein said molecule interacts at a Ca 2 * receptor as a calcimimetic cr calcilytic. 40. The method of claim 36 wherein said increase in [C 2+ ]i in a cell is transient, having a duration of less than thirty seconds. 41. The method of claim 36 or 40 wherein said increase in [Ca 2 *^ is rapid, occurring within thirty seconds. 42. The method of claim 36 wherein said molecule evokes a sustained increase in (Ca 2 "]^ having a duration greater than thirty seconds. 43. The method of claim 36 wherein said molecule further evokes an increase in inositol-1, ,5- trisphosphate or diacylglycerol. 44. The method of claim 43 wherein said increase in said inositol-1, ,5-trisphosphate or diacylglycerol occurs within less than 60 seconds. 45. The method of claim 40 wherein said transient increase is diminished by pretreatment of said cell with an activator of protein kinase C. 46. The method of claim 45 wherein said activator of, protein kinase C is selected from the group consisting of phorbol myristate acetate, mezerein and (-)-indolacta V. 47. The method of claim 36 wherein said molecule inhibits dopa ine- or isoproterenol-stimulated cyclic AMP formation. 48. The method of claim 40 wherein said transient increase in [Ca 2* ]; is reduced by pretreatment of said cell for ten minutes with 10 mM sodium fluoride. 49. The method of claim 36 wherein said cell is a parathyroid cell and said molecule inhibits parathyroid hormone secretion from said cell. 50. The method of claim 36 wherein said molecule elicits an increase in Cl " conductance in a Xenopus oocyte injected with mRNA from a cell selected from the group consisting of parathyroid cells, bone osteoclasts, juxtaglomerular kidney cells, proximal tubule kidney cells, keratinocytes, perifollicular thyroid cells and placental trophoblasts. 51. The method of claim 36 wherein said molecule mobilizes Ca 2 * within the cell to cause said increase in [Ca*]i. 52. The method of claim 36 wherein said cell is a C-cell or an osteoclast and said molecule inhibits bone resorption in vivo. 53. The method of claim 36 wherein said cell is a C-cell and said molecule stimulates calcitonin secretion in vitro or in vivo. 54. The method of claim 36 wherein said molecule is either a calcimimetic or calcilytic having an ΞCC Q or IC 50 at a Ca 2 * receptor of less than or equal to 5 μM. 55. The method of claim 36 wherein said molecule has an EC 50 less than or equal,to 5 UM at one or more but not all cells chosen from the group consisting of parathyroid cells, bone osteoclasts, juxtaglomerular kidney cells, proximal tubule kidney cells, keratinocytes, perifollicular thyroid cells and placental trophoblasts. 56. The method of claim 36, 54 or 55 wherein said molecule has an EC 50 or IC S0 less than or equal to 1 μM. 57. The metho -of claim 36, 54 or 55 wherein said molecule has an EC 50 or IC S0 less than or equal to 100 nanomolar. 58. The method of claim 36, 54, or 55 wherein said molecule has an EC 50 or IC 50 less than or eσ al to 10 nanomolar. 59. The method of claim 38, Ξ cr 5Ξ, wherein said molecule has an EC 50 or IC 50 less than or equal to 1 nanomolar. 60. The method of claim 36, 54 or 55 wherein 5 said molecule is positively charged at physiological pH. 61. The method of claim 60 wherein said molecule is selected from the group consisting of branched or cyclic polyalkylamines, positively charged polyamino acids, and arylalkylamines. 10 62. The method of claim 61 wherein said branched polyamine has the formula H 2 N-(CHj) j -(NRi-(CH 2 ) d ) k -NH 2 wherein k is an integer from 1 to 10, each j is the same or different and is an integer 15 from 2 to 20, and each Ri is the same or different and is selected from the group consisting of hydrogen and -(CK 2 ) j -NH 2 , wherein j is as defined above, and wherein at least one R t is not hydrogen. 20 63. The method of claim 36, 54 or 55 wherein said molecule has the formula wherein each X independently is selected from the group consisting of H, CH 3 , CH 3 0, CH 3 CH 2 0, Er, Cl, F, CF 3 , CHF 2 , CH 2 F, CF 3 0, CH 3 S, OH, CH 2 OH, C0NH 2 , CN, N0 2 , and «_.- CH 3 CH 2 ; Ar is a hydrophobic entity; each R independently is selected frcm the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, indenyl, indanyl, dihydroindolyl, thiodihydroindolyl, and 2-,3-, or 4- piperid(in)yl; Y is selected from the group consisting of CH, nitrogen and an unsaturated carbon; Z is selected from the group consisting of oxygen, nitrogen, sulfur, where each n is independently between 1 and 4 inclusive, and each is independently between 0 and 5 inclusive; wherein said molecule is either a calcimimetic or calcilytic. 64. The method of claim 63.wherein said hydrophobic entity is selected from the group consisting of phenyl, 2- 3-, or 4-pyridyl, 1- or 2-naphthyl, 1- or 2-quinolinyl, 2 - or 3-indolyl, benzyl, and phenoxy. 65. The method of claim 36, 54 or 55 wherein said molecule has the formula wherein each X independently is selected from the group consisting of H, CH 3 , CH 3 0, CH 3 CH 2 0, Br, Cl, F, CF 3 , CHF 2 , CH 2 F, CF 3 0, CH 3 S, OH, CH 2 0H, CONH 2 , CN, N0 2 , and CH 3 CH 2 ; Ar is a hydrophobic entity; each R independently is selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, cyclopentyl, cyclchexyl, cycloheptyl, cyclooctyl, indenyl, inάanyl, cihydroindolyl, thio ihydroinάolyl, and 2-, -, or 4- piperid(in)yl; Y is selected from the group consisting of CH, nitrogen and an unsaturated carbon; Z is selected from the group consisting of oxygen, nitrogen, X or R X or R X X or R X or R X where each n is independently between 1 and 4 inclusive, and each m is independently between 0 and 5 inclusive; wherein said molecule is not NPS 447 or NPS 449. 66. The method of claim 65 wherein said molecule is NPS 467 or NPS 019. 67. The method of claim 63 wherein said molecule is NPS 467 and NPS 568. 68. The method of claim 63, wherein said molecule is an R-phenylpropyl-α-phenethylamine deriva- tive. 69. The method of claim 65, wherein said molecule is an R-phenylpropyl-α-phenethylamine derivative. 70. The method of claim 68 wherein said molecule has the formula: 71. The method of claim 69 wherein said molecule has the formula: 72 . The method of claim 70 wherein each X is independently selected from the group consisting of Cl , F , CF 3 , CH 3 , and CH 3 0. 73. The method of claim 71 wherein each X is independently selected from the group consisting of Cl, F, CF 3 , CH 3 , and CH 3 0. 74. The method of claim 36 wherein said patient has a disease characterized by an abnormal level of one or more ions or substances, the level of which is regulated or affected by activity of one or more Ca 2* receptors. 75. The method of claim 74, wherein said molecule is active on a Ca 2 * receptor of a cell selected from the group consisting of parathyroid cells, bone osteoclasts, juxtaglomerular kidney cells, proximal tubule kidney cells, keratinocytes, perifollicular thyroid cells, and placental trophoblasts. 76. The method -of claim 36, wherein said patient has a disease selected from the group consisting cf primary and secondary hyperparathyroidism, Paget's disease, hypercalcemia malignancy, osteoporosis and hypertension. . /0_<;4 2 - 190 - 77. The method cf claim 75 wherein said molecule is active only at one or more said Ca' * receptors and not all said Ca 2* receptors. 78. The method of claim 36 wherein said molecule reduces the level of parathyroid hormone in the serum of said patient. 79. The method of claim 78, wherein said level of parathyroid hormone is reduced to that level present in a normal individual. 80. The method of claim 78 wherein said level is reduced to a degree sufficient to cause a decrease in plasma Ca 2* . 81. The method of claim 78 wherein εaid molecule is provided in an amount sufficient to have a therapeutically relevant effect on said patient. 82. The method of claim 36 wherein said molecule blocks an increase in [Ca 2 *] within the cell evoked by extracellular [Ca 2* ]'. 83. A method for diagnosis of a disease cr condition in a patient, comprising the steps of identifying the number and/or location of one or more Ca 2* receptors within said patient and comparing said number and/or location with that observed in normal patients as an indication of the presence of a said disease or condition. 84. The method of claim 83 wherein said method is an immunoassay in which an antibody to a Ca 2* receptor is used to identify the number or location cf said Ca 2 * receptors. 85. The method cf claim 83 wherein said assay comprises providing a labeled calcimimetic or 2~- calcilytic molecule which binds to a Ca ' receptor. 86. The method of claim 83 wherein said disease is a cancer. 87. The method of claim 86 wherein said cancer is an ectopic tumor in the parathyroid. 88. The method of claim 83 wherein said condition is characterized by an increased number or activity of the osteoclasts in bone. 89. A method for treatment of ostioporosis , hyperparathyroidism or hypertension, comprising the εtepε of administering a therapeutically effective amount of a compound which mimics the activity of extracellular C ~a2+ by evoking an increase in [Ca 2+]. in a cell, or blockε an increaεe in 2+ 2+ [Ca ] . in the presence of extracellular Ca 90. A method for identifying a compound useful as a therapeutic agent, comprising the steps of screening a potentially useful molecule for its ability to mimic the activity of extracellular Ca 2+ in a cell, or to block an increase in [Ca 2+ ] • (elicited by extracellular Ca 2+), and determining whether said molecule has EC fl of less than or equal to 5 μM. 91. A reccmDinant _a2- receptor. 92. A ceil compri .si•ng a reccmDi.nant Ca 2- receptor. 93. A method for identifying a useful calcimimetic compound comprising the step of identifying a compound which mimicε one or more activities of Ca 2+ at a fi■rst Ca 2-- ' receptor but not at a second Ca 2+ receptor. 94. A method for identifying a useful calcilytic compound comprising the step of identifying a ccmpound which blocks one or more activities of 2~- . 2+ Ca at a first Ca receptor but not at a second receptor . 95. The method of claim 93 or 94 wherein said method includes providing a recombinant Ca 2+ receptor useful in said identifying step. 96. Purified nucleic aciα encoding a Ca 2~'- receptor. 97. The compounds NPS 459, NPS 467, NPS 544 and NPS 568 and pharmaceutically acceptable acid addition salts and complexes thereof. 98. The pharmaceutical composition of claim 25 wherein said molecule is NPS 447, NPS 448, NPS 449, NPS 456 c r NPS 55 1 . 99. A compound of the formul wherein alk is straight cr branched-chain alkylene cf from 1 to 6 carbon atoms; R. is lower alkyl of from 1 to 3 carbon atoms cr lower haloalky! of from 1 to 3 carbon atomε substituted with from 1 to 7 halogen 3 atoms; and R» and R are independently εelected monocyclic or bicyclic carbocyclic aryl or cycloalkyl groups, having 5- or 6-membered rings optionally substituted with 1 to 5 substituents independently selected from lower alkyl of 1 to 3 carbon atoms, lower haloalkyl of 1 to 3 carbon atoms substituted with 1 to 7 halogen atoms, lower alkoxy of 1 to 3 carbon atomε, halogen, nitro, amino, alkylamino, amido, lower alkyiamido of 1 to 3 carbon atomε, cyaπc, hydroxy, acyl of 2 to 4 carbon atoms or lower thioaikyl of 1 to 3 carbon atoms and pharmaceutically acceptable salts and acid addition salts thereof. 100. A compound according to claim 99 wherein alk is n-proovlene. 101. A compound according tc claim 100 wherein R. is methyl. 102. A compound according to claim 101 wherein R 2 and R are independently selected optionally substituted phenyl groupε. 103. A iεolated nucleic acid encoding an inorganic-ion receptor or a unique fragment thereof. 104. An isolated nucleic acid as claimed in claim 103 encoding a human inorganic-ion receptor or a unique fragment thereof. 105. An isolated nucleic acid as claimed in claim 103 encoding an inorganic-ion receptor that hybridizes to Sequence 1. 106. An isolated nucleic acid as claimed in claim 103 encoding an inorganic-ion receptor that hybridizes to BoPCaR 1 or a unique fragment thereof. 107. An isolated nucleic acid claimed in claim 103 encoding a calcium receptor or a unique fragment thereof. 108. An isolated nucleic acid as claimed in claim 107 encoding a calcium receptor that is expresεed' in tissues or ceils selected from the group consisting of: parathyroid, vascular, kidney, epidermis, thyroid, osteoclast, intestine, mammary, trophoblast platelet, gastrin εecreting, glucagon secreting, cardiac, and brain, and unique fragments thereof. 109. An isolated nucleic acid aε claimed in claim 103, wherein the nucleic acid is a fragment encoding the extracellular binding domain but substantially free of transmembrane and intracellular domain portions. 110. A iεolated nucleic acid as claimed in claim 103, wherein the nucleic acid is a fragment encoding the intracellular domain but εubstantially free of tranεmembrane and extracellular binding domains. 111. An isolated nucleic acid aε claimed in claim 109, wherein the fragment encoding the extracellular binding domain is transcriptually coupled to nucleic acid encoding transmembrane and intracellular coding domains of a noninorganic-ion receptor. 112. An isolated nucleic acid as claimed in claim 103, comprising BoPCaR 1 or a unique fragment thereof. 113. The isolated nucleic acid of any one cf claims 103, 104, 105, and 106 under the transcriptional control of an exogenous promoter. 114. A recombinant cell expressing the nucleic acic of any one of claims 103, 104, 105, 106 and 107. 115. An isolated inorganic-ion receptor, or a unique fragment thereof. 116. An isolated inorganic-ion receptor as claimed in claim 115 that is a human inorganic-ion receptor, or a unique fragment thereof. 117. An isolated inorganic-ion receptor as claimed in claim 115 or 116 wherein the receptor is a calcium receptor. 118. An isolated inorganic-ion receptor as claimed in claim 115 that is a calcium receptor expressed in tissues or cells εelected from the group consisting of: parathyroid, vascular, kidney, epidermis, thyroid, osteoclast, intestine, mammary, trophoblast platelet, gastrin secreting, glucagon εecreting, cardiac, and brain, and unique fragments thereof. 119. An isolated inorganic-ion receptor as claimed in claim 115 that is the expreεεion product of BoPCar 1, or a unique fragment thereof. 120. An isolated inorganic-ion receptor as claimed in claim 115 that is a human parathyroid calcium receptor or unique fragment thereof. 121. An isolated inorganic-ion receptor as claimed in claim 13 that is an extracellular, ion-bonding fragment substantially free of intracellular and transmembrane domains. 122. An iεolated inorganic-ion receptor as claimed in claim 111 that is a calcium-binding fragment. 123. Purified antibodies to an inorganic-ion receptor. 124. Purified antibodies as claimed in claim 123 to an extracellular domain of an inorganic-ion receptor. 125. Purified antibodies as claimed in claim 123 to a calcium receptor. 126. Purified antibodieε aε claimed in claim 125 to a calcium receptor expresεed in tissue or cells selected from the group consisting of: parathyroid, vascular, kidney, epidermis, thyroid, osteoclast, intestine, mammary, trophoblaεt platelet, gastrin εecreting, glucagon secreting, cardiac, and brain, and unique fragments thereof. 127. Purified antibodies as claimed in claim 124 to a calcium receptor. 128. Purified antibodies as claimed in claim 127 to an alloεteric εite of a calcium receptor. 129. Purified antibodies as claimed in claims 124, 125, 126 or 127 coupled to a toxin. 130. An inorganic-ion receptor binding agent coupled to a toxin. 131. An agent aε claimed in claim 131 wherein the agent selectively bindε a calcium receptor . 132. A tranεgenic, nonhuman mammal containing a transgene encoding an inorganic-ion receptor or a unique fragment thereof. 133. A tranεgenic mammal as claimed in claim 132 wherein the transgene encodes a calcium receptor or a unique fragment thereof. 134. A transgenic, nonhuman mammal containing a tranεgene that alters the expression of an inorganic-ion receptor. 135. A tranεgenic mammal aε claimed in claim 134 wherein the transgene inactivateε the expreεεion of the inorganic-ion receptor. 136. A tranεgenic mammal aε claimed in claim 134 wherein the tranεgene up-regulateε or down-regulates the expression of the inorganic-ion receptor. 137. A transgenic mammal as claimed in claims 134, 135 or 136 wherein the transgene alters the expression of a calcium receptor. 138. A method for identifying nucleic acid encoding an inorganic-ion receptor comprising contacting a library of nucleic acid with a probe selected from the group consisting of: (a) BoPCaR 1 (b) a unique fragment of BoPCaR 1 (c) the human homolog of BoPCaR 1 (d) a set of degenerate probeε of any of (a), (b) or (c) and identifying sequences within the library that hybridize to the probe. 139. A method as claimed in claim 138 further comprising isolating the nucleic acid encoding the inorganic-ion receptor. 140. A method aε claimed in claim 138 further comprising identifying a tiεεue in which the inorganic-ion receptor is expressed. 141. A method for modulating the expression of an inorganic-ion receptor comprising contacting a ceil with an agent that binds to a cellular component selected from the group consisting of: a promoter; a regulatory agent acting on a promoter; an agent capable of binding to the receptor; and a nucleic acid encoding the receptor or a unique fragment thereof. 142. A method as claimed in claim 141 wherein the cell is contacted with an antisense nucleic acid. 143. A method as claimed in claim 141 wherein the cell is contacted with a DNA constructed and arranged to combine through homologous recombination with an endogenous gene encoding the receptor and to inactivate expression of the receptor in the cell. 144. A method for killing a cell expresεing an inorganic-ion receptor compriεing contacting the cell with an agent capable of binding to the inorganic-ion receptor, wherein the agent is conjugated to a toxin. 145. A method for identifying an agent that is an agonist or an antagonist of an inorganic-ion receptor, comprising contacting a cell containing a recombinant nucleic acid encoding an inorganic-ion receptor with the agent and detecting a change in the cell. 146. A method for identifying an agent that binds to an inorganic-ion receptor comprising an asεay employing an isolated inorganic-ion receptor.

Inventors: BALANDRIN MANUEL F, BROWN EDWARD M, DEL MAR ERIC G, FULLER FORREST H, HEBERT STEVEN C, NEMETH EDWARD F, VAN WAGENEN BRADFORD C, BALANDRIN, MANUEL, F., BROWN, EDWARD, M., DEL MAR, ERIC, G., FULLER, FORREST, H., HEBERT, STEVEN, C., NEMETH, EDWARD, F., VAN WAGENEN, BRADFORD, C.
Applicants: BRIGHAM & WOMENS HOSPITAL, NPS PHARMA INC, BRIGHAM AND WOMEN'S HOSPITAL, INC., NPS PHARMACEUTICALS, INC.
Application year: 1993
Main classification: A61K31
IPC codes: A01K67, A61K31, A61K39, A61K45, A61K48, A61P3, A61P9, A61P43, C07K14, C12N15