bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium response of single adrenal glomerulosa cells to external potassium
Authors: Quinn S. J. , Williams G. H. , Tillotson D. L.
Published: December 2017

The cytosolic calcium (Cai2+) response to external potassium (K+) was examined in single rat zona glomerulosa (ZG) cells by monitoring fura-2-fluorescence with microspectrofluorometry and digital imaging microscopy. The majority (68%) of morphologically identified ZG cells demonstrated an increase in Cai2+ during K+ stimulation. Cai2+ rose monotonically from a mean basal level of 232 +/- 15 to 285 +/- 37 nM at 5 mM and 680 +/- 60 nM at 10 mM K+ for responsive ZG cells. The Cai2+ response was largely (greater than 90%) inhibited by nominal zero calcium or 1 mM cadmium and substantially modified in the presence of 10(-5) M nifedipine. The response kinetics were characterized by a rising phase that depended on the size of the Cai2+ change, with larger increases associated with a faster onset. Cai2+ approached a plateau level that was sustained for the duration of K+ stimulation from 1 to 5 min. Cai2+ appeared to be more uniformly distributed across the cell under resting conditions than during stimulation. Assessment of the Cai2+ response in single ZG cells documents 1) a majority, but not all, of ZG cells respond to K+, 2) simple kinetics consisting of a rapid onset and sustained plateau Cai2+ level, 3) a dose-dependent Cai2+ increase in the physiological range of K+, and 4) inhibition by calcium channel blockers and sensitivity to small increases in K+ consistent with activation of low-threshold calcium channels.
Induction of mRNA for IGF-I and -II during growth hormone-stimulated muscle hypertrophy
Authors: Turner J. D. , Rotwein P. , Novakofski J. , Bechtel P. J.
Published: December 2017

The expression of insulin-like growth factor (IGF) genes during skeletal and cardiac muscle hypertrophy was examined using skeletal and cardiac muscle hypertrophy was examined using adult 5-mo-old female Wistar-Furth rats implanted with growth hormone-secreting GH3 cells. Control and treated animals were killed at 40, 60, and 80 days after initiation of the experiment. From the time of injection to day 80, body, heart, skeletal muscle, and liver weights increased 112, 93, 55, and 314%, respectively. RNA was extracted and steady-state levels of IGF-I and IGF-II mRNAs were quantitated using a solution-hybridization nuclease-protection assay. Low levels of mRNA for both growth factors were detected in control tissues. By day 80 IGF-I mRNA had increased eightfold and IGF-II mRNA sixfold in skeletal muscle from treated rats. In cardiac muscle the levels of mRNA for both growth factors rose three- to fourfold. Although growth hormone induced an increase in hepatic IGF-I mRNA, IGF-II mRNA remained nearly undetectable. This study shows that during growth hormone-stimulated muscle growth mRNAs for both IGF-I and IGF-II accumulate, supporting other observations implicating the IGFs as paracrine or autocrine factors involved in skeletal muscle growth.
Metallothionein response to stress in rats: role in free radical scavenging
Authors: Hidalgo J. , Campmany L. , Borras M. , Garvey J. S. , Armario A.
Published: December 2017

The possibility that liver metallothionein (MT) can function as an antioxidant in vivo has been studied in the rat. It was found that the stress of food and water deprivation with or without physical immobilization consistently increased liver lipid peroxidation (LLP), suggesting that liver MT induction by stress might be related to the stress-induced LLP. This was supported by results with the lipid peroxidation promoter dimethyl sulfoxide (DMSO) and the natural antioxidant vitamin E. Whereas DMSO administration increased LLP levels in basal and stress situations, vitamin E decreased them. Liver MT levels were increased by DMSO in basal and stress situations, whereas they were decreased by vitamin E during stress. These in vivo results are consistent with an antioxidant role of liver MT suggested by previous in vitro results. However, liver MT preinduction by Zn treatment did not result in a lower MT response to stress. Instead a positive synergistic effect between Zn and stress appeared to be present. This result indicates that the mechanism of action of MT as antioxidant remains unclear.
Importance of glycosylation for hepatic clearance of renal renin
Authors: Kim S. , Hiruma M. , Ikemoto F. , Yamamoto K.
Published: December 2017

Three differently glycosylated forms of renin (renin A, B-1, and B-2) were highly purified from rat kidneys by pepstatin-aminohexyl-Sepharose affinity chromatography and by serial lectin affinity chromatography on concanavalin A (con A) and lentil lectin-Sepharose, and the role of glycosylation of renin was investigated. Renin A and renin B-1 were loosely and tightly bound to con A, respectively, but did not bind to lentil lectin. Renin B-2 bound to both con A and lentil lectin. These three forms of renin were all similar in their physicochemical characteristics, including molecular weight, isoelectric point, specific activity, Km, optimum pH, and antigenicity. Each form of renin, labeled with 125I and given intravenously to anesthetized rats, disappeared from the circulation at different rates (metabolic clearance rates of 5.05 +/- 1.02, 17.1 +/- 2.5, and 36.0 +/- 4.1 ml.min-1.kg-1 for renins A, B-1, and B-2, respectively). Labeled renin A distributed to a similar extent in the liver and kidney (21.2 +/- 0.2 and 15.2 +/- 0.8% of the injected dose, respectively), whereas renins B-1 and B-2 were distributed predominantly in the liver (56.3 +/- 1.2 and 72.3 +/- 3.7% of the injected dose, respectively) and to a lesser extent in the kidney (4.3 +/- 0.3 and 2.1 +/- 0.2%, respectively). Deglycosylation of renin B-1 with endoglycosidase F resulted in no loss of its enzymatic activity or antigenicity but greatly reduced the metabolic clearance rate to 18% (from 17.1 +/- 2.5 to 3.09 +/- 0.17 ml.min-1.kg-1). Deglycosylation of renin B-1 greatly decreased its uptake by the liver (from 56.3 +/- 1.2 to 3.3 +/- 0.2%) and increased its uptake by the kidney (from 4.3 +/- 0.3 to 23.9 +/- 0.9%). These studies indicate the importance of glycosylation of renin for its hepatic uptake and metabolic clearance rate.
PTH elevates inositol polyphosphates and diacylglycerol in a rat osteoblast-like cell line
Authors: Civitelli R. , Reid I. R. , Westbrook S. , Avioli L. V. , Hruska K. A.
Published: December 2017

Parathyroid hormone (PTH)-stimulated signal transduction through mechanisms alternate to adenosine 3',5'-cyclic monophosphate (cAMP) production were studied in UMR 106-01 cells, a cell line with an osteoblastic phenotype. PTH produced transient, dose-related increases in cytosolic calcium [( Ca2+]i), inositol trisphosphates, and diacylglycerol (DAG). Both inositol 1,4,5-trisphosphate (Ins-1,4,5P3) and inositol 1,3,4-trisphosphate (Ins-1,3,4P3) production were rapidly stimulated by PTH. Consistent with the production of Ins-1,3,4P3, rapid stimulation of late eluting inositol tetrakisphosphate was observed. The effects on the inositol phosphates were induced rapidly, consistent with roles as signals for changes in [Ca2+]i. In saponin-permeabilized UMR 106-01 cells, Ins-1,4,5P3 stimulated 45Ca release from a nonmitochondrial intracellular pool. Thus the hypothesis that PTH-stimulated Ins-1,4,5P3 production initiates Ca2+ release and contributes to transient elevations of [Ca2+]i is supported. Pretreatment of UMR 106-01 cells with pertussis toxin had no effect on PTH stimulation of inositol phosphates. Pertussis toxin reduced PTH-stimulated elevations of [Ca2+]i, but cAMP analogues had an even greater effect than pertussis toxin. These data suggest that stimulation of cAMP production during PTH stimulation may negatively affect production of rises in [Ca2+]i during PTH stimulation. The inactivation of the inhibitory G protein of adenylate cyclase by pertussis toxin could explain its action similar to cAMP analogues. Cyclic nucleotides diminish the effects of PTH on [Ca2+]i, probably interacting on a biochemical step subsequent to or independent of Ins-1,4,5P3 release.
Hydrocortisone secretion: production rate and pulse characterization by numerical deconvolution
Authors: Toutain P. L. , Laurentie M. , Autefage A. , Alvinerie M.
Published: December 2017

Based on serial blood sampling over 24 h, hydrocortisone was shown to be secreted episodically in the horse. The purpose of the present experiment was to characterize peaks and troughs by analyzing the instantaneous secretion rate profile obtained by a deconvolution technique rather than from the plasma concentration time profile. Kinetic parameters of hydrocortisone were determined following intravenous bolus and intravenous perfusion of hydrocortisone. Stationary and nonlinearity of hydrocortisone disposition were demonstrated. With the use of clearance values calculated from constant perfusion administration, the 24-h hydrocortisone production rate was estimated at 0.46 +/- 0.08 mg.kg-1.24 h-1. The instantaneous secretory profile was reconstituted by deconvoluting the plasma concentration profile using structural parameters determined from the bolus hydrocortisone administration. When this secretory profile was subjected to a pulse analysis program, the number of detected peaks was found to be 17.25 +/- 1.26 and the mean peak duration 34.01 +/- 5.52 min. The total duration of secretory activity was estimated at 582.5 +/- 63.97 min. By comparison, when the plasma concentration profile was analyzed directly, the number of peaks was only 10.0 +/- 1.41 but their mean duration was much longer, i.e., 105.25 +/- 21.24 min. The origin of these differences and the advantages and limits of deconvolution analysis are discussed.
Discrepancy between glucose transport and transporters in human femoral adipocytes
Authors: Karnieli E. , Moscona R. , Rafaeloff R. , Illouz Y. G. , Armoni M.
Published: December 2017

Obesity is known to be associated with insulin resistance in human and rat adipocytes. However, it is not known what are the perturbations in insulin action that contribute to disproportional femoral obesity. Thus femoral subcutaneous adipose tissue was obtained from lean women with various degrees of disproportional obesity, by liposuction. 3-O-methylglucose (3-O-methyl-D-glucopyranose) transport was measured in intact cells, and glucose transporter levels in plasma and low-density microsomal membranes were assessed using the cytochalasin B binding assay. A sixfold cellular enlargement was associated with increase in both basal and insulin-stimulated glucose transport activity in the intact cell, and a 300-600% increase in insulin stimulating effect per se. However, when glucose transporter levels were assessed, this cellular enlargement was accompanied by a 40-70% transporter depletion (in largest cells compared with smallest ones) in both subcellular fractions examined, from either basal or insulin-stimulated cells. This discrepancy, between increasing cellular glucose transport rates and relative depletion of transporter levels, suggests that these cells are not insulin resistant, as could be expected from their large size. A role for other factor(s), additional to glucose transporter levels, in the regulation of cellular glucose uptake rate is thus suggested.
Effect of epoxyeicosatrienoic acids on growth hormone release from somatotrophs
Authors: Snyder G. D. , Yadagiri P. , Falck J. R.
Published: December 2017

Growth hormone secretion was stimulated in vitro by products of arachidonic acid epoxygenase, the epoxyeicosatrienoic acids. 5,6-Epoxyeicosatrienoic and 14,15-epoxyeicosatrienoic acid stimulated growth hormone release from an enriched population of somatotrophs (approximately 85%) by twofold. Inhibition of arachidonic acid metabolism by indomethacin did not affect growth hormone-releasing hormone stimulation of growth hormone release. In contrast, pretreatment of somatotrophs with an 11,12-isonitrile analogue of arachidonic acid that inhibits arachidonic acid epoxygenase, resulted in a 20-25% inhibition of growth hormone-releasing hormone-stimulated growth hormone release. 14,15-Epoxyeicosatrienoic acid stimulated a concentration-dependent increase (twofold) in the cytoplasmic concentration of adenosine 3',5'-cyclic monophosphate (cAMP) in the somatotrophs. 14,15-Epoxyeicosatrienoic acid also rapidly increased the intracellular free calcium concentration in somatotrophs from resting levels (approximately 80 nM) to greater than 250 nM. Growth hormone-releasing hormone increased the free intracellular calcium to 160-180 nM. Preincubation of somatotrophs with somatostatin inhibited growth hormone-releasing hormone-stimulated growth hormone secretion, cAMP accumulation, and 14,15-epoxyeicosatrienoic acid stimulated cAMP accumulation. These data are suggestive that the epoxyeicosatrienoic acids may have a role in the secretion of growth hormone.
Calcitonin gene-related peptide receptor antagonist human CGRP-(8-37)
Authors: Chiba T. , Yamaguchi A. , Yamatani T. , Nakamura A. , Morishita T. , Inui T. , Fukase M. , Noda T. , Fujita T.
Published: December 2017

From this study, we predicted that the human calcitonin gene-related peptide (hCGRP) fragment hCGRP-(8-37) would be a selective antagonist for CGRP receptors but an agonist for calcitonin (CT) receptors. In rat liver plasma membrane, where CGRP receptors predominate and CT appears to act through these receptors, hCGRP-(8-37) dose dependently displaced 125I-[Tyr0]rat CGRP binding. However, hCGRP-(8-37) had no effect on adenylate cyclase activity in liver plasma membrane. Furthermore, hCGRP-(8-37) inhibited adenylate cyclase activation induced not only by hCGRP but also by hCT. On the other hand, in LLC-PK1 cells, where calcitonin receptors are abundant and CGRP appears to act via these receptors, the bindings of 125I-[Tyr0]rat CGRP and 125I-hCT were both inhibited by hCGRP-(8-37). In contrast to liver membranes, interaction of hCGRP-(8-37) with these receptors led to stimulation of adenosine 3',5'-cyclic monophosphate (cAMP) production in LLC-PK1 cells, and moreover, this fragment did not inhibit the increased production of cAMP induced not only by hCT but also by hCGRP. Thus hCGRP-(8-37) appears to be a useful tool for determining whether the action of CGRP as well as that of CT is mediated via specific CGRP receptors or CT receptors.
Cytosolic free calcium in normal somatotropes: effects of forskolin and phorbol ester
Authors: Holl R. W. , Thorner M. O. , Leong D. A.
Published: December 2017

Digital imaging microscopy using the calcium-sensitive indicator probe fura-2 was combined with a reverse hemolytic plaque assay (RHPA) for growth hormone (GH) secretion. This technique allows dynamic measurements of the cytosolic free calcium concentration ([Ca2+]i) in individual pituitary somatotropes. Stimulation by growth hormone-releasing factor (GRF) increases, whereas somatostatin (SRIF) reduces [Ca2+]i in this cell type. [Ca2+]i increased in somatotropes when the cellular content of adenosine 3',5'-cyclic monophosphate (cAMP) was elevated by 1) activating cellular adenylate cyclase with forskolin (5 microM) and 2) treatment with the cAMP-analogues dibutyryl-cAMP (1 mM) or 8-bromo-cAMP (5 mM). The forskolin-induced calcium rise was abolished in the absence of extracellular calcium. This indicates that cAMP increases the influx of calcium into the cytosol and thereby stimulates hormone release. When forskolin was given in combination with SRIF (10 nM), [Ca2+]i decreased to the same level reached with SRIF treatment alone, indicating a site of action distal to the generation of cAMP. Activating protein kinase C with the phorbol ester 12,13-phorbol dibutyrate (PDB; 100 nM) increased [Ca2+]i as well. Again, this effect was dependent on extracellular calcium and blocked when PDB and SRIF were applied simultaneously. Combined stimulation with GRF plus PDB did not augment the response of [Ca2+]i over GRF treatment alone.
1,25-Dihydroxyvitamin D3 restores fertility of vitamin D-deficient female rats
Authors: Kwiecinksi G. G. , Petrie G. I. , DeLuca H. F.
Published: December 2017

Vitamin D deficiency reduces mating success and fertility in female rats, but it is not known if the reduction in reproductive performance is a direct action of vitamin D or the hypocalcemia associated with vitamin D deficiency. The effect of vitamin D deficiency with normocalcemia on fertility and reproductive capacity in female rats was investigated. Female weanling rats were maintained on vitamin D-deficient or vitamin D-replete diets until maturity and mated to age-matched, normal, vitamin D-replete males. Three groups of vitamin D-deficient females were maintained on diets varying in calcium and Pi concentrations to test the effect of vitamin D deficiency with different serum calcium and Pi concentrations on reproductive performance. Vitamin D-deficient females were capable of reproduction, but successful matings by all groups of vitamin D-deficient females were markedly reduced regardless of serum calcium concentration, when compared with matings with vitamin D-replete females. Fertility was also drastically reduced in litters from all groups of vitamin D-deficient females regardless of serum calcium concentration, when compared with litters from vitamin D-replete females. Vitamin D-deficient female rats that received vitamin D or 1,25-dihydroxyvitamin D3 were capable of successfully mating and giving rise to normal, healthy litters. These results indicate that vitamin D and not hypocalcemia is directly responsible for reduced reproductive capacity and fertility in vitamin D-deficient female rats.
Anti-calmodulin agents affect osmotic and angiotensin II-induced vasopressin release
Authors: Rossi N. F. , Schrier R. W.
Published: December 2017

Calcium ions and particularly calcium influx play a crucial part in initiating the intracellular events that result in arginine vasopressin (AVP) release to both osmotic and nonosmotic stimuli. Calmodulin appears to modulate the effects of calcium on synaptic transmission and hormone release in other systems. This study tested the effects of three distinct classes of anti-calmodulin agents on the release of AVP to either a rise in osmolality of 20 mosmol/kg water or to 1 X 10(-5) angiotensin II (ANG II) in cultured hypothalamo-neurohypophysical complexes. Micromolar concentrations of R 24571, the active naphthalenesulfonamides, W 7 and W 13, and trifluoperazine (TFP) inhibited AVP release to osmotic stimulation. In contrast, W 5, a severalfold less active anti-calmodulin agent, had no effect on osmotically stimulated AVP release. The active naphthalenesulfonamides, but not R 24571 or TFP, blocked release of AVP to ANG II. In contrast, neither R 24571 nor TFP inhibited AVP release to ANG II stimulation. Collectively, the data demonstrated a dissociation between inhibition of AVP release and the anti-calmodulin properties of the drugs, thereby suggesting that nonspecific actions masked the calmodulin-blocking effects of the drugs or that the inhibition occurred by some alternative mechanism(s).
Calcium stimulates the release of calcitonin gene-related peptide from the canine thyroid
Authors: Ahren B. , Ekman R. , Laurberg P.
Published: December 2017

The calcitonin gene in the thyroid parafollicular cells generates two different mRNAs, which encode for the precursors of calcitonin and calcitonin gene-related peptide (CGRP). In this study, we investigated whether these two peptides are released simultaneously in the perfused dog thyroid. The isolated dog thyroid (n = 10) was once-through perfused with a Krebs-Ringer bicarbonate buffer. After elevation of the buffer Ca2+ concentration from 1.5 to 2.5 mM, a rapid, marked, and parallel secretion of both calcitonin and CGRP occurred (P less than 0.001). By stepwise increase of the buffer Ca2+ concentration, it was found that, although an elevation from 1.5 to 1.65 mM had no influence on the thyroid output of calcitonin or CGRP, elevations to 1.75, 2.0, and 2.5 mM of Ca2+ induced dose-dependent parallel increases in the thyroid output of calcitonin and CGRP. Furthermore, the stimulation with pentagastrin (100 pM) increased the thyroid output of both calcitonin and CGRP in parallel. It is concluded that the normal dog thyroid releases calcitonin and CGRP in parallel on stimulation with Ca2+ and pentagastrin.
Insulin, glucagon, and catecholamines in prevention of hypoglycemia during fasting
Authors: Boyle P. J. , Shah S. D. , Cryer P. E.
Published: December 2017

To dissect the mechanisms of the prevention of hypoglycemia during fasting, eight normal humans were studied after overnight and 3-day fasts. Prolonged fasting resulted in the expected decrements in base-line glucose production and plasma glucose, insulin, and C-peptide and increments in plasma glucagon, epinephrine, norepinephrine, growth hormone, and cortisol. After the overnight and 3-day fasts, insulin restoration (0.2 mU.kg-1.min-1) alone resulted in transient decrements in glucose production and only 15 and 19% decrements in plasma glucose, respectively. Selective glucagon deficiency (somatostatin infusion with insulin and growth hormone replacement) resulted in transient decrements in glucose production and additional 24 and 29% decrements in plasma glucose, respectively. Notably, plasma glucose plateaued under both fasting conditions in both instances. Combined alpha- and beta-adrenergic blockade (phentolamine and propranolol infusions) alone had no effect on glycemia under either fasting condition. However, progressive hypoglycemia developed during adrenergic blockade coupled with glucagon deficiency after the overnight fast (85 +/- 2 to 48 +/- 4 mg/dl, P less than 0.001) and after the 3-day fast (65 +/- 2 to 33 +/- 1 mg/dl, P less than 0.001). These were the result of both decrements in glucose production and increments in glucose clearance. Thus we conclude that during fasting 1) the prevention of hypoglycemia is not due solely to decreased insulin secretion. 2) Glucagon plays a primary counterregulatory role. Sympathochromaffin catecholamines are not normally critical but compensate and become critical when glucagon is deficient. Adrenomedullary epinephrine is probably the relevant catecholamine. 3) Other hormones, neurotransmitters, or substrate effects may, or may not, be involved; if they are, they appear to stand low in the hierarchy of glucoregulatory factors.
Lipoprotein lipase in myocytes and capillary endothelium of heart: immunocytochemical study
Authors: Blanchette-Mackie E. J. , Masuno H. , Dwyer N. K. , Olivecrona T. , Scow R. O.
Published: December 2017

Lipoprotein lipase was immunolocalized by electron microscopy in hearts of young mice; 78% of lipoprotein lipase was in myocytes, 3-6% in extracellular space, and 18% in capillary endothelium. Lipoprotein lipase in myocytes was located primarily in sarcoplasmic reticulum, Golgi sacs, and transport vesicles and also in secretory vesicles at the cell periphery. Lipoprotein lipase in extracellular space was present near the orifice of secretory vesicles of myocytes and in narrow zones spanning the space between myocytes and capillary endothelium. The lowest concentration of lipase associated with endothelial cells was at the basal plasma membrane, whereas the highest concentration was at the surface of luminal projections. Lipoprotein lipase was associated with chylomicrons at the capillary surface but not with chylomicron remnants. Fasting mice for 48 h increased, in heart, lipoprotein lipase activity by 120% and immunolocalized lipase by 270%. The greatest increase (5-fold) occurred at the surface of intraluminal endothelial projections. The findings indicate that lipoprotein lipase in heart is synthesized by myocytes, transferred across extracellular space along cell surfaces and across endothelial cells via vesicles or intracellular channels, and concentrated at the surface of luminal projections of endothelium where the enzyme hydrolyzes triacylglycerol of chylomicrons and very low-density lipoproteins.
Effect of 7 days of bed rest on dose-response relation between plasma glucose and insulin secretion
Authors: Mikines K. J. , Dela F. , Tronier B. , Galbo H.
Published: December 2017

Physical training decreases glucose-stimulated insulin secretion. To further explore the influence of the level of daily physical activity on beta-cell secretion, the effect of 7 days of bed rest was studied in six young, healthy men by sequential hyperglycemic clamp technique (7, 11, and 20 mM glucose, each step lasting 90 min). At 11 and 20 mM glucose, insulin concentrations in plasma were higher after (87 +/- 11 and 303 +/- 63 microU/ml) than before (63 +/- 5 and 251 +/- 50 microU/ml, P less than 0.05) bed rest. Also C-peptide levels were higher after bed rest than before during glucose stimulation. The responses of other hormones, metabolites, or electrolytes influencing beta-cell secretion were not influenced by bed rest. In spite of increased insulin levels after bed rest, glucose disposal at 20 mM of glucose was significantly lower after bed rest than before. It is concluded that bed rest for 7 days increases the glucose-stimulated insulin response, at least partly due to a beta-cell adaptation increasing glucose-stimulated insulin secretion. However, the insulin secretion does not increase adequately compared with the peripheral insulin resistance induced by bed rest.
Role of T3 in thermogenic and trophic responses of brown adipose tissue to cold
Authors: Park I. R. , Mount D. B. , Himms-Hagen J.
Published: December 2017

Cold-induced growth of brown adipose tissue (BAT) was studied in thyroidectomized rats that received low doses of either thyroxine (T4) or 3,5,3'-triidothyronine (T3). The objective was to find out whether the cold-induced increase in activity of T4 5'-deiodinase, and thus increased endogenous T3 generation in BAT itself, was necessary for growth of BAT or whether T3 from the blood could serve as effectively as T3 produced endogenously. The acute thermogenic response of BAT to cold (15 h at 4 degrees C), as measured by the increase in mitochondrial GDP binding, was abolished by thyroidectomy, as seen previously, and restored by T3 as well as by T4 treatment. The long-term trophic response to cold (20–25 days at 4 degrees C), as indicated by increases in protein and DNA and in mitochondrial concentrations of GDP-binding sites and uncoupling protein, occurred whether T3 or T4 was administered to these thyroidectomized rats. We conclude that endogenous T3 production in BAT does not direct and is not essential for the long-term trophic response of this tissue to cold. We are not able to exclude, on the basis of the present results, that an optimal growth rate during the initial phase of the trophic response may require enhanced endogenous production of T3 in BAT. The cold-induced increase in T4 5'-deiodinase activity, presumably mediated by an action of norepinephrine, does not require the presence of either T3 or T4, as seen previously by others.
Adrenalectomy prevents obesity in glutamate-treated mice
Authors: Tokuyama K. , Himms-Hagen J.
Published: December 2017

Mice treated with monosodium glutamate (MSG) in the neonatal period grow into obese, stunted adults without overeating. We have previously demonstrated normal control of brown adipose tissue (BAT) thermogenic function in the MSG-treated mouse and have concluded that thermoregulation at a lower than normal body temperature for most of the time is a major cause of its obesity. The objective of the present experiments was to find out whether adrenalectomy would prevent obesity in the MSG-treated mouse, as it does in hyperphagic obese rodents, and whether the thermoregulatory anomaly would be prevented by this procedure. MSG-treated mice that were adrenalectomized at 5 wk of age and studied at 10 wk of age did not become obese. Adrenalectomy increased body temperature of MSG-treated mice to normal (male mice) or almost normal (female mice). Adrenalectomy increased BAT mitochondrial guanosine 5'-diphosphate binding in MSG-treated mice, indicative of an increased thermogenic state, but had the same effect in control mice. We conclude that obesity in the MSG-treated mouse is secondary to the high level of corticosterone in its blood, which raises its metabolic efficiency, an effect of corticosterone also seen in normal lean mice, and causes it to thermoregulate at a low energy-conserving level. This latter effect is peculiar to the MSG-treated mouse and is not seen in corticosterone-treated normal mice.
Effect of dietary protein on in vivo insulin action and liver glycogen repletion
Authors: Rossetti L. , Rothman D. L. , DeFronzo R. A. , Shulman G. I.
Published: December 2017

To investigate the influence of dietary manipulation on in vivo glucose metabolism, we pair fed normal rats for 10 days with one of three diets: 1) high protein-low carbohydrate (Hi-PN) (n = 20); 2) intermediate protein (I-PN) (n = 11); and 3) low protein-high carbohydrate (Lo-PN) (n = 18). Fasting glucose, postmeal plasma glucose, and insulin concentrations were as follows: 118 +/- 2 mg/dl, 138 +/- 2 mg/dl, and 4.0 +/- 0.2 ng/ml in Hi-PN; 111 +/- 3 mg/dl, 147 +/- 3 mg/dl, and 5.1 +/- 0.3 ng/ml in I-PN; 102 +/- 2 mg/dl, 162 +/- 2 mg/dl, and 6.0 +/- 0.2 ng/ml in Lo-PN, respectively. Basic hepatic glucose production (HGP) was 6.6 +/- 0.2 in Hi-PN, 6.1 +/- 0.2 in I-PN, and 5.6 +/- 0.1 mg.kg-1.min-1 in Lo-PN. Insulin sensitivity was assessed with the euglycemic clamp using two insulin infusion rates: 2 and 4 mU.kg-1.min-1. The rate of glucose disappearance was 14.8 +/- 0.4 and 25.3 +/- 0.7 in Hi-PN, 15.3 +/- 0.4 and 26.9 +/- 0.5 in I-PN, and 16.1 +/- 0.6 and 31.5 +/- 0.5 mg.kg-1.min-1 in Lo-PN, respectively. HGP was suppressed by 86 in the 2- and by 90% in the 4-mU insulin clamp in the Lo-PN, whereas HGP was suppressed by 45 and by 79% in the two steps in the Hi-PN group.(ABSTRACT TRUNCATED AT 250 WORDS)
Neuropeptide Y in the human female genital tract: localization and biological action
Authors: Jorgensen J. C. , Sheikh S. P. , Forman A. , Norgard M. , Schwartz T. W. , Ottesen B.
Published: December 2017

The distribution, localization, and smooth muscle effects of neuropeptide Y (NPY) were studied in the human female genital tract. High concentrations of NPY immunoreactivity were demonstrated in the uterine artery, the ovary, the fallopian tube, cervix, and the vagina. The NPY immunoreactivity was confined to nerve fibers. The highest density of nerve fibers was observed in relation to blood vessels, although some NPY-immunoreactive nerves were also seen close to nonvascular smooth muscle. The NPY-immunoreactive material throughout the genital tract was identical to synthetic amidated human NPY with regard to size, hydrophobicity, and charge as evaluated by gel filtration, high-performance liquid chromatography, and isoelectric focusing. NPY (10(-10) to 10(-6) M) exerted a direct vasoconstrictory effect on small arteries dissected from the cervix and an additive effect of NPY and norepinephrine responses was observed. Exogenous NPY did not have a direct effect on nonvascular smooth muscle specimens from the fallopian tube or the myometrium. The close relation between NPY-immunoreactive nerves and blood vessels, the presence of NPY-immunoreactive material identical to amidated synthetic human NPY, and the vasoconstrictory effects of NPY indicate that NPY is involved in the regulation of the blood flow in the human female genital tract.
Possible sources of glutamine for parenteral nutrition: impact on glutamine metabolism
Authors: Abumrad N. N. , Morse E. L. , Lochs H. , Williams P. E. , Adibi S. A.
Published: December 2017

Due to its instability, glutamine is not included in solutions for parenteral solution. This problem can be obviated by providing glutamine as acetyl-, glycyl-, or alanylglutamine. Using an organ balance technique in conscious dogs, we investigated metabolism of these three sources of glutamine. Liver, gut, kidney, and muscle participated in clearance of glycyl- and alanylglutamine from plasma, but among these organs only kidney cleared acetylglutamine. Furthermore, there was a large urinary excretion for acetylglutamine (38 +/- 6% of amount infused) but only a trace amount for either dipeptide. The infusion of glutamine-dipeptides resulted in similar increases in blood level of free glutamine. The main source of this increase appeared to be hydrolysis of dipeptides by kidney and release of free glutamine to circulation. During the infusion of both dipeptides, glutamine balance (free and dipeptide forms) was always positive (net uptake) across liver, gut, and kidney but was neutral across muscle. Liver or gut glutamine balances were not significantly different during the infusion of dipeptides, but kidney glutamine balance was twofold greater during the infusion of glycyl- than alanylglutamine. We conclude that among these three sources of glutamine, acetylglutamine is least desirable for use in parenteral nutrition. Glycylglutamine may be preferable over alanylglutamine if the objective is to target glutamine for kidney.
Interaction of calcium with porcine adrenal chromogranin A (secretory protein-I) and chromogranin B (secretogranin I)
Authors: Gorr S. U. , Shioi J. , Cohn D. V.
Published: December 2017

Secretory granules of endocrine cells contain one or more of the acidic secretory proteins chromogranin A (secretory protein-I), chromogranin B (secretogranin I), and secretogranin II (chromogranin C). It has been proposed that these proteins play a role in the packaging of secretory products. In the present study, lysates of purified porcine adrenal chromaffin granules containing chromogranins A and B and a putative chromogranin B fragment bound calcium and formed aggregates in the presence of 10–20 mM calcium at pH 5–6 and at 100 mM or less KCl, NaCl, or norepinephrine. The precipitates contained virtually all of the chromogranin B and the chromogranin B fragment and about one-third of the chromogranin A. The aggregates did not form or were dissociated at the pH and salt concentration of the extracellular fluid. Calcium precipitated purified chromogranin A and chromogranin B from pure solution to the same extent as from the granule lysates. Parathormone, added to the lysates, was incorporated in the precipitates, whereas the acidic secretory protein ovalbumin and norepinephrine were not. These findings suggest that secretory protein-I and secretogranin can exist in situ as aggregates that may include selected secretory products.
Na+-K+-ATPase pump function in rat brain synaptosomes is different in males and females
Authors: Fraser C. L. , Sarnacki P.
Published: December 2017

To understand the increased morbidity and mortality associated with acute hyponatremia in young women, we characterized the Na+-K+-adenosinetriphosphtase (ATPase) pump in rat brain synaptosomes to determine if this adaptive mechanism was different between the sexes. Veratridine-stimulated sodium (Na+) uptake was significantly greater (P less than 0.001) in females than in males (8.08 +/- 0.3 vs. 5.56 +/- 0.4 nmol/mg protein), suggesting either an increased rate of Na+ uptake and/or decreased extrusion of Na+ by the Na+-K+-ATPase pump in females. Uptake rate was determined by measuring Na+ transport at 5 s, and it was found to be twice as large in females as in males (1.01 +/- 0.2 vs. 0.46 +/- 0.1 nmol/mg protein). However, in the presence of 2.5 mM ouabain, uptake in both groups were similar, suggesting that the difference was probably due to decreased function of the Na+-K+-ATPase pump in females. Transport evaluation of the Na+-K+-ATPase pump showed ouabain-sensitive K+ uptake in males to be significantly greater (P less than 0.001) than in females (10.53 vs. 4.97 nmol/mg protein), and ouabain-sensitive Na+ uptake in inverted synaptosomes was 70% greater in males (4.00 vs. 2.37 nmol/mg protein). [3H]ouabain binding studies showed maximum binding capacity in males and females to be similar (103 +/- 12 vs. 110 +/- 15 pmol/mg protein), whereas the dissociation constant was significantly (P less than 0.005) greater in males (109 +/- 8 vs. 82 +/- 6 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
Cyclic nucleotides and polyamines in prolactin stimulation of lactose biosynthesis
Authors: Oppat C. A. , Rillema J. A.
Published: December 2017

The possible roles of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) and of polyamines on the early effect of prolactin (PRL) on lactose biosynthesis have been investigated in cultured mammary gland explants derived from mice 12-14 days pregnant. Elevated cAMP concentrations impaired the PRL stimulation of [3H]glucose incorporation into lactose. Adding dibutyryl cAMP (0.1-0.5 mM) or phosphodiesterase inhibitors [methyl isobutylxanthine (0.1-0.5 mM) or theophylline (0.5-5.0 mM)] to the culture medium abolished the PRL response. The addition of 8-bromo cGMP (0.5 mM) with or without 1.0 mM spermidine had no effect on the PRL stimulation of lactose synthesis. By itself, 1.0 mM spermidine consistently produces a small but significant PRL-like stimulation of lactose synthesis in this system. Ongoing polyamine metabolism appears to be necessary for the PRL effect on lactose synthesis because 100 microM methylglyoxal bis(guanyl hydrazone), an inhibitor of S-adenosyl methionine decarboxylase, abolished the PRL response. alpha-Difluoromethylornithine, an inhibitor of ornithine decarboxylase activity, at concentrations from 1.0 to 10 mM had no effect on the PRL stimulation of lactose synthesis.
Alpha-adrenoceptors and insulin release from pancreatic islets of normal and diabetic rats
Authors: Ostenson C. G. , Cattaneo A. G. , Doxey J. C. , Efendic S.
Published: December 2017

The role of alpha-adrenoceptors in the regulation of glucose-induced insulin release (GIR) was investigated in islets of normal and neonatally streptozotocin-injected non-insulin-dependent diabetic rats (STZ). In normal islets GIR was suppressed to approximately 50% by 10(-8) M of the alpha 2-adrenergic agonist UK 14304, whereas 10(-9) M of the agonist induced a similar inhibition in STZ islets. In normal islets, suppression of GIR by UK 14304 (10(-8) M) was totally antagonized by 10(6) M idazoxan (alpha 2-antagonist) or 10(6) M phentolamine (alpha 1 + alpha 2-antagonist). In STZ islets, the inhibitory effect of UK 14304 (10(-9) M) was entirely reversed by 10(-5) M idazoxan or 10(-6) M phentolamine. The alpha 1-antagonist prazosin (10(-7)-10(-5) M) was without effect on insulin release suppressed by UK 14304 in normal and STZ islets. Insulin release at 3.3, 8.3, or 16.7 mM glucose was augmented by phentolamine but not by idazoxan. It is concluded that the inhibitory effect of catecholamines on insulin release is mediated by alpha 2-receptors in normal and STZ islets. Phentolamine augments basal and glucose-induced insulin release by a mechanism that does not involve alpha 2-adrenoceptors.
Human insulin receptor radioimmunoassay: applicability to insulin-resistant states
Authors: Pezzino V. , Papa V. , Trischitta V. , Brunetti A. , Goodman P. A. , Treutelaar M. K. , Williams J. A. , Maddux B. A. , Vigneri R. , Goldfine I. D.
Published: December 2017

A radioimmunoassay of the human insulin receptor was developed employing a potent rabbit polyclonal antibody to the human insulin receptor and a highly purified human placental insulin receptor preparation. The receptor, obtained by sequential affinity chromatography with insulin receptor monoclonal antibody-agarose and wheat germ agglutinin-agarose, was radiolabeled with 125I-Bolton-Hunter reagent at specific activities of 2,100-3,300 Ci/mmol. Over 75% of this ligand was immunoprecipitable with the polyclonal antireceptor antibody and remained immunoprecipitable for greater than 45 days. The assay was sensitive to unlabeled receptor concentrations as low as 0.2 ng/0.5 ml; unlabeled insulin did not cross-react and unlabeled insulin-like growth factor (IGF)-I receptor cross-reacted weakly. The radioimmunoassay was applicable to the measurement of insulin receptors in tissues and cells that were extracted by solubilization in 1% Triton X-100; no purification of the extracted receptor was necessary. Of the three major target tissues for insulin action studied, liver had the highest concentration of receptors (47.6 ng/mg protein); fat and muscle had lower levels. Other studies with the radioimmunoassay indicated that insulin receptors were decreased both in monocytes from obese hyperinsulinemic subjects and in fibroblasts from patients with leprechaunism.
Exercise training increases the number of glucose transporters in rat adipose cells
Authors: Hirshman M. F. , Wardzala L. J. , Goodyear L. J. , Fuller S. P. , Horton E. D. , Horton E. S.
Published: December 2017

We studied the mechanism for the increase in glucose transport activity that occurs in adipose cells of exercise-trained rats. Glucose transport activity, glucose metabolism, and the subcellular distribution of glucose transporters were measured in adipose cells from rats raised in wheel cages for 6 wk (mean total exercise 350 km/rat), age-matched sedentary controls, and young sedentary controls matched for adipose cell size. Basal rates of glucose transport and metabolism were greater in cells from exercise-trained rats compared with young controls, and insulin-stimulated rates were greater in the exercise-trained rats compared with both age-matched and young controls. The numbers of plasma membrane glucose transporters were not different among groups in the basal state; however, with insulin stimulation, cells from exercise-trained animals had significantly more plasma membrane transporters than young controls or age-matched controls. Exercise-trained rats also had more low-density microsomal transporters than control rats in the basal state. When the total number of glucose transporters/cell was calculated, the exercise-trained rats had 42% more transporters than did either control group. These studies demonstrate that the increased glucose transport and metabolism observed in insulin-stimulated adipose cells from exercise-trained rats is due, primarily, to an increase in the number of plasma membrane glucose transporters translocated from an enlarged intracellular pool.
Bone response to normal weight bearing after a period of skeletal unloading
Authors: Sessions N. D. , Halloran B. P. , Bikle D. D. , Wronski T. J. , Cone C. M. , Morey-Holton E.
Published: December 2017

Skeletal unloading in the growing rat induces a temporary inhibition of bone formation and thereby a deficit in bone calcium compared with age-matched, normally loaded animals. To determine whether this deficit can be restored by skeletal reloading we measured bone formation rate at the tibiofibular junction and total bone calcium in the tibia and lumbar vertebra in rats whose hindlimbs were unloaded for 2 wk and then reloaded by return to normal weight bearing. Continuously loaded or unloaded animals were also studied. Skeletal unloading reduced bone formation by 34% and tibial and vertebral calcium by 12 and 22%, respectively. Reloading significantly increased the rates of bone formation and calcium accretion 30-34% above normally loaded animals, and by 2 wk had decreased the deficit in tibial and vertebral calcium by 36 and 23%, respectively. These data indicate that the deficit in bone calcium induced by skeletal unloading in the growing rat can be restored in part by return to normal weight bearing. However, the time required to restore bone calcium exceeds the time required to produce the original calcium deficit.
Basolateral and apical binding, internalization, and degradation of insulin by cultured kidney epithelial cells
Authors: Rabkin R. , Yagil C. , Frank B.
Published: December 2017

In vivo, filtered insulin is absorbed and degraded in proximal tubules after binding to the apical membrane. Peritubular removal also occurs and involves basolateral receptor binding and degradation. Whether basolateral degradation proceeds within the cell or on the cell surface is unknown. Because of the difficulties in addressing this question in vivo, this study was carried out with a cultured opossum kidney epithelium cell line with proximal-like features and insulin receptors. Cells were grown in partitioned wells on polycarbonate filters and, when confluent, the monolayer effectively separated the culture well into apical and basolateral compartments. Apical and basolateral binding, internalization, and degradation were studied separately by incubating monolayers with 125I-insulin added to either the apical or basal compartment. At 37 degrees C insulin associated with either pole in a time-dependent manner. This interaction was specific, for it was competitively inhibited by cold insulin but not by unrelated peptides. Separation of surface-bound from internalized insulin was achieved by lowering extracellular pH. At 4 degrees C, 92% of the radioactivity added to either side of the monolayer was surface-bound, whereas at 37 degrees C and after 1 h, 57% was surface-bound and 43% internalized. Affinity of apical and basolateral receptors were similar (1-2 nM), but basolateral receptor number was greater, for at high insulin concentrations (5 x 10(-8) M) basolateral membrane binding exceeded apical by fivefold (250 +/- 81 vs. 56 +/- 11 fm/10(6) cells). Degradation followed exposure to either pole of the cell.(ABSTRACT TRUNCATED AT 250 WORDS)
Growth hormone effects on hepatic glutamate handling in vivo
Authors: Welbourne T. , Joshi S. , McVie R.
Published: December 2017

Growth hormone administration affects growth in hypophysectomized animals by depressing urea synthesis and redistributing nitrogen into protein. Because the liver is the site of ureagenesis and glutamine is the major interorgan nitrogen vehicle, we studied hepatic glutamine uptake in relation to urea release in hypophysectomized and growth hormone-supplemented, 100 micrograms/100 g body wt hypophysectomized rats. In vivo hepatic balances for glutamine, glutamate, alanine, and urea were performed on anesthetized animals by simultaneous measurement of flow through the liver and the respective arteriovenous and portovenous concentration differences. On the whole animal level, growth hormone-administered hypophysectomized rats exhibited restored growth and decreased urea excretion associated with a reduction in arterial urea and elevation in arterial glutamate, but glutamine and alanine concentrations were unchanged. On the organ level, growth hormone treatment reduced hepatic urea release from 3,145 +/- 432 to 1,954 +/- 320 nmol.min-1.100 g-1. However, neither glutamine uptake, 342 +/- 110 and 494 +/- 135 nmol.min-1.100 g-1 nor alanine uptake, 522 +/- 120 vs. 363 +/- 109 nmol.min-1.100 g-1 were altered by growth hormone treatment. In marked contrast, net glutamate uptake by the hypophysectomized rat liver, 71 +/- 15 nmol.min-1.100 g-1, was reversed by growth hormone administration to a striking net release rate of 960 +/- 229 nmol.min-1.100 g-1, suggesting that glutamine nitrogen is spared incorporation into urea by shunting into glutamate and release into the blood.
Measurement of non-steady-state free fatty acid turnover
Authors: Jensen M. D. , Heiling V. , Miles J. M.
Published: December 2017

The accuracy of non-steady-state equations for measuring changes in free fatty acid rate of appearance (Ra) is unknown. In the present study, endogenous lipolysis (traced with [14C]-linoleate) was pharmacologically suppressed in six conscious mongrel dogs. A computer-responsive infusion pump was then used to deliver an intravenous oleic acid emulsion in both constant and linear gradient infusion modes. Both non-steady-state equations with various effective volumes of distribution (V) and steady-state equations were used to measure oleate Ra [( 14C]oleate). Endogenous lipolysis did not change during the experiment. When oleate Ra increased in a linear gradient fashion, only non-steady-state equations with a large (150 ml/kg) V resulted in erroneous values (9% overestimate, P less than 0.05). In contrast, when oleate Ra decreased in a similar fashion, steady-state and standard non-steady-state equations (V = plasma volume = 50 ml/kg) overestimated total oleate Ra (18 and 7%, P less than 0.001 and P less than 0.05, respectively). Overall, non-steady-state equations with an effective V of 90 ml/kg (1.8 x plasma volume) allowed the most accurate estimates of oleate Ra.