bluuebunny/crossref_metadata_2025 huggingface dataset:
An assessment of phosphodiesterase activity in situ after treatment of hepatocytes with hormones
Authors: Gettys T. W. , Blackmore P. F. , Corbin J. D.
Published: December 2017

The role of phosphodiesterase activation in controlling adenosine 3',5'-cyclic monophosphate (cAMP) levels within hepatocytes was investigated by preloading hepatocytes with the hydrolyzable cAMP analogue 8-para-chlorophenylthio-cAMP (8-pCl phi S-cAMP) and measuring disappearance of the analogue after treating the cells with various hormones. Incubation of hepatocytes with 15 nM 8-pCl phi S-cAMP increased the intracellular concentration of the analogue at 0.5 and 2 min, but by 5 min the concentration plateaued and remained constant or declined slightly at 7 and 10 min. Treatment of hepatocytes with 5 nM glucagon led to a rapid 50% decline in intracellular concentration of the analogue. However, 6 nM insulin produced no detectable change in analogue concentration, and a combination of 5 nM glucagon and 6 nM insulin produced no greater lowering of 8-pCl phi S-cAMP than did glucagon alone. Treatment of hepatocytes with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (50 microM) blocked approximately 30% of the glucagon-mediated decrease in 8-pCl phi S-cAMP concentration, and in separate cell incubations, it blocked 50% of the cAMP lowering produced by 125 nM 8-pCl phi S-cAMP. Treatment of analogue-preloaded hepatocytes with effective concentrations of phenylephrine, vasopressin, or angiotensin resulted in no change in intracellular analogue or cAMP concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Arginine metabolism in wounds
Authors: Albina J. E. , Mills C. D. , Barbul A. , Thirkill C. E. , Henry W. L. , Mastrofrancesco B. , Caldwell M. D.
Published: December 2017

Arginine metabolism in wounds was investigated in the rat in 1) lambda-carrageenan-wounded skeletal muscle, 2) Schilling chambers, and 3) subcutaneous polyvinyl alcohol sponges. All showed decreased arginine and elevated ornithine contents and high arginase activity. Arginase could be brought to the wound by macrophages, which were found to contain arginase activity. However, arginase was expressed by macrophages only after cell lysis and no arginase was released by viable macrophages in vitro. Thus the extracellular arginase of wounds may derive from dead macrophages within the injured tissue. Wound and peritoneal macrophages exhibited arginase deiminase activity as demonstrated by the conversion of [guanido-14C]arginine to radiolabeled citrulline during culture, the inhibition of this reaction by formamidinium acetate, and the lack of prokaryotic contamination of the cultures. These findings and the known metabolic fates of the products of arginase and arginine deiminase in the cellular populations of the wound suggest the possibility of cooperativity among cells for the production of substrates for collagen synthesis.
Effect of norepinephrine on consumption of oxygen in perfused skeletal muscle from cold-exposed rats
Authors: Shiota M. , Masumi S.
Published: December 2017

The effect of norepinephrine on the consumption of O2 was studied in the skeletal muscle in the perfused hindlimbs of rats that had been kept at 4 degrees C for 5-25 days. 1) Basal rates of consumption of O2 and release of lactate were not affected by exposure to cold. 2) The stimulation of consumption of O2 by norepinephrine increased in the perfused hindlimbs of rats exposed to cold for 10-25 days, with a maximum stimulation at 20 days. The response to norepinephrine decreased markedly in hindlimbs perfused with propranolol or phentolamine. Phenylephrine, in the presence of 0.5 nM isoproterenol, stimulated the consumption of O2 at concentrations as low as 0.5 microM, with a maximum at 5 microM, in hindlimbs from the group exposed to cold for 20 days. 3) Ouabain inhibited the stimulation of consumption of O2 by norepinephrine. Norepinephrine caused a net release of K+ in control muscle but a net uptake of K+ by muscle from the group exposed to cold for 20 days. The results suggest that the calorigenic responsiveness to norepinephrine increases in skeletal muscle during acclimation of the rat to the cold, both alpha- and beta-adrenergic actions are involved in the calorigenic effects of norepinephrine, and the increased activity of the Na+-K+ ATPase under the influence of norepinephrine may be involved in the calorigenic action of norepinephrine on the skeletal muscle of cold-acclimated rats.
Influence of mechanical stretch on growth and protein turnover of rat uterus
Authors: Douglas A. J. , Clarke E. W. , Goldspink D. F.
Published: December 2017

A new technique has been developed and used to distend the uterus of nonpregnant rats for up to 5 days. Continuous distension of the saline-filled uterus induced rapid and extensive growth of the whole uterus and the myometrium by a combination of hyperplasia and hypertrophy. In both cases, 1 day after this imposition of mechanical stretch significant increases (25-50%) in the protein, RNA, and DNA contents were found, with larger changes (100-250%) being progressively expressed up to 5 days. This stretch-induced growth primarily results from a stimulation of protein synthesis (measured both in vivo and in vitro), with little or no change being evident in the rate of protein breakdown. These findings have been discussed in relation to the role of stretch in the growth of the uterus during pregnancy and stretch-induced responses found in other types of muscle.
Insulin binding, internalization, and degradation by a cultured kidney cell line
Authors: Yagil C. , Ehmann U. K. , Frank B. H. , Rabkin R.
Published: December 2017

Proximal tubules are a key site of insulin metabolism, which is in part a receptor-mediated process. To explore the interaction between insulin and the kidney and to evaluate the role of receptors in insulin uptake and processing, a study was carried out with a cultured proximal-like opossum kidney (OK) cell line. 125I-insulin associated with confluent monolayers in a specific manner, and this interaction was competitively inhibited by insulin; unrelated peptides were relatively ineffective. Insulin degradation exhibited time and temperature dependency and up to a concentration of 5 X 10(-8) M was not saturable. Degradation exhibited partial hormone specificity. Separation of plasma membrane bound from internalized insulin was achieved by lowering extracellular pH. At 4 degrees C, 94% of cell-associated radioactivity was membrane bound, whereas at 37 degrees C, in the steady state, 33% was membrane bound and 67% was internalized. There was a significant correlation between membrane-bound insulin and the rate of degradation. These findings reveal that the binding and processing of insulin by the kidney cell line are compatible with the description of the uptake of filtered insulin by the proximal tubule in the intact kidney. Accordingly we conclude that this cell line provides a good model for studying renal epithelial uptake and metabolism of insulin.
A role for insulin in cephalic phase of postprandial thermogenesis in dogs
Authors: Diamond P. , LeBlanc J.
Published: December 2017

The influence of insulin in the cephalic phase of postprandial thermogenesis was investigated in dogs. O2 consumption (VO2) and respiratory quotient (RQ) were continuously monitored 1 h before and 2 h after a 1,015-kcal meal during a control, an atropine, or a pancreatic-denervation experiment. A first phase (cephalic phase) in VO2 increase, lasting at least 50 min, followed by a second phase (digestive phase) were found in the control experiment. During both the atropine and pancreatic-denervation experiment, the first phase of VO2 was inhibited by 52%. The second phase was completely abolished with atropine, whereas it remained comparable to the control in the case of pancreatic denervation. A peak increase for insulin (70 microU/ml over 0 time) was observed 2 min after the onset of feeding in control. It was followed after 25 min by a second increase related to changes in glycemia. Maximal rises of norepinephrine (NE) and epinephrine corresponded to 215 and 120 pg/ml above basal values at 2 min in control experiment. During both atropine and pancreatic denervation the cephalic phase of insulin release was suppressed and the NE increase was inhibited by congruent to 65%. During the digestive phase pancreatic denervation caused an increase in plasma insulin comparable to that of the control, whereas atropine produced no such effect. It is suggested that the cephalic phase of postprandial thermogenesis is mediated through a causal relationship between insulin and NE release.
Indexes of vitamin D deficiency in Japanese quail embryos
Authors: Elaroussi M. A. , Forte L. R. , Biellier H. V. , Eber S. L. , Poelling R. E. , Krause W. J.
Published: December 2017

Effects of vitamin D deficiency (-D) on mineral homeostasis were investigated in Japanese quail embryos. The -D embryos from 1,25(OH)2D3-fed hens became progressively calcium deficient, as documented by hypocalcemia and reduced calcium accumulation by the skeleton, yolk sac, and allantoic fluid. Plasma phosphate was progressively elevated between days 11 and 15. Increased calcium accumulation by the skeleton, yolk sac, and allantoic fluid occurred between days 12 and 15 in +D embryos. Phosphate and adenosine 3',5'-cyclic monophosphate (cAMP) concentrations of allantoic fluid increased in +D embryos during the period of shell calcium mobilization. Further increases in phosphate and cAMP excretion into allantoic fluid occurred in -D embryos, although no calcium was absorbed from the shell. Renal 25(OH)D-1-hydroxylase activity increased between days 11 and 13, whereas the adenylate cyclase response to parathyroid hormone was lost in -D embryos by day 14. These changes in renal function are indicative of secondary hyperparathyroidism in the -D embryos. Differentiation of villus cavity and capillary covering cells occurred in the chorionic epithelium of -D embryos, but eggshell calcium was apparently not absorbed. In contrast, 75% of the total body calcium of newly hatched (+D) chicks was obtained from the eggshell. Thus the dissolution and/or transport of eggshell calcium is dependent on vitamin D in quail embryos.
Abnormalities in systemic norepinephrine kinetics in human congestive heart failure
Authors: Davis D. , Baily R. , Zelis R.
Published: December 2017

A high venous plasma norepinephrine (NE) level is a predictor of poor prognosis in congestive heart failure (CHF). To evaluate the mechanisms responsible for the high plasma NE in CHF, NE kinetics were studied in 19 patients with CHF and 18 normal subjects during a 90-min steady-state intravenous infusion of tracer [3H]NE of high specific activity. Venous plasma NE between 70 and 90 min of infusion was significantly higher in the CHF patients (CHF, 634, and normal, 247 pg/ml; P less than 0.001). The following equations were used: NE clearance = [3H]NE infusion rate (dpm/min)/plasma [3H]NE (dpm/l), and NE spillover = [3H]NE infusion rate (dpm/min)/[3H]NE specific activity (dpm/nmol). In CHF, a decreased clearance and an increased spillover contributed nearly equally to the high plasma NE (NE clearance: CHF, 0.99; normal, 1.48 l.min-1.m-2; P less than 0.001; NE spillover: CHF, 3.60; normal, 2.08 nmol.min-1.m-2; P less than 0.001). These data document that both NE clearance and NE spillover are abnormal in CHF, and they raise the new possibility that the factors responsible for the reduced NE clearance could be related to the factors linking a high plasma NE with early mortality.
Parathyroid hormone depresses cytosolic pH and DNA synthesis in osteoblast-like cells
Authors: Reid I. R. , Civitelli R. , Avioli L. V. , Hruska K. A.
Published: December 2017

It has recently become apparent that a number of hormones and growth factors modulate cytosolic pH (pHi), and there is some evidence that this in turn may influence cell growth. We have examined the effects of parathyroid hormone (PTH) on both these parameters in an osteoblast-like cell line, UMR 106. Preliminary studies, using the pH-sensitive fluorescent probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein indicated that these cells regulate pHi by means of an amiloride-inhibitable Na+-H+ exchanger. Rat PTH-(1-34) (rPTH) caused a progressive dose-related decrease in pHi with a half-maximal effect at 10(-11) M. At 1 h, the maximal depression of pHi was 0.1 +/- 0.01 U. This effect was reproduced by forskolin, but neither agent influenced pHi in the presence of amiloride. Incorporation of [3H]thymidine was reduced by rPTH (half-maximal dose approximately 10(-11) M), forskolin, and N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate. The diacylglycerol analogue, phorbol 12-myristate 13-acetate, increased both pHi and [3H]thymidine incorporation, and amiloride reduced both indexes. However, rPTH remained a potent inhibitor of [3H]thymidine incorporation in the presence of amiloride, even though it did not affect pHi in these circumstances. It is concluded that PTH decreases pHi and growth in UMR 106 cells but that these changes can be dissociated. Depression of pHi may have other important effects on bone metabolism, such as reducing cell-cell communication, and may be associated with alkalinization of the bone fluid compartment.
Sodium balance effects on renin, angiotensinogen, and atrial natriuretic polypeptide mRNA levels
Authors: Iwao H. , Fukui K. , Kim S. , Nakayama K. , Ohkubo H. , Nakanishi S. , Abe Y.
Published: December 2017

The expressions of the renin, angiotensinogen, and atrial natriuretic polypeptide (ANP) genes were studied in rats with varying sodium intakes. mRNAs for angiotensinogen and renin were measured by a sensitive radiodensitometric hybridization assay. ANP mRNA was determined by a dot-blot hybridization assay. In the high-sodium state, plasma renin concentration (PRC), renal renin concentration (RRC), and renal renin mRNA decreased by 88, 90, and 75%, respectively. In the low-sodium state, PRC, RRC, and renin mRNA increased 17-fold, 2.5-fold, and 4.5-fold, respectively. With captopril treatment during sodium depletion, PRC and renin mRNA increased 144-fold and 17.1-fold, respectively, and RRC increased 4.2-fold. The angiotensinogen mRNA level in the liver and kidney decreased in the high-sodium and increased in the low-sodium state to similar extents. Captopril treatment decreased angiotensinogen mRNA in both organs by about half. Plasma ANP and ANP mRNA decreased in the low- compared with the high-sodium state, whereas atrial ANP content was unaltered in both low- and high-sodium states. These results demonstrate that sodium intake affects the expression of the renin and angiotensinogen genes and slightly alters the expression of ANP gene.
Glucocorticoids modulate beta-adrenoceptor subtypes and adenylate cyclase in brown fat
Authors: Scarpace P. J. , Baresi L. A. , Morley J. E.
Published: December 2017

Thermogenesis in brown adipose tissue (BAT) serves as a regulator of body temperature and weight maintenance. Thermogenesis can be stimulated by catecholamine activation of adenylate cyclase through the beta-adrenergic receptor. Glucocorticoids potentiate the action of catecholamines in some tissues by increasing the expression of beta-adrenergic receptors. Paradoxically, glucocorticoids suppress and adrenalectomy enhances BAT thermogenesis. To further study the reasons for this discrepancy, we assessed the effects of methylprednisolone administration, adrenalectomy, and adrenalectomy with corticosterone replacement on adenylate cyclase activity in BAT and on beta-adrenergic receptor density in lungs and BAT of rats. In lungs, the density of the beta 2-adrenergic receptor subtype increases after methylprednisolone administration and decreases after adrenalectomy. There was no change in BAT receptor density, but isoproterenol-, NaF-, and forskolin-stimulated adenylate cyclase activity was reduced by 20–35% after methylprednisolone treatment. There was a two- to threefold increase in adenylate cyclase activity after adrenalectomy, which was reversed by corticosterone administration. These data suggest that one mechanism by which glucocorticoids regulate BAT thermogenesis is by modulating the beta-adrenergic pathway at the level of adenylate cyclase activation.
Role of sialic acid in insulin action and the insulin resistance of diabetes mellitus
Authors: Salhanick A. I. , Amatruda J. M.
Published: December 2017

Adipocytes treated with neuraminidase show markedly reduced responsiveness to insulin without any alteration in insulin binding. In addition, several studies have separately demonstrated both insulin resistance and decreases in membrane sialic acid content and associated biosynthetic enzymes in diabetes mellitus. In the present study, we investigated the role that sialic acid residues may play in insulin action and in the hepatic insulin resistance associated with nonketotic diabetes. Primary cultures of hepatocytes from normal rats treated with neuraminidase demonstrated a dose-dependent decrease in insulin-stimulated lipogenesis. At a concentration of neuraminidase that decreases insulin action by 50%, 23% of total cellular sialic acid content was released. Neuraminidase-releasable sialic acid was significantly decreased in hepatocytes from diabetic rats and this was associated with significant insulin resistance. Treatment of hepatocytes from diabetic rats with cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA) enhanced insulin responsiveness 39%. The enhanced insulin responsiveness induced by CMP-NANA was blocked by cytidine 5'-monophosphate (CMP) suggesting that the CMP-NANA effect was catalyzed by a cell surface sialyltransferase. CMP reduced neuraminidase-releasable [14C]sialic acid incorporation into hepatocytes by 43%. The data demonstrate a role for cell surface sialic acid residues in hepatic insulin action and support a role for decreased cell surface sialic acid residues in the insulin resistance of diabetes mellitus.
Sympathetic nervous system responses to cold exposure and diet in rat skeletal muscle
Authors: Dulloo A. G. , Young J. B. , Landsberg L.
Published: December 2017

Norepinephrine (NE) turnover measured in individual skeletal muscles of the rat assessed sympathetic responses to cold (4 degrees C) and diet. Acute cold exposure increased NE turnover slightly (15–50%) in all muscles examined, including gastrocnemius, tibialis anterior, tensor fascia lata, and soleus, in contrast, cold-accelerated NE turnover in heart by one- to twofold and in interscapular brown adipose tissue (IBAT) by more than threefold. Similar results in skeletal muscle and heart were obtained after 1 wk of cold exposure. Examination of dietary effects on NE turnover, comparing rats fed a sucrose-supplemented diet for 3 days with those fasted for 2 days, indicated that sympathetic activity in skeletal muscle was unresponsive to dietary intake. In heart and IBAT, on the other hand, NE turnover in sucrose-fed rats was twice that obtained in fasted animals. Taken together, the lesser effect of cold and the undetectable response to diet indicate that sympathetic outflow to skeletal muscle is regulated differently than that to heart or IBAT and imply that skeletal muscle is not a major site for sympathetically mediated thermogenic responses to cold exposure or to dietary alteration, such as fasting and sucrose feeding.
Metabolic fate of rat heart endothelial lipoprotein lipase
Authors: Chajek-Shaul T. , Bengtsson-Olivecrona G. , Peterson J. , Olivecrona T.
Published: December 2017

When isolated rat hearts were perfused with medium containing 125I-labeled bovine lipoprotein lipase (LPL), they bound both lipase activity and radioactivity. More than 80% of the bound lipase could be rapidly released by heparin. Low concentrations of bovine LPL displaced 50-60% of the endogeneous, endothelial-bound LPL. Higher concentrations caused additional binding. Both binding and exchange were rapid processes. The hearts continuously released endogenous LPL into the medium. An antiserum that inhibited bovine but not rat LPL was used to differentiate endogeneous and exogeneous LPL activity. When the pool of endothelial LPL was labeled with bovine 125I-labeled LPL and then chased with unlabeled bovine LPL, approximately 50% of the labeled lipase was rapidly displaced. During chase perfusion with medium only, catalytically active bovine LPL appeared in the perfusate. The rate of release was similar to that observed for endogeneous LPL activity and amounted to 10-13% of the heparin-releasable fraction in the first 5 min of perfusion. There was little or no degradation of bovine 125I-labeled LPL to fragments or acid-soluble products. These results indicate that endothelial LPL is accessible for exchange with exogeneous LPL and that detachment rather than degradation may be the pathway for catabolism of endothelial LPL.
[3H]rauwolscine binding to myometrial alpha 2-adrenoceptors in pregnant guinea pig
Authors: Arkinstall S. J. , Jones C. T.
Published: December 2017

Uterine sympathetic nerves can exert an excitatory influence in late pregnancy and during parturition. Neuronal norepinephrine release is increased at these times and a diminished alpha 2-adrenoceptor-mediated prejunctional inhibition could account for this. To assess whether an altered receptor population may contribute, [3H]rauwolscine was used to measure alpha 2-adrenoceptors in myometrial membranes at time intervals throughout pregnancy. High affinity [3H]rauwolscine binding [Kd = 11.4 +/- 1.5 nM (n = 42)] yielded linear Scatchard plots that in nonpregnant myometrium indicated a maximum binding density (Bmax) of 217 +/- 42.4 fmol/mg protein. alpha 2-Adrenoceptor density was increased twofold at midpregnancy (31 days) and thereafter fell sharply by up to 90% toward term (67 +/- 2 days). When uterine growth is accounted for and data are expressed in terms of total myometrial population (uncorrected for plasma membrane recovery), alpha 2-adrenoceptor number was eightfold (midpregnancy) and fourfold (term) greater than the nonpregnant value of 804 +/- 322.4 fmol/uterus. alpha 2-Adrenoceptors were also found to bind dopamine with high affinity [Ki = 3.66 +/- 0.45 microM (n = 3)]. These observations could indicate a pregnancy-related change in uterine sympathetic autoinhibitory capacity and, since alpha 2-adrenoceptors appear also to be located postjunctionally, explain in part reports of altered myometrial responsiveness to norepinephrine infusion and also the uterotonic actions of dopamine.
Physiological hypercortisolemia increases proteolysis, glutamine, and alanine production
Authors: Darmaun D. , Matthews D. E. , Bier D. M.
Published: December 2017

Physiological elevations of plasma cortisol levels, as are encountered in stress and severe trauma, were produced in six normal subjects by infusing them with 140 micrograms.kg-1.h-1 of hydrocortisone for 64 h. Amino acid kinetics were measured in the postabsorptive state using three 4-h infusions of L-[1-13C]leucine, L-[phenyl-2H5]-phenylalanine, L-[2-15N]glutamine, and L-[1-13C]alanine tracers 1) before, 2) at 12 h, and 3) at 60 h of cortisol infusion. Before and throughout the study, the subjects ate a normal diet of adequate protein (0.8 g.kg-1.day-1) and energy intake. The cortisol infusion raised plasma cortisol levels significantly from 10 +/- 1 to 32 +/- 4 micrograms/dl, leucine flux from 83 +/- 3 to 97 +/- 3 mumol.kg-1.h-1, and phenylalanine flux from 34 +/- 1 to 39 +/- 1 (SE) mumol.kg-1.h-1 after 12 h of cortisol infusion. These increases were maintained until the cortisol infusion was terminated (64 h). These nearly identical 15% increases in two different essential amino acid appearance rates are reflective of increased whole body protein breakdown. Glutamine flux rose from 325 +/- 28 to 453 +/- 28 mumol.kg-1.h-1 by 12 h of cortisol infusion and remained elevated at the same level at 64 h. The increase in flux was primarily due to a 55% increase in glutamine de novo synthesis. Alanine flux increased from 207 +/- 13 to 285 +/- 23 mumol.kg-1.h-1 with acute hypercortisolemia and increased further to 475 +/- 59 mumol.kg-1.h-1 at 60 h of cortisol infusion, a result primarily of increased alanine de novo synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Diazoxide unmasks glucose inhibition of insulin release by counteracting entry of Ca2+
Authors: Bergsten P. , Gylfe E. , Wesslen N. , Hellman B.
Published: December 2017

The interaction of diazoxide with the effects of glucose on the insulin-releasing mechanism was analyzed in beta-cell-rich pancreatic islets isolated from ob/ob mice. When added at a concentration of 400 microM to a medium containing 1.28 mM Ca2+, diazoxide converted glucose stimulation of insulin release into inhibition. Further addition of 2 mM theophylline restored the insulin secretory response to glucose. The paradoxical glucose inhibition of insulin release was accounted for by a diazoxide interaction with the entry of Ca2+, unmasking a capacity of the sugar to lower cytoplasmic Ca2+ below its resting concentration.
Distinct receptors for insulin-like growth factor I in rat renal glomeruli and tubules
Authors: Pillion D. J. , Haskell J. F. , Meezan E.
Published: December 2017

Purified preparations of renal glomeruli and tubules were obtained by a procedure involving perfusion of rat kidneys with magnetic iron oxide particles to selectively separate the iron-containing glomeruli from the nonmagnetic tubules. Detergent-soluble extracts of both renal glomerular and tubular membranes showed high-affinity, specific binding of 125I-labeled insulin-like growth factor I (125I-IGF-I), whereas degradation of this peptide hormone was minimal during a 90-min incubation at 22 degrees C in the presence of 2.5 mM EDTA and 5 mM N-ethylmaleimide. The affinity of these receptors for IGF-I appeared identical in the two types of renal tissue, since 50% inhibition of 125I-IGF-I binding to both glomerular and tubular tissue occurred in the presence of approximately 3 x 10(-9) M unlabeled IGF-I. In contrast, insulin was much less effective at blocking 125I-IGF-I binding to either tissue, with 1 x 10(-6) M insulin required to produce 50% inhibition of binding. Relative to 125I-IGF-I binding, 125I-insulin binding to glomerular and tubular tissue was significantly lower per milligram protein. 125I-IGF-I was specifically cross-linked to a glomerular receptor subunit that migrated as two discrete bands with relative molecular weight (Mr) of 140,000-150,000 on sodium dodecyl sulfate polyacrylamide gels in the presence of 40 mM dithiothreitol. In contrast, 125I-IGF-I was cross-linked to a tubular receptor subunit that migrated as two discrete bands but at a slightly different position, with Mr of 120,000-140,000.(ABSTRACT TRUNCATED AT 250 WORDS)
Multiple renin forms in the adrenal gland
Authors: Kim S. H. , Sessler F. M. , Malvin R. L.
Published: December 2017

Renin heterogeneity has been described in rat kidney and plasma. In this study, we used the isoelectric focusing method to 1) characterize the adrenal renin forms in control rats, in rats on low- and high-Na diets, and in nephrectomized rats; and 2) examine their resemblance with plasma renin. Active renin (AR) and inactive trypsin-activatable renin (IR) were measured in adrenal homogenates and plasma. Aliquots were subjected to isoelectric focusing gels. Activation with trypsin (5 mg/ml) was performed before or after isoelectric focusing. Results showed that adrenal glands contained AR and IR. The content of adrenal AR increased significantly only in rats fed a low-Na diet. Following anesthesia, nephrectomy, or high-Na intake, the content of adrenal AR and IR was not significantly changed. In plasma, an inverse relationship between AR and IR was found. Adrenal glands contained six forms of AR focusing at the same pH as those of plasma AR but in different proportions. After activation of IR in adrenal glands, two additional renin forms focusing at pH 6.4 and 6.1 were found, whereas after activation of plasma IR, two peaks focusing at pH 5.9 and 4.8 were significantly enhanced. Adrenal AR forms were modified by alterations of salt and water balance differently than plasma AR. These results support the hypotheses of an endogenous production of renin forms by the adrenal gland.
Calcitonin is a competitive inhibitor of the hydrosmotic effect of oxytocin in toad bladder
Authors: Parisi M. , Ibarra C. , Ladizesky M. , Mautalen C.
Published: December 2017

The effects of calcitonin (CT) on the water transfer in the toad (Bufo arenarum) urinary bladder, an epithelial barrier commonly employed as a model of the mammalian nephron, were studied. The net transmembrane water flux was measured at minute intervals, while the endogenous adenosine 3',5'-cyclic monophosphate (cAMP) levels were determined in isolated epithelial cells. It was observed that 1) CT, up to 10(-6) M, did not have any effect on water permeability. 2) Preincubation with CT, between 10(-7) and 10(-8) M, inhibited the hydrosmotic response to a supramaximal dose of oxytocin (OXT; 2 x 10(-8) M), used here as an antidiuretic hormone (ADH) analogue. This inhibition was reversible and concentration related. Nevertheless, although the magnitude of the response was reduced, its time course of evolution did not change. 3) When CT was added on the previously developed response to OXT, inhibition was also dose dependent with a time course not distinguishable from hormonal washout. 4) CT, up to 10(-6) M, did not modify the hydrosmotic response to 8-bromo cAMP, a potent analogue of the ADH second messenger. 5) CT and OXT increased the intracellular cAMP levels, but both effects were not cumulative. The increase induced by CT plus OXT was significantly lower than the one elicited by OXT alone. It is concluded that CT is a competitive inhibitor to the hydrosmotic effect of OXT in toad urinary bladder. Its action must be located prior to cAMP formation.
Role of interleukin 1 and tumor necrosis factor on energy metabolism in rabbits
Authors: Tredget E. E. , Yu Y. M. , Zhong S. , Burini R. , Okusawa S. , Gelfand J. A. , Dinarello C. A. , Young V. R. , Burke J. F.
Published: December 2017

A study of the combined effects of intravenous infusion of the recombinant cytokines beta-interleukin 1 (IL-1) and alpha-tumor necrosis factor (TNF) on energy substrate metabolism in awake, conditioned, adult rabbits was performed. After a 2-h basal or control period, 48-h fasted rabbits were administered TNF and IL-1 as a bolus (5 micrograms/kg) followed by a continuous intravenous infusion (25 ng.kg-1.min-1) for 3 h. Significant increases in plasma lactate (P less than 0.01), glucose (P less than 0.01), and triglycerides (P less than 0.05) occurred during the combined infusion of IL-1 and TNF, whereas neither cytokine alone had no effect. There was a 33% increase in the rate of glucose appearance (P less than 0.05), but glucose clearance was not altered compared with the control period. Glucose oxidation increased during the combined cytokine infusion period and glucose recycling increased by 600% (P less than 0.002). Lactic acidosis and decreased oxygen consumption, as a result of the cytokine infusions, indicated development of anaerobic glycolytic metabolism. A reduction in the activity state of hepatic mitochondrial pyruvate dehydrogenase (65 vs. 82% in control animals, P less than 0.05) was consistent with the observed increase in anaerobic glycolysis. Thus the combined infusion of IL-1 and TNF in rabbits produces metabolic manifestations seen in severe injury and sepsis in human patients and, as such, may account for the profound alterations of energy metabolism seen in these conditions.
CRF is involved in the pyrogenic and thermogenic effects of interleukin 1 beta in the rat
Authors: Rothwell N. J.
Published: December 2017

Interleukin 1 beta (IL-1 beta) is an endogenous peptide that induces fever, largely by central stimulation of sympathetically mediated thermogenesis. Microinjection (icv) of human recombinant IL-1 beta (50 ng) caused acute (response within 60 min) increases in colonic temperature (1.8 degrees C), oxygen consumption (Vo2; 36%), white blood cell count (96%), and brown adipose tissue (BAT) activity (mitochondrial GDP binding, 129%) in conscious rats. All of these effects were prevented or markedly inhibited by prior injection (icv) of an antagonist to corticotropin-releasing factor (CRF) [alpha-helical CRF-(9-41), 25 micrograms] and reduced by pretreatment with purified antibody to CRF. Injection of endotoxin (2 mg/kg ip), human recombinant tumor necrosis factor-alpha (TNF alpha; 5 micrograms icv) or prostaglandin E2 (PGE2; 100 ng icv) all stimulated body temperature (0.9-1.6 degrees C) and Vo2 (18-25%); TNF alpha did not affect white blood cell count but increased BAT activity by 38%. Prior injection of the CRF antagonist did not modify the actions of endotoxin, TNF alpha, or PGE2. Central injection of CRF (4 micrograms) produced a 23% increase in metabolic rate, which was unaffected by injection of the cycloxygenase inhibitor ibuprofen (5 mg/kg ip). These data indicate that the central effects of interleukin 1 beta on metabolic rate, body temperature, BAT activity, and white blood cell count are all mediated by release of CRF. The thermogenic effects of endotoxin, TNF alpha, and PGE2 are not dependent on CRF.
Effect of exercise on insulin receptor binding and kinase activity in skeletal muscle
Authors: Treadway J. L. , James D. E. , Burcel E. , Ruderman N. B.
Published: December 2017

Insulin action in skeletal muscle is markedly enhanced for several hours after an acute bout of exercise. The purpose of this study was to examine the possible involvement of the intrinsic tyrosine kinase activity of the insulin receptor in mediating these effects. Red and white muscles were removed from rats either at rest or following a treadmill run (45 min at 18 m/min), and insulin receptors were isolated in partially purified form. Basal and insulin-stimulated receptor kinase activity was higher in red than in white muscle, in agreement with previous studies (J. Biol. Chem. 261: 14939-14944, 1986). There was no effect of exercise on insulin binding, basal and insulin-stimulated receptor autophosphorylation, or basal and insulin-stimulated exogenous kinase activity, in either red or white muscle. Similar data were obtained when phosphatase inhibitors were used during receptor isolation. The structure of insulin receptors isolated from the muscle of exercised and control rats was similar as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of affinity cross-linked insulin receptors. We conclude that enhanced insulin action in muscle during the postexercise state is not related to increased kinase activity of the insulin receptor.
Ion microprobe analysis of mouse calvariae in vitro: evidence for a "bone membrane"
Authors: Bushinsky D. A. , Chabala J. M. , Levi-Setti R.
Published: December 2017

It is not clear whether the bone mineral is in passive physicochemical equilibrium with the extracellular fluid (ECF) or is separated from it by a metabolically active partition, a so-called "bone membrane." We used a sensitive high spatial resolution scanning ion microprobe utilizing secondary ion mass spectrometry to compare the relative concentrations of 23Na, 39K, and 40Ca on the surface, subsurface, and cross section of cultured live bone with the concentrations in similar regions of dead bone. Calvariae from neonatal mice were dissected and either incubated for 24 h (live) or subjected to 3 freeze-thaw cycles to kill the bone cells prior to incubation (dead). The live bone has abundant surface Na and K relative to Ca and the Na/K is approximately unity. With dead bone there is a dramatic fall in the K/Ca and an increase in the Na/K. These findings are most consistent with an egress of bone K after cell death. Flux measurements indicate a net influx of Ca into the dead bone. The marked change in relative ion concentrations with cell death indicates that live bone is not in passive physiochemical equilibrium with the surrounding medium. There appears to be a metabolically active partition, a so-called bone membrane, between the mineral and the culture medium that utilizes bone cells to maintain ion gradients.
Galanin release during pancreatic nerve stimulation is sufficient to influence islet function
Authors: Dunning B. E. , Taborsky G. J.
Published: December 2017

To determine if galanin is released during pancreatic neural activation, we measured galanin-like immunoreactivity (GLIR) in pancreatic venous and peripheral arterial plasma during 10 min of electrical stimulation of the mixed autonomic pancreatic nerves in halothane-anesthetized dogs, using a sensitive and specific radioimmunoassay. During mixed pancreatic nerve stimulation (MPNS), pancreatic venous GLIR increased by 174 +/- 20 fmol/ml, whereas arterial GLIR did not change. By use of the arteriovenous concentration difference and measurements of pancreatic venous blood flow, pancreatic spillover of GLIR was calculated and found to increase by 640 +/- 90 fmol/min during MPNS. This MPNS inhibited the output of immunoreactive insulin (IRI; delta = -53 +/- 9%) and somatostatin-like immunoreactivity (SLI, delta = -49 +/- 13%) and stimulated that of immunoreactive glucagon (IRG, delta = +600 +/- 200%). To determine if the amount of GLIR released during MPNS was sufficient to elicit these changes of pancreatic hormone secretion, we compared the effect of MPNS on IRI, SLI, and IRG output with the effect of synthetic galanin infused directly into the pancreatic artery at a rate that reproduced the MPNS-induced spillover of GLIR. Exogenous infusion of synthetic galanin (2.7 pmol/min) increased pancreatic venous levels of GLIR by 169 +/- 38 fmol/ml, did not change arterial GLIR levels, and thus increased calculated spillover (appearance) by 550 +/- 160 fmol/min, which was nearly identical to the increment produced by MPNS. This matched infusion of galanin inhibited IRI (delta = -58 +/- 3%) and SLI output (delta = -35 +/- 3%) and modestly stimulated IRG output (delta = +62 +/- 10%).(ABSTRACT TRUNCATED AT 250 WORDS)
Basis for myocardial mechanical defects associated with non-insulin-dependent diabetes
Authors: Schaffer S. W. , Mozaffari M. S. , Artman M. , Wilson G. L.
Published: December 2017

Hearts isolated from 12-mo non-insulin-dependent diabetic rats exhibited reduced rates of contractility and relaxation. Associated with the abnormality in contractility was a redistribution in myosin isozyme content to the least active V3 form. Defects in myocardial relaxation also occurred concomitantly with impaired handling of calcium. Total tissue calcium content rose 35% in the diabetic hearts. At the same time, the activity of the pump responsible for maintaining normal cytoplasmic calcium levels was reduced. At a free calcium concentration of 2.0 microM, the rates of sarcoplasmic reticular calcium uptake and adenosinetriphosphatase activity of the diabetic hearts were decreased approximately 30%. Diastolic ventricular stiffness increased dramatically. The net result of these abnormalities in calcium metabolism is a significant impairment in mechanical performance of the diabetic heart.
Effects of low-sodium diet on regulation of platelet alpha 2-adrenergic receptors in young and elderly humans
Authors: Supiano M. A. , Neubig R. R. , Linares O. A. , Halter J. B. , Rosen S. G.
Published: December 2017

To examine whether there are age differences in agonist-mediated alpha 2-adrenergic receptor (alpha 2-AR) regulation, we studied the effect of a sustained increase in plasma norepinephrine (pNE) during a 7-day 10-meq Na+/day diet on platelet alpha 2-AR binding and its linked adenylate cyclase (AC) activity in 11 elderly and 11 young healthy subjects. In the young, a 41% increase in mean pNE after a low-sodium diet was correlated with a decline in receptor density (Bmax; r = -0.816; P less than 0.01) and was accompanied by a reduction in the maximal percent inhibition of sodium fluoride-stimulated AC activity by epinephrine (%AC INH; 33 +/- 4 vs. 24 +/- 4%, mean +/- SE; P less than 0.05 vs. normal diet). Despite a comparable 39% increase in mean pNE in the elderly, neither Bmax nor %AC INH was significantly reduced after a low-sodium diet. The amount of pertussis toxin substrate (Gi protein) was similar in both groups before and after dietary sodium restriction. At comparable pNE, %AC INH in the groups was similar (young, 24 +/- 4 vs. elderly, 18 +/- 4%; P = NS). We postulate that higher basal pNE levels in the elderly on normal diet may account for the lack of further downregulation of platelet alpha 2-AR density and response after low-sodium diet.
Hepatic sexual dimorphism: ontogeny and influence of adult gonadectomy
Authors: Studer R. K. , Ganas L.
Published: December 2017

The ontogeny of alpha 1- and beta-adrenergic receptors and their relative stimulation of phosphorylase alpha activity in hepatic tissue from male and female rats were compared. A decrease in beta-adrenergic receptor concentration and 4-(t-butylamino-2-hydroxypropoxy)-[5,7-3H]benzimidazol-2-one HCl affinity for these sites was found in males and females, when data from membranes of 20- to 22-day animals was compared with that from neonates. No subsequent decline in receptor concentration was noted in the female; however, the beta-mediated phosphorylase activation was further diminished by 49-56 days, suggesting maturational changes beyond the receptor-adenylate cyclase system. Although high-affinity beta-adrenergic receptors were documented in membranes from pubertal males, they were not identified on the intact cells, and activation of phosphorylase alpha via the beta-pathway was minimal. This suggests the majority of the beta-receptors are sequestered in cellular sites not accessible to the hydrophilic ligand or epinephrine in the sexually mature male. Ontogeny of the alpha 1-adrenergic receptors was similar in males and females. Gonadectomy of mature males and females did not eliminate the sexual differences in adrenergic response. However, the ovariectomized females developed an enhanced basal and alpha-adrenergic stimulated phosphorylase activity. The rise in cytosolic free calcium in response to epinephrine was increased in the ovariectomized females to values seen in the intact male, whereas the response in the castrate male was depressed. The results suggest the dimorphism in alpha 1- and beta-adrenergic receptor function is determined by factors other than the ambient concentration of sex steroids in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)
Kinetics of zinc metabolism in the rat: effect of dibutyryl cAMP
Authors: Dunn M. A. , Cousins R. J.
Published: December 2017

N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (Bt2cAMP) administration to rats is shown to reduce serum zinc levels and increase liver zinc and metallothionein significantly. Such redistribution is similar to that seen in the acute phase response to stress. To determine the sites of regulation of zinc metabolism involved in zinc redistribution, we compared the kinetics of intravenously administered 65Zn between control and Bt2cAMP-treated rats. 65Zn disappeared more rapidly from the plasma of Bt2cAMP rats, whereas 65Zn content of liver and liver metallothionein was increased. 65Zn in spleen and bone marrow also increased. No change was seen in muscle or kidney, and 65Zn content decreased in skin, bone, small intestine, and feces. These kinetic data were integrated into two compartmental models describing zinc metabolism in control and Bt2cAMP-treated states. Models were constructed using the SAAM and CONSAM modeling programs. Comparison of models suggest several sites of regulation due to Bt2cAMP. Zinc uptake into liver metallothionein from both plasma and other zinc pools within the liver was increased, whereas the release of metallothionein-bound zinc to plasma decreased. These changes increased liver zinc at the expense of plasma zinc, tissue zinc (principally skin, bone, and small intestine), and fecal zinc excretion. Bone marrow, spleen, and muscle were protected against zinc loss due primarily to decreased rates of tissue zinc loss. It was also postulated that Bt2cAMP increased the transfer of liver zinc to secreted alpha 2-macroglobulin. These results demonstrate that Bt2cAMP-induced zinc redistribution is tissue specific and related in part to metallothionein synthesis.
Characterization of calcium channels of a glucose-responsive rat insulinoma
Authors: Hoenig M. , Russo L. L. , Ferguson D. C.
Published: December 2017

Voltage-dependent calcium channels are important in the control of calcium influx into excitable cells. With the use of cells isolated from a glucose-responsive rat insulinoma, the effect of the calcium-channel blocker nitrendipine on insulin release was examined. When 50 nM nitrendipine was added with a stimulatory glucose concentration (30 mM), first-phase insulin release was preserved, whereas the second phase was inhibited by 39.4 +/- 5.3%. When 50 nM nitrendipine was also present during basal and stimulated insulin release, the insulin release from fresh cells was significantly less during both phases compared with cells not exposed to nitrendipine (P less than 0.05). In cells cultured for 1 day in 30 mM glucose, a diminished insulin response was seen on stimulation with 30 mM glucose. Nitrendipine (50 nM) did not lead to a further decrease in insulin release. Saturable binding sites in homogenate, whole cells, and purified plasma membranes prepared from the insulinoma were characterized using [3H]nitrendipine. The Kd (in pM) for homogenate from uncultured cells was 225 +/- 34 (n = 11), whereas the Bmax (in fmol/mg protein) was 52 +/- 5. The number of apparent binding sites for [3H]nitrendipine was reduced by approximately 50% in cultured cells (Bmax = 30 +/- 5 fmol/mg protein). The reduction in insulin release from cultured cells correlated well with the reduction in nitrendipine binding. It is concluded that the decrease in the number of apparent binding sites for nitrendipine after culture represents a reduction in functional calcium channels associated with influx of calcium and insulin release.
Vasopressin: a regulator of adrenal glucocorticoid production?
Authors: Brooks V. L. , Blakemore L. J.
Published: December 2017

Vasopressin infusion has been shown to decrease plasma adrenocorticotropic hormone (ACTH) concentration and transiently increase plasma cortisol concentration in conscious dogs. In the present study, one experiment tested the hypothesis that vasopressin infusion decreases ACTH by activation of a V1 receptor mechanism, e.g., by increasing atrial pressures and stimulating the low-pressure baroreceptor reflex. Administration of a vasopressin V1 antagonist eliminated the increases in atrial pressure and decreases in heart rate with vasopressin infusion (1 ng.kg-1.min-1), as it eliminated the decrease in ACTH, which is consistent with baroreflex-mediated inhibition of ACTH by vasopressin. A second experiment evaluated the role of ACTH in the increase in glucocorticoids. Dexamethasone pretreatment, which inhibits ACTH secretion, abolished the increase in glucocorticoid concentration with vasopressin infusion, indicating that ACTH is necessary for the glucocorticoid response. A third experiment was performed to determine whether the glucocorticoid response could be restored in dexamethasone-treated dogs, when ACTH concentration was maintained near control levels by intravenous infusion of synthetic alpha-ACTH-(1-24) (0.3 ng.kg-1.min-1). In these dogs, vasopressin infusion produced a sustained increase in plasma glucocorticoid concentration from 22 +/- 3 to 49 +/- 8 ng/ml (P less than 0.001). Infusing higher levels of ACTH (0.5 ng.kg-1.min-1) enhanced basal glucocorticoid levels but did not enhance the response to vasopressin. Vasopressin infusion did not alter clearance of glucocorticoids. Collectively, these results suggest that vasopressin directly stimulates adrenal glucocorticoid production, provided that background levels of ACTH are present.