bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular studies on kinin receptors
Authors: Brown Michael , Webb Michael , Phillips Elsa , Skidmore Elizabeth , McIntyre Peter
Published: April 2011

We describe the results of functional studies on DNA clones encoding functional bradykinin receptors derived from human, rat, and mouse sources and including both genomic and complementary DNA clones. In both the Xenopus oocyte and the COS cell expression systems, the receptors from human and rat showed the pharmacological properties of B2 receptors, but receptors from mouse displayed both B1- and B2-like pharmacological properties. We further investigated the molecular relationship between the B1 and B2 receptor subtypes expressed by a human fibroblast cell line, and we demonstrate that these two receptor subtypes are encoded by distinct mRNA species.Key words: B1 receptor, antisense, Xenopus oocyte.
Pharmacology of kinin receptors: recent developments
Authors: Regoli Domenico , Gobeil Fernand
Published: April 2011

Fifteen years after the classification of kinin receptors into B1 and B2, both receptors have been shown to differ between species. New receptor types have been proposed and named B3, B4, and B5. However, it is not established whether different pharmacologic profiles describing B2 receptors in various species are indicative of different receptor types or of different subtypes (species dependent) subserving the same biological functions. To answer these questions, a systematic search of new pharmacologic tools was undertaken to find monoreceptor systems (isolated organs whose responses are contributed by a single receptor) as well as new selective agonists and competitive or noncompetitive antagonists. Classical pharmacologic experiments were performed in isolated organs for quantifying agonist activities in terms of pD2 and antagonist affinities in terms of pA2. Competitivity of antagonists was established from Schild plots. Results obtained in tissues from rabbits or guinea pigs indicate the existence of two different pharmacological entities, well characterized by selective agonists and competitive antagonists. In vivo experiments performed on anesthetized rabbits and guinea pigs have confirmed the B2 receptor heterogeneity between the two species. Correlations have been established between data obtained in rabbit and guinea pig tissues (biological assays) and in human receptors raised by genic transfection in Chinese hamster ovary (CHO) cells. A good correlation has been found between the IC50 values of kinins and derivatives to displace [3H]bradykinin from the membranes of CHO cells containing the human receptor and the pD2 or pA2 values of the same compounds in the rabbit jugular vein.Key words: bradykinin, smooth muscle, receptors, antagonists.
Bradykinin as an endogenous myocardial protective substance with particular reference to ischemic preconditioning–a brief review of the evidence
Authors: Parratt James R. , Vegh Agnes , Papp Julius Gy.
Published: April 2011

The present brief review summarizes the evidence for the possibility that endogenously released bradykinin plays a major role in protecting the heart against the consequences of acute myocardial injury. This evidence includes the facts that kinins are generated under myocardial ischemia; that when they are administered, they are cardioprotective (e.g., antiarrhythmic); that drugs that enhance the release of bradykinin from the ischemic heart reduce the ischemic injury and, conversely, drugs that block bradykinin receptors attenuate the reduction in ischemic injury resulting from the release of, or administration of, bradykinin. The possible mechanism of bradykinin in the cardioprotection afforded by ischemic preconditioning is summarized. Ischemic preconditioning can be defined as the marked reduction in the severity of ischemic changes that result from coronary artery occlusion when that occlusion is preceded by brief periods of myocardial ischemia, either regional or global, induced, for example, by complete or partial coronary artery occlusion or by rapid ventricular pacing. The possible mechanisms of cardioprotection elicited by bradykinin (and ischemic preconditioning) are summarized. The most likely is the generation of cyclic GMP within the ischemic myocardium following bradykinin-stimulated nitric oxide generation and release from endothelial cells.Key words: endogenous myocardial protective substances, bradykinin, ischemic preconditioning, cardiac arrhythmias, myocardial ischemia.
Neurokinin receptors subserving airways secretion
Authors: Rogers Duncan F.
Published: April 2011

Mucus secretion can be induced in the airways by activation of nerves. The principal mechanism mediating neurogenic mucus secretion is cholinergic. However, a small but significant secretory response remains after adrenoceptor and cholinoceptor blockade. The identity of this nonadrenergic, noncholinergic (NANC) neural mechanism is unclear but includes an orthodromic pathway and a capsaicin-sensitive "sensory-efferent" (or "local effector") pathway. The orthodromic pathway comprises cholinergic nerves (and to a much lesser extent adrenergic nerves) in which neuropeptides, including vasoactive intestinal peptide (VIP) and neuropeptide tyrosine (NPY), are colocalised and coreleased with the classical neurotransmitter. Investigation of the contribution of the orthodromic neural pathway to neurogenic secretion awaits development of selective receptor antagonists for VIP and NPY. The neurotransmitters of the sensory-efferent neural pathway include calcitonin gene related peptide and the tachykinins substance P and neurokinin A. The order of potency of the natural tachykinins and synthetic selective tachykinin receptor agonists indicates that the tachykinin NK1receptor is ubiquitous for airway secretory processes, including mucus secretion and ion transport. Antagonist studies show that the great proportion of the NANC neural mucus secretory response is mediated via NK1receptors, with little or no contribution from NK2receptors. The relevance of the sensory-efferent neural pathway in health is equivocal, but it may have increasing importance in chronic inflammatory bronchial diseases associated with mucus hypersecretion, for example, asthma and chronic bronchitis, in which there is some evidence for the potential for increased sensory-efferent neural activity.Key words: tachykinin, sensory nerves, mucus, mucus secretion, asthma.
Multiple affinity and guanine nucleotide sensitive forms of the calcitonin gene related peptide (CGRP) receptor
Authors: Chatterjee Tapan K. , Fisher Rory A.
Published: April 2011

Calcitonin gene related peptide (CGRP) is a novel neuropeptide with an impressive array of biological actions consistent with its diverse tissue distribution and suggested role as neurotransmitter or neuromodulator. Binding sites for CGRP with properties consistent with those of receptors are present in both central and peripheral tissues. Radioligand binding studies were performed to investigate the fundamental processes underlying CGRP receptor activation and signaling following agonist occupancy of the receptor. These studies documented the existence of a selective, high affinity, and homogeneous population of binding sites for CGRP in membranes prepared from central and various peripheral tissues. The affinity of [125I]CGRP for these sites was regulated by GTP or its stable analog GTPγS, indicating coupling of CGRP receptors to G-protein(s). Kinetic studies documented the existence of the CGRP receptor in multiple affinity states when both coupled to and uncoupled from G-proteins(s). These findings suggest that CGRP occupancy of its receptor induces conformational changes in the receptor that may be involved in its coupling to G-proteins and that the resulting ligand–receptor–G-protein ternary complex exists in multiple affinity conformational states. It seems likely that the multiple affinity states of the CGRP receptor ternary complex are involved differentially in signaling by and desensitization of the receptor. This evidence for agonist-induced conformational changes in a G-protein-coupled receptor prior to its coupling with G-protein(s) and for the existence of the ligand–receptor–G-protein ternary complex in multiple affinity conformational states is novel and extends our current understanding of the nature of the processes involved in agonist-dependent activation of G-protein-coupled receptors.Key words: calcitonin gene related peptide receptor, G-protein, multiple affinity.
Receptors for calcitonin gene related peptide (CGRP) in gastrointestinal epithelia
Authors: Cox Helen M.
Published: April 2011

A pharmacological comparison of calcitonin gene related peptide (CGRP) receptors expressed in normal rat colon mucosa and two human adenocarcinoma cell lines has been undertaken. Using voltage-clamp techniques electrogenic ion transport was continuously monitored across either mucosal preparations or confluent epithelial monolayers grown on permeable supports. The data presented at this meeting show that CGRP receptors are preferentially located on the basolateral epithelial surface and that their stimulation by a variety of CGRP analogues results in enhanced Cl− secretion mediated via a cyclic AMP dependent mechanism. Responses to rat αCGRP in rat descending colon mucosa and in the adenocarcinoma cell line Colony-29 are insensitive to the inhibitory effects of the C-terminal fragment human CGRP(8–37); however, significant inhibition of rat αCGRP responses was observed in the parent epithelial cell line HCA-7. This together with the subtle differences seen in agonist orders of potency in the three preparations indicates that different CGRP receptor subtypes exist in the basolateral domains of HCA-7 compared with rat colon and Colony-29 epithelia.Key words: calcitonin gene related peptide, receptors, ion transport, rat colon, epithelial cell lines.
Vasodilator effect of human adrenomedullin(13 – 52) on hypertensive rats
Authors: Tian Q. , Zhao D. , Tan D. Y. , Zhao Y. T. , Li Q. H. , Qiu J. X. , Song L. W. , Gong C. N. , Yang J. , Tang J. , Lippton H. , Hyman A. L. , Chang J. K.
Published: April 2011

Human adrenomedullin (hADM) is a newly isolated peptide with hypotensive activity in normotensive rats. The objective of this study was to investigate the effect of hADM(13–52) on hypertensive animals. hADM(13–52) induced a dose-dependent decrease in the blood pressure of spontaneously hypertensive rats and renal hypertensive rats. This result suggests that hADM is a novel antihypertensive peptide. In isolated rat aortic arteries, hADM(13–52) produced nitric oxide dependent relaxation and inhibited endothelin 1 and angiotensin II release. These in vitro effects may represent the molecular mechanisms underlying the hypotensive action of hADM in vivo.Key words: human adrenomedullin, nitric oxide, endothelin 1, angiotensin II, hypertension.
Clinical perspectives of calcitonin gene related peptide pharmacology
Authors: Feuerstein Glora , Willette Robert , Aiyar Nambi
Published: April 2011

Calcitonin gene related peptide (CGRP), a potent vasoactive and cardiotonic peptide, interacts with specific G-protein-coupled receptors. CGRP is synthesized and released from small, capsaicin-sensitive sensory nerves. This extensive network of sensory nerves, found in virtually all organs, suggest a potential role for CGRP in diverse physiologic and pathophysiologic processes. The potent vasodilation elicited by CGRP in the cerebral, coronary, and peripheral vasculature has led to its therapeutic evaluation in the treatment of cerebral vasospasm following subarachnoid hemorrhage, stable angina, and Raynaud's phenomenon. The potential inotropic action and coronary vasodilation have also led to a potential beneficial effect in congestive heart failure. The enriched localization of CGRP in trigeminal sensory ganglia may indicate a role in the neurogenic inflammation associated with migraine. Thus, CGRP antagonists may represent a novel therapeutic approach to the treatment of migraine. In addition, CGRP and amylin (homologous pancreatic peptide) reduce the tissue–glucose response to insulin. It has been suggested that a CGRP antagonist may therefore improve insulin sensitivity in non-insulin-dependent diabetes, NIDDM. This brief review provides a preliminary exploration of the potential therapeutic opportunities surrounding CGRP and CGRP antagonists. Future advances are dependent on a better understanding of the structure and function of CGRP receptor(s) and the concomitant identification of selective and potent agonists and antagonists useful for addressing therapeutic hypotheses.Key words: calcitonin gene related peptide, congestive heart failure, diabetes, therapy, vasospasm, migraine.
Comparative affinities of human adrenomedullin for 125I-labelled human alpha calcitonin gene related peptide ([125I)hCGRPα) and 125I-labelled Bolton – Hunter rat amylin ([125I]BHrAMY) specific binding sites in the rat brain
Authors: Rossum D. van , Ménard D. P. , Quirion R. , Chang J. K.
Published: April 2011

Adrenomedullin (ADM) is a recently identified peptide that shows some homology (~ 25%) with calcitonin gene related peptide (CGRP) and is now considered to be a new member of this peptide family. Because it shares biological effects with CGRP, we evaluated the possible affinity of human adrenomedullin (hADM) for 125I-labelled human CGRPα ([125I]hCGRPα) binding sites in the rat brain. Moreover, we evaluated the potential existence of cross-reactivity for 125I-labelled Bolton–Hunter rat amylin ([125I]BHrAMY), another member of this peptide family. In all brain areas investigated, hADM only competed with relatively low affinities for both [125I]hCGRPα and [125I]BHrAMY binding sites, with IC50 values generally in the high nanomolar – low micromolar range, the lowest affinity being observed for [125I]BHrAMY binding sites. Interestingly, the lowest affinities of hADM against both radioligands were detected in the nucleus accumbens and ventral striatum. These areas are known to be enriched with atypical CGRP – salmon calcitonin – amylin sensitive sites. It thus appears that hADM is unlikely to bind to this atypical site. Moreover, hADM demonstrated limited affinity for either [125I]hCGRPα or [125I]BHrAMY binding sites in the rat brain. This suggests that the potential biological effects of ADM in the brain could be mediated through a different class of receptors with higher affinity for this newly isolated peptide.Key words: adrenomedullin, calcitonin gene related peptide, amylin, rat brain.
The 1994 Upjohn Award Lecture. Molecular and genetic approaches to the study of signal transduction in the adrenal cortex
Authors: Schimmer Bernard P.
Published: April 2011

This review highlights contributions from my laboratory in which the sites and mechanisms of action of the adrenocorticotropic hormone (ACTH) in the adrenal cortex have been explored. Early studies showing that ACTH stimulates adrenal steroidogenesis by interacting with specific receptors at the cell surface are summarized. Next, the development of a strategy of genetic analysis to define the signalling events that follow ACTH interaction with its receptor is described. This strategy involved the isolation and characterization of mutant adrenal cell lines harboring specific defects in the ACTH-responsive steroidogenic pathway. I describe the isolation and characterization of several of these mutants and demonstrate how these mutants have helped to establish obligatory roles for adenylyl cyclase, cyclic AMP (cAMP), and cAMP-dependent protein kinase in the steroidogenic actions of ACTH. Finally, some of our studies on the regulated expression of the steroidogenic cytochrome P450 enzymes in Y1 adrenal cells are reviewed. These latter studies have led to the discovery of a novel promoter element and transcription factor (designated steroidogenic factor 1) that participates in the coordinate expression of these cytochrome P450 enzymes and that is required for their regulated expression by ACTH and cAMP.Key words: adrenocorticotropic hormone, cyclic AMP, cytochrome P450 genes, steroidogenesis, Y1 adrenocortical tumor cells.
Effects of prolonged low frequency stimulation on skeletal muscle sarcoplasmic reticulum
Authors: Chin E. R. , Green H. J , Grange F. , Dossett-Mercer J. , O'Brien P. J.
Published: April 2011

The role of prolonged electrical stimulation on sarcoplasmic reticulum (SR) Ca2+sequestration measured in vitro and muscle energy status in fast white and red skeletal muscle was investigated. Fatigue was induced by 90 min intermittent 10-Hz stimulation of rat gastrocnemius muscle, which led to reductions (p < 0.05) in ATP, creatine phosphate, and glycogen of 16, 55, and 49%, respectively, compared with non-stimulated muscle. Stimulation also resulted in increases (p < 0.05) in muscle lactate, creatine, Pi, total ADP, total AMP, IMP, and inosine. Calculated free ADP (ADPf) and free AMP (AMPf) were elevated 3- and 15-fold, respectively. No differences were found in the metabolic response between tissues obtained from the white (WG) and red (RG) regions of the gastrocnemius. No significant reductions in SR Ca2+ATPase activity were observed in homogenate (HOM) or a crude SR fraction (CM) from WG or RG muscle following exercise. Maximum Ca2+uptake in HOM and CM preparations was similar in control (C) and stimulated (St) muscles. However, Ca2+uptake at 400 nM free Ca2+was significantly reduced in CM from RG (0.108 ± 0.04 to 0.076 ± 0.02 μmol∙mg−1protein∙min−1in RG–C and RG–St, respectively). Collectively, these data suggest that reductions in muscle energy status are dissociated from changes in SR Ca2+ATPase activity in vitro but are related to Ca2+uptake at physiological free [Ca2+] in fractionated SR from highly oxidative muscle. Dissociation of SR Ca2+ATPase activity from Ca2+uptake may reflect differences in the mechanisms evaluated by these techniques.Key words: sarcoplasmic reticulum, contractile activity, Ca2+sequestration, energy status, red and white gastrocnemius.
Calsequestrin is essential for the Ca2+release induced by myotoxin α in skeletal muscle sarcoplasmic reticulum
Authors: Ohkura Masamichi , Furukawa Ken-Ichi , Ohizumi Yasushi , Ide Tory , Kawasaki Takashi , Kasai Michiki
Published: April 2011

Myotoxin α (MYTX), a polypeptide toxin purified from the venom of prairie rattlesnakes (Crotalus viridis viridis), induced Ca2+release from the heavy fraction of skeletal sarcoplasmic reticulum (HSR), using a Ca2+electrode. The effect of MYTX was nearly abolished by pretreatment with ryanodine, an alkaloid-based Ca2+channel blocker. In the stopped-flow experiments, MYTX increased the choline+permeability of HSR in the presence of calsequestrin (CS). Single channel recording experiments showed that in the presence of CS, the channel currents were markedly enhanced by MYTX applied to the cis side, but not to the trans side. However, in the absence of CS, MYTX failed to cause the excitatory effect in both the experiments. These results suggest that CS is essential for MYTX-induced Ca2+release through the Ca2+release channels in skeletal HSR.Key words: calsequestrin, myotoxin α, Ca2+release, Ca2+release channels, sarcoplasmic reticulum.
Detection of functional receptors for the proteinase-activated-receptor-2-activating polypeptide, SLIGRL-NH2, in rat vascular and gastric smooth muscle
Authors: Al-Ani Bahjaf , Saifeddine Mahmoud , Hollenberg Morley D.
Published: April 2011

We have studied the actions of the proteinase-activated-receptor-2 (PAR2)-activating polypeptide, SLIGRL-NH2(SLI-NH2), in rat aorta and in gastric longitudinal muscle preparations. In the phenylephrine-precontracted aorta preparation, SLI-NH2caused an endothelium-dependent relaxation that mimicked the action of low concentrations (0.5 U/mL) of trypsin and that was blocked by the nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester. In endothelium-free aorta ring preparations, SLI-NH2caused neither a relaxation nor a contraction. In the gastric longitudinal muscle preparation, SLI-NH2caused a transient contraction that mimicked the action of trypsin (0.5 U/mL) and that was sensitive to inhibitors of cyclooxygenase (indomethacin) and tyrosine kinase (genistein). Further, using a reverse-transcriptase – polymerase chain reaction (RT–PCR) approach we detected, in both assay tissues, mRNA for the rat PAR2receptor, and we ascertained, using a cloned receptor cDNA obtained from a rat intestinal cDNA library, that the putative N-terminal activating peptide sequence of the rat PAR2receptor (SLIGRL) is identical with the one previously cloned from murine tissue. We concluded that, like the thrombin receptor, the PAR2receptor may play a pathophysiologic role in the regulation of vascular and gastric smooth muscle contractility.Key words: thrombin, proteinase-activated receptor 2, protease, smooth muscle.
Characterization of nucleoside transport activity in rabbit cortical synaptosomes
Authors: James Kenneth W. , Hammond James R.
Published: April 2011

Rabbit central nervous system (CNS) preparations have been used to study the central effects of adenosine, but little is known about the specific uptake mechanisms in rabbit brain involved in the regulation of extracellular adenosine concentrations. The present study assessed the kinetic and pharmacological characteristics of the uptake of [3H]uridine (a poorly metabolized substrate for adenosine transporters) by rabbit cortical synaptosomes, to define the transporter subtypes involved and to evaluate species variability in transporter characteristics. [3H]Uridine transport into rabbit cortical synaptosomes was mediated by two saturable, facilitated diffusion systems with characteristics compatible with the es and ei transporter subtypes identified in other mammalian species. About 65% of the total transport was mediated by the es system, and Kmestimates of 320 and 94 μM were determined for [3H]uridine uptake by the es and ei transporter, respectively. These results differ significantly from the subtype ratio and kinetic characteristics reported for rat and guinea pig cortical synaptosomes, where most of the transport was mediated by an ei subtype. Dipyridamole, dilazep, nitrobenzylthioinosine, R75231, solufiazine, and mioflazine were relatively more effective as inhibitors of es-mediated uptake (compared with ei), while the substrates adenosine, cytidine, and guanosine did not distinguish between the es and ei transporters in rabbit cortical synaptosomes. These results highlight the significant species–tissue variability in nucleoside transporter characteristics and subtype expression, and emphasize the need to characterize the transporters in human CNS tissue to allow the rational development of CNS-active therapeutics based on inhibition of nucleoside transport.Key words: nitrobenzylthioinosine, [3H]uridine, nucleoside transport, central nervous system, adenosine.
Calcium regulation of glycolysis, glucose oxidation and fatty acid oxidation in the aerobic and ischemic heart
Authors: Schönekess Brett , Brindley Peter G. , Lopaschuk Gary O.
Published: April 2011

Although Ca2+is an important regulator of energy metabolism, the effects of increasing extracellular [Ca2+] on energy substrate preference are not clear. We determined the relationship between [Ca2+], fatty acids, and ischemia on rates of glycolysis, glucose oxidation, and palmitate oxidation in isolated working rat hearts. Hearts were perfused with Krebs–Henseleit buffer containing 11 mM glucose, 100 μU/mL insulin, and either 1.25 or 2.5 mM Ca2+, in the presence or absence of 1.2 mM palmitate. Rates of glycolysis and glucose oxidation or palmitate oxidation were measured in the hearts using [5-3H,14C(U)]glucose or [1-14C]palmitate, respectively. In the absence of fatty acids, glycolysis and glucose oxidation rates were similar, regardless of whether [Ca2+] was 1.25 or 2.5 mM. Addition of 1.2 mM palmitate to the perfusate of hearts perfused with 1.25 mM Ca2+significantly decreased rates of both glycolysis (from 4623 ± 438 to 1378 ± 238 nmol∙min−1∙g−1dry weight) and glucose oxidation (from 1392 ± 219 to 114 ± 22 nmol∙min−1∙g−1dry weight). When [Ca2+] was increased from 1.25 to 2.5 mM in hearts perfused with 1.2 mM palmitate, glycolysis and glucose oxidation increased by 164 and 271%, respectively, with no change in palmitate oxidation rates. Increasing [Ca2+] from 1.25 to 2.5 mM increased the contribution of glucose to ATP production from 9.3 to 18.7%. When hearts were subjected to low-flow ischemia (by reducing coronary flow to 0.5 mL∙min−1) oxidative metabolism was essentially abolished. Under these conditions, glycolytic rates were not dependent on either [Ca2+] or the presence or absence of fatty acids. These results demonstrate that perfusate [Ca2+] is an important determinant of myocardial glucose metabolism in aerobic hearts, and that glycolysis and glucose oxidation are more responsive to changes in [Ca2+] than is fatty acid oxidation.Key words: β-oxidation, glucose oxidation, pyruvate dehydrogenase complex.
Vascular capacitance and cardiac output in pacing-induced canine models of acute and chronic heart failure
Authors: Ogilvie Richard Ian , Zborowska-Sluis Danuta
Published: April 2011

The relationship between stressed and total blood volume, total vascular capacitance, central blood volume, cardiac output (CO), and pulmonary capillary wedge pressure (Ppcw) was investigated in pacing-induced acute and chronic heart failure. Acute heart failure was induced in anesthetized splenectomized dogs by a volume load (20 mL/kg over 10 min) during rapid right ventricular pacing at 250 beats/min (RRVP) for 60 min. Chronic heart failure was induced by continuous RRVP for 2–6 weeks (average 24 ± 2 days). Total vascular compliance and capacitance were calculated from the mean circulatory filling pressure (Pmcf) during transient circulatory arrest after acetylcholine at three different circulating volumes. Stressed blood volume was calculated as a product of compliance and Pmcf, with the total blood volume measured by a dye dilution. Central blood volume (CBV) and CO were measured by thermodilution. Central (heart and lung) vascular capacitance was estimated from the plot of Ppcw against CBV. Acute volume loading without RRVP increased capacitance and CO, whereas after volume loading with RRVP, capacitance and CO were unaltered from baseline. Chronic RRVP reduced capacitance and CO. All interventions, volume ± RRVP or chronic RRVP, increased stressed and central blood volumes and Ppcw. Acute or chronic RRVP reduced central vascular capacitance. Cardiac output was increased when stressed and unstressed blood volumes increased proportionately as during volume loading alone. When CO was reduced and Ppcw increased, as during chronic RRVP or acute RRVP plus a volume load, stressed blood volume was increased and unstressed blood volume was decreased. Thus, interventions that reduced CO and increased Ppcw also increased stressed and reduced unstressed blood volume and total vascular capacitance.Key words: vascular capacitance, vascular compliance, central blood volume, rapid ventricular pacing, dogs, heart failure.
Prevention of stroke and preservation of the functions of cerebral arteries by treatment with perindopril in stroke-prone spontaneously hypertensive rats
Authors: Wang H , Smeda J S , Lee RMKW
Published: April 2011

The aim of this study was to determine whether the prevention of stroke with perindopril treatment in stroke-prone spontaneously hypertensive rats (SHRSP) is associated with the preservation of the myogenic properties of the cerebral arteries. After weaning at 4 weeks of age, male SHRSP were fed a Japanese-style rat diet with high salt to induce stroke development. Treatment with perindopril was given by gavage every morning beginning at 6 weeks of age. There were three experimental groups: two groups treated with 4 mg ·kg-1 ·day-1 perindopril for different durations (8 or 12 weeks) and one control group consisting of littermates given distilled water. All the control animals developed stroke and died within 14 weeks of age, and myogenic response of the middle cerebral arteries (MCA) to pressure increase was lost in these animals. In contrast, all the treated SHRSP survived during the treatment period, and myogenic response of the MCA was preserved. After withdrawal of the treatment, SHRSP treated for a longer period (12 weeks) also survived longer than those treated for a shorter period (8 weeks). The subsequent development of stroke and death following treatment withdrawal after 8 or 12 weeks of treatment was associated with the loss of pressure-dependent constriction in MCA. A longer treatment duration also increased the stiffness of the MCA. MCA from SHRSP after 12 weeks of treatment had smaller external and lumen diameters, and thicker walls than those from the 8-week treatment group. In a separate study, we found that treatment of SHRSP with 1 or 4 mg ·kg-1 ·day-1 of perindopril for 24 weeks beginning at 6 weeks of age also protected them against death related to stroke, because these rats survived up to 43 weeks of age, when the experiment was terminated. We conclude that there is an association between the absence of myogenic response in cerebral arteries and stroke development in SHRSP. Perindopril treatment preserves the myogenic response of MCA in SHRSP and prevents the stroke development in these animals. A prolonged treatment could increase the survival of SHRSP through a remodelling of the MCA and increasing the stiffness of the cerebral arteries.Key words: autoregulation, myogenic response, cerebral artery, stroke, perindopril, hypertension.
Resurgence of carbon monoxide: an endogenous gaseous vasorelaxing factor
Authors: Wang Rui
Published: April 2011

Carbon monoxide (CO) is an endogenously generated gas that may play an important physiological role in the regulation of vascular tone. The CO-induced vasorelaxation, as a result of a direct action on vascular smooth muscles, has been demonstrated in many cases. Three major cellular mechanisms are proposed to explain the vasorelaxing effect of CO. These include the activation of soluble guanylyl cyclase, stimulation of various types of K channels, and inhibition of the cytochrome P450 dependent monooxygenase system in vascular smooth muscle cells. An interaction between CO and nitric oxide may also significantly contribute to the fine tuning of vascular tone. Furthermore, alterations in either the endogenous production of CO or the vascular responsiveness to CO have been encountered in several pathophysiological situations. A better understanding of the vascular effects of CO and the underlying cellular and molecular mechanisms will pave the way for the establishment of the role played by CO in vascular physiology and pathophysiology.Key words: carbon monoxide, heme oxygenase, smooth muscles, vasorelaxation.
Acute effects of prolactin on passive calcium absorption in the small intestine by in vivo perfusion technique
Authors: Krishnamra Nateetip , Wirunrattanakij Yinglak , Limlomwongse Liangchai
Published: April 2011

The acute effect of intraperitoneally administered prolactin (0.2, 0.4, and 0.6 mg/kg body weight) on passive calcium transport in duodenum, proximal jejunum, and ileum of sexually mature female Wistar rats was investigated by using an in vivo perfusion technique. Test solution containing (in mM) NaCl, 100; KCl, 4.7; MgSO4, 1.2; CaCl2, 20; D-glucose, 11; sodium ferrocyanide (Na4Fe(CN)6), an index of net water transport, 20; and 0.7 µCi45CaCl2(1 Ci = 37 GBq) was perfused through the 10-cm intestinal loop for 60 min. Results showed that 0.4 mg prolactin/kg body weight significantly increased duodenal net Ca absorption (net Ca) from 23.81 ± 1.84 to 30.56 ± 1.57 mmol/g dry weight (p < 0.05) by stimulating the lumen to plasma calcium flux (CaL-P). The jejunum responded to 0.2, 0.4, and 0.6 mg prolactin/kg body weight by reversing from net Ca absorption of 18.60 ± 1.70 mmol/g dry weight to net secretion of -3.30 ± 1.56, -10.39 ± 2.21, and -11.79 ± 2.04 mmol/g dry weight (p < 0.01), respectively, as a result of a dose-dependent increase in plasma to lumen calcium flux (CaP-L). Calcium fluxes in the ileum on the other hand did not respond to prolactin. There was a close correlation between net water flux and net calcium flux in all three intestinal segments under basal condition regardless of the luminal sodium concentration. However, this correlation was lost after prolactin administration, which while having no effect on net water flux, altered the duodenal and jejunal calcium fluxes. By varying the luminal concentration of sodium, it was found that the stimulatory effect of 0.4 mg prolactin/kg body weight on the duodenal CaL-Pwas reduced when compared with control, i.e., 17.84 ± 0.91 vs. 26.64 ± 1.05 mmol/g dry weight at a sodium concentration of 180 mM, and 14.48 ± 0.99 vs. 20.12 ± 1.34 mmol/g dry weight at a sodium concentration of 140 mM. At a sodium concentration of 80 mM, the prolactin effect was absent. Since duodenal Na+-K+ATPase activity was increased by prolactin from 3.77 ± 0.16 to 4.95 ± 0.30 µmol Pi·mg-1protein ·h-1(p < 0.05), sodium dependency of the prolactin-enhanced lumen to plasma calcium flux may be related to both sodium-induced water flow and calcium-sodium exchange across the basolateral membrane. Thus, it was postulated that under basal condition, net calcium transport in the small intestine occurred with the sodium-induced water transport along the paracellular pathway. However, after prolactin administration, this association was lost. Prolactin-enhanced lumen to plasma calcium flux in the duodenum was sodium dependent and involved the Na+-K+ATPase activity. In the proximal jejunum, prolactin stimulated plasma to lumen calcium flux, but the mechanism was not known.Key words: calcium absorption, calcium fluxes, Na-K ATPase, perfusion technique, prolactin.
Serum leptin levels and energy expenditure in normal weight women
Authors: Martin L J , Jones PJH , Considine R V , Su W , Boyd N F , Caro J F
Published: April 2011

To investigate whether circulating leptin levels are associated with energy expenditure in healthy humans, doubly labeled water energy measurements and food intake assessment were carried out in 27 women (mean age, 48.6 years; weight, 61.9 kg; body mass index, 23.2). Energy expenditure was determined over 13 days. Food intake was measured by 7-day food records. Leptin was measured by radioimmunoassay. Leptin level was strongly associated with percentage body fat (r = 0.59; p < 0.001), fat mass (r = 0.60; p < 0.001), and body mass index (r = 0.41; p = 0.03), but no correlation was observed with energy expenditure (r = 0.02; p = 0.93). After controlling for percentage body fat, a positive association of leptin level with energy expenditure of marginal significance (p = 0.06) was observed. There were no significant univariate associations of age, physical activity, lean body mass, height, or dietary variables with leptin level. When controlling for body fat, a significant positive correlation was observed for percent energy from carbohydrate and negative correlations with dietary fat and alcohol intake. These findings confirm previous associations between leptin and body fat content and suggest a relationship between serum leptin and energy expenditure level in healthy humans.Key words: leptin, energy expenditure, body composition, diet.
Gentamicin uptake by LLCPK1cells: effect of intracellular and extracellular pH changes
Authors: Lui Eric Chi-Chung , Bendayan Reina
Published: April 2011

The mechanisms by which aminoglycosides are transported across the luminal membrane of renal proximal tubular cells remain unclear. A luminal organic cation/H+exchange as well as an adsorptive endocytosis membrane process has been proposed to be involved in gentamicin renal accumulation. The objectives of this work were to explore further the effects of intracellular and extracellular pH changes on gentamicin uptake. [3H]Gentamicin uptake by a continuous renal epithelial cell line, LLCPK1, grown as a monolayer on an impermeable surface was measured at different temperatures and pH conditions and in the presence of various inhibitors. Uptake of gentamicin was found to be carrier mediated (Km= 1.26 ± 0.22 mM, Vmax= 289 ± 27 pmol ·mg-1·min-1), energy dependent (inhibited in part by sodium azide), and temperature dependent (37°C > 4°C). Fifteen-minute gentamicin (10 µM) uptake was inhibited by 1 mM of the organic cations cimetidine (61.0%), quinidine (73.5%), quinine (68.6%), and verapamil (61.5%). More importantly, while an outwardly directed proton gradient did not have a significant effect on gentamicin uptake, extracellular acidification (pH 6.5), which leads to a higher degree of gentamicin ionization, significantly enhanced gentamicin uptake by LLCPK1monolayer cells. These results suggest that the luminal organic cation/H+exchanger is not involved in gentamicin uptake by renal cultured epithelial cells. Rather, the cationic charge of gentamicin appears to be one of the primary determinants for renal luminal uptake.Key words: gentamicin, LLCPK1cells, pH, nephrotoxicity.
Comparison of the contractile performance of the hypertrophied myocardium from spontaneous hypertensive rats and normotensive infarcted rats
Authors: Mill J G , Novaes MAS , Galon M , Nogueira J B , Vassallo D V
Published: April 2011

The sarcoplasmic reticulum (SR) exerts a key role on the excitation-contraction coupling process in the myocardium. Since the relation between the volume of cellular organelles, such as SR, and the sarcolemmal area of myocytes is not uniform in myocardial hypertrophy of different etiologies, we compared the contractile performances of hypertrophied left ventricular papillary muscles from rats with pressure overload and with volume overload. Hemodynamically compensated spontaneous hypertensive rats (SHR, 3 months old, systolic blood pressure = 189 ± 4 mmHg, n = 8) and Wistar rats with healed (30 days) myocardial infarction (MI, n = 7) produced by ligation of the left coronary artery were used. Results were compared with age-matched Wistar control (CON) rats (n = 13). Force (F), corrected to muscle cross-sectional area (g/mm2), and dF/dt were recorded in muscles contracting isometrically and stretched to Lmax. The inotropic response to increasing extracellular Ca2+ concentrations (1.25 to 5.0 mM) was compared in twitches (0.5 Hz) and during tetanic stimulation (5 Hz, 30 s) in the muscles treated with 1 µM ryanodine. F recorded in basal conditions (Ca = 1.25 mM, 0.5 Hz) in the CON group (1.34 ± 0.20 g/mm2) was higher (p < 0.05) than in the MI (0.73 ± 0.13 g/mm2) and lower (p < 0.05) than in the SHR group (2.08 ± 0.25 g/mm2). Similar differences between groups were also observed in relation to +dF/dt. Increasing extracellular Ca produced a parallel increase of F and +dF/dt in the three groups of muscles. Ryanodine treatment reduced F and +dF/dt in all groups and completely inhibited the development of force in post-rest contractions, indicating SR inhibition. SHR muscles were more sensitive to ryanodine than CON and MI (F decrease = 64 ± 7, 51 ± 5, and 22 ± 5%, respectively, p < 0.05). The tetanic tension (Ca = 1.25 mM) was similar in SHR and CON (0.82 ± 0.19 and 0.92 ± 0.18 g/mm2; p > 0.05) and depressed in the MI group (0.35 ± 0.12 g/mm2). These data suggest an increased participation of SR as source of activator Ca in the hypertrophied muscle of SHR. This adaptation likely contributes to maintain the normal cardiac function in hemodynamically compensated SHR, despite increasing afterload levels. This adaptation seems not to occur after MI, which may contribute to the depressed contractile performance of the left ventricular muscle surviving to infarction.Key words: myocardial contractility, myocardial hypertrophy, sarcoplasmic reticulum, myocardial infarction, hypertension.
Dynorphin A(1-8): stability and implications for in vitro opioid activity
Authors: Bell K M , Traynor J R
Published: April 2011

The opioid binding profile and in vitro activity of the endogenous opioid peptide dynorphin A(1-8) have been studied. At opioid receptors in guinea-pig brain dynorphin A(1-8) was nonselective, although with some preference for the delta receptor (Ki 4.6 nM) over µ (Ki 18 nM) and kappa (Ki 40 nM) receptors. However, a high degree of metabolism was observed, with less than 10% of added dynorphin A(1-8) remaining at the end of the binding assay. In the presence of peptidase inhibitors to prevent breakdown of the N- and C-termini and the Gly3-Phe4 bond the major metabolite was [Leu5]enkephalin (representing 49% recovered material). This was reduced by inclusion of an inhibitor of endopeptidase EC 3.4.24.15. In the presence of all the peptidase inhibitors the affinity for kappa receptors (Ki 0.5 nM) relative to µ and delta receptors increased, but no selectivity of binding was observed. This lack of selectivity was confirmed using membranes from C6 glioma cells expressing rat opioid receptors. The agonist effect of dynorphin A(1-8) in the mouse vas deferens (EC50 116 nM) and guinea-pig ileum (EC50 38 nM) was mediated through the kappa receptor as evidenced by the rightward shifts afforded by the kappa -selective antagonist norbinaltorphimine. In the presence of peptidase inhibition potency was improved 2-fold in the mouse vas deferens and 20-fold in the guinea-pig ileum, but this agonist activity was mediated through delta receptors in the vas deferens and µ receptors in the ileum, as a result of the formation and stabilization of [Leu5]enkephalin. The results confirm the absence of receptor selectivity of dynorphin A(1-8) in binding assays but show that its agonist effects, at least in vitro, are mediated exclusively through the kappa opioid receptor.Key words: dynorphin A(1-8), opioid receptors, peptide metabolism, mouse vas deferens, guinea-pig ileum.
Transient upregulation of μ opioid receptor mRNA levels in nucleus accumbens during chronic cocaine administration
Authors: Azaryan Anahit V , Clock Barbara J , Rosenberger John G , Cox Brian M
Published: April 2011

Chronic continuous cocaine administration for 3 days has been shown to upregulate the level of µ opioid receptor (MOR) mRNA in the nucleus accumbens (n. acc.) of rat brain. Dopamine (DA) antagonists, SCH 23390, eticlopride, and nafadotride, blocked, and DA agonists, SKF 38393, R(+)-6-bromo-APB hydrobromide, and bromocriptine, mimicked the cocaine-induced upregulation of MOR mRNA, suggesting involvement of both subfamilies of DA receptors in the effect of cocaine. In the present study the time course of cocaine-induced and DA agonist induced alterations in the level of MOR mRNA in n. acc. has been determined and compared with the changes in the level of MOR binding sites. Male Sprague-Dawley rats were treated with saline, cocaine (50 mg ·kg-1·day-1), or DA agonists for periods between 24 and 336 h. Expression of MOR mRNA in n. acc. was estimated using quantitative competitive polymerase chain reaction assays following reverse transcription. The cocaine-induced upregulation of MOR mRNA in n. acc. was transient, developing 2 days after exposure, and peaking at 3 days with return to baseline levels by 4 days of chronic continuous cocaine treatment. The temporal characteristics of DA agonist induced increase in the levels of MOR mRNA in n. acc. were similar to those of cocaine, with maximum effect after 3 days of treatment. The density of [3H]DAMGO binding sites in n. acc. was 30% higher after 3 days of cocaine administration than in saline-treated control animals, but returned toward baseline levels after 4 days of cocaine treatment. No changes in the binding of [3H]DAMGO were detected after 7 or 14 days exposure to cocaine. The affinity of [3H]DAMGO to n. acc. membranes (~2.0 nM) was unchanged during the cocaine treatment.Key words: cocaine, dopamine, dopamine agonists, µ opioid receptor, nucleus accumbens, polymerase chain reaction.
Effects of a selective phosphodiesterase IV inhibitor (CDP-840) in a leukotriene-dependent non-human primate model of allergic asthma
Authors: Jones T R , McAuliffe M , McFarlane C S , Piechuta H , Macdonald D , Rodger I W
Published: April 2011

The activity of CDP-840, a novel, selective phosphodiesterase IV inhibitor was determined in a leukotriene-dependent non-human primate model of allergic asthma. Measurements of specific airway resistance (sRaw) were recorded in a dual chamber plethysmograph for 1 h and 3-5 h after challenge of allergic conscious squirrel monkeys with an aerosol of ascaris antigen. Orally administered CDP-840 (10 mg/kg; 1 h before challenge) produced partial inhibition (41 and 45%, respectively) of both the acute (1 h post antigen) response and the late (3-5 h post antigen) response to antigen but failed to alter the response to an aerosol of leukotriene D4. In a second series of experiments, intravenous CDP-840 (5 mg/kg; 30 min before challenge) showed improved potency, producing 82% inhibition of the early and 51% inhibition of the late phase response. CDP-840 was inactive when tested intravenously at 1 mg/kg and was inactive against the 3-5 h response when administered after the early phase response (5 mg/kg; i.v. 60 min post antigen challenge). The novel phosphodiesterase IV inhibitor CDP-840 selectively inhibited antigen-induced bronchoconstriction in conscious squirrel monkeys. This effect appears to be independent of any direct bronchodilator action. It is concluded that the activity of CDP-840 in this model may be due to an inhibitory effect on mediator (e.g., leukotriene) release.Key words: selective phosphodiesterase IV inhibitor, CDP-840, antigen-induced bronchoconstriction, non-human primate.
Cutaneous Merkel cells of the rat contain both dynorphin A and vesicular monoamine transporter type 1 (VMAT1) immunoreactivity
Authors: Weihe Eberhard , Hartschuh Wolfgang , Schäfer Martin KH , Romeo Horacio , Eiden Lee E
Published: April 2011

To delineate fully opioid peptide function in cutaneous inflammatory and nociceptive responses, it is necessary to know first which opioid peptides are present in the skin and which cellular elements in the skin store and secrete them. Merkel cells are cutaneous neuroendocrine cells, which may derive from the neural crest or from undifferentiated keratinocytes with stem cell character. The neuroendocrine character of Merkel cells is supported by their immunoreactivity for chromogranin A (CGA) and a variety of neuropeptides, among them the opioid peptide [Met]enkephalin as shown in guinea-pig and mouse. This study investigates in the rat whether the preprodynorphin derived opioid peptide dynorphin A is expressed in cutaneous Merkel cells and possibly related to an aminergic phenotype. Light microscopic immunohistochemistry revealed dynorphin A immunoreactivity in Merkel cells to be codistributed with immunoreactivity for calcitonin gene-related peptide (CGRP) and CGA, two well-established marker peptides of mammalian Merkel cells. Vibrissal Merkel cells stained for the neuroendocrine vesicular monoamine transporter isoform 1 (VMAT1) but not for the predominantly neuronal isoform 2 (VMAT2). Merkel cell staining for dynorphin A, VMAT1, CGA, and CGRP was unaffected by experimental denervation. Dynorphin A and a still unidentified monoamine, possibly serotonin, may cofunction as autocrine or paracrine mediators in the mechanosensory Merkel cell - axon complex and are potentially involved in peripheral analgesia.Key words: skin, opioid, neuropeptide, neuroendocrine, pain.