Biomedical subjects

S R Bloom

Publications and source records attributed to S R Bloom.

At least 199 records · Page 11Linked to original sources

PubMed1995

Acute effects of central neuropeptide Y injection on glucose metabolism in fasted rats.

1. Neuropeptide Y is a potent appetite stimulant and has been found to modulate glucose metabolism when given chronically. The acute effects of neuropeptide on peripheral glucose handling have not been studied in detail. We have studied the acute effects of central nervous system injection of neuropeptide on glucose metabolism in vivo in the rat. 2. Rats implanted with chronic cannulae in the third cerebral ventricle were injected with either neuropeptide Y or saline and peripheral insulin sensitivity was assessed during a hyperinsulinaemic euglycaemic clamp. The effect of centrally injected neuropeptide Y on post-absorptive glucose metabolism was studied using a constant infusion of [6-3H]glucose. 3. Infusion of neuropeptide Y resulted in a 18% increase in glucose requirement during the clamp, suggesting increased peripheral tissue responsiveness to insulin. Neuropeptide Y injection in 10h fasted rats increased plasma glucose (area under curve 9.9 +/- 0.2 versus 9.1 +/- 0.1 mmol h-1l-1, P < 0.01), insulin (103 +/- 23 versus 33 +/- 8 pmol/l, P < 0.01, at 30 min) and glucagon (5.5 +/- 0.5 versus 3.1 +/- 0.3 pmol/l, P < 0.05, at 30 min). The increase in plasma glucose was due to an initial increase in the rate of appearance, which peaked between 20 and 30 min after neuropeptide Y infusion; over the entire 90 min 16% more glucose entered the systemic circulation in the neuropeptide Y-treated rats than in control rats, and the total quantity of glucose removed was also greater. 4. Neuropeptide Y in the central nervous system influences glucose metabolism by altering secretion of islet hormones, hepatic glucose production and the peripheral response to insulin.

Animals↗

PubMed1995

The role of nitric oxide in the control of protein secretion in the submandibular gland of the cat.

Submandibular salivary responses to stimulation of the parasympathetic chorda lingual innervation have been investigated in anaesthetized cats in the presence and absence of N omega-arginine-L-methyl ester (L-NAME) to block the synthesis of nitric oxide. Stimulation either at 2 Hz continuously or at 20 Hz for 1 s at 10 s intervals produced an abrupt fall in submandibular vascular resistance and initiated a flow of submandibular saliva. Neither of these responses differed significantly from the other but the output of protein was significantly potentiated (P < 0.05) when the high-frequency intermittent pattern of stimulation was employed. This potentiation of protein output was abolished in the presence of L-NAME, when the output of protein from the gland was closely similar, whichever pattern of stimulation was employed. Additional administration of atropine completely blocked all submandibular responses to parasympathetic stimulation showing that, in the presence of L-NAME, each response was due to release of acetylcholine acting on muscarinic receptors. The intermittent pattern of chorda lingual nerve stimulation produced a significant rise in the output of vasoactive intestinal peptide (VIP) from the gland (P < 0.01) and this response was significantly reduced following administration of L-NAME (P < 0.05). The results are consistent with the contention that stimulation of the parasympathetic innervation in bursts, which increases the amount of VIP released from the postganglionic nerve terminals, enhances the output of protein in submandibular saliva in the cat. The mechanism involves nitric oxide (NO), which may act, at least in part, presynaptically by modulating VIP release.

Animals↗

PubMed1995

Binding sites for islet amyloid polypeptide in mammalian lung: species variation and effects on adenylyl cyclase.

Islet amyloid polypeptide (IAPP) and calcitonin gene related peptide (CGRP) share a 47% sequence homology. IAPP can interact with adenylyl cyclase coupled CGRP receptors. We have examined [125I]IAPP binding in mouse, pig, and guinea pig lung membranes in competition with IAPP, CGRP, and CGRP(8-37). Three types of site were shown by order of potency: (i) mouse, IAPP > CGRP(8-37) >> CGRP; (ii) pig, CGRP > IAPP > CGRP(8-37); and (iii) guinea pig, CGRP = IAPP = CGRP(8-37). Chemical cross-linking of [125I]IAPP and [125I]CGRP binding sites in lung demonstrated that both sites had similar molecular weights in any one species but differed across species, i.e., mouse M(r) = 70,000 and 98,000; pig M(r) = 68,000, 56,000, and 47,000; and guinea pig M(r) = 106,000 and 56,000. Adenylyl cyclase activity was stimulated by forskolin and AlCl3-NaF in rat, mouse, pig, and guinea pig membranes. Only in mouse and pig were CGRP and IAPP able to stimulate adenylyl cyclase activity. In mouse lung CGRP and IAPP stimulated adenylyl cyclase activity with EC50 values of 642 +/- 222 nM (n = 4) and 325 +/- 115 nM (n = 4), respectively. In pig lung membranes EC50 values were 5.7 +/- nM (n = 4) for CGRP and 1230 +/- 1130 nM (n = 4) for IAPP. Thus IAPP either did not stimulate adenylyl cyclase activity in these lung membranes or did so with a low potency.

Adenylyl Cyclases↗

PubMed1995

Gastrointestinal and pancreatic hormones in the human fetus and mother at 18-21 weeks of gestation.

Several gastrointestinal hormones appear to play an important developmental role in the newborn, particularly in preterm neonates. Although the cells producing these peptides develop towards the end of the first trimester, fetal secretion of these regulatory peptides has not hitherto been demonstrated. Using samples collected by fetoscopy at 19-21 weeks of gestation we have measured concentrations of several gastrointestinal and pancreatic hormones. Maternal venous and amniotic fluid hormone concentrations were measured simultaneously. Concentrations of the pancreatic hormones, insulin, glucagon and pancreatic polypeptide (PP) were similar in fetal and maternal blood. Gastrin and motilin were present in the fetal circulation but at about 30% (p < 0.05) and 60% (p < 0.01) of the maternal levels, respectively. In contrast, enteroglucagon concentrations were more than twofold higher in the fetal circulation compared with maternal levels (p < 0.05). Concentrations of gastric inhibitory polypeptide (GIP) in fetal blood were higher than levels in maternal blood but not significantly. Concentrations of GIP (p < 0.001) were higher in the amniotic fluid than the fetal circulation. Gastrin and glucagon levels were similar in amniotic fluid and fetal blood. In contrast, PP and motilin were present in amniotic fluid, but at lower concentrations than in fetal blood. Enteroglucagon was not detectable in amniotic fluid. In conclusion, several alimentary hormones are secreted in the fetus at midterm. Since these peptides have trophic, secretory and motor effects on the gut, it is likely that these regulatory peptides are involved in the functional development of the fetal intestine.

Amniotic Fluid↗

PubMed1995

Endothelin in bronchoalveolar lavage fluid and its relation to airflow obstruction in asthma.

Endothelins (ETs) are a family of peptide mediators that have a number of biological properties, including the ability to act as potent bronchoconstrictors of isolated human airways. To examine the possible involvement of ET in asthma, we have performed fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) on 10 healthy control subjects, 10 patients with atopic asthma treated with bronchodilators alone, and 8 patients with atopic asthma treated with inhaled and/or oral corticosteroids. Endothelin concentrations in BAL fluid were measured by radioimmunoassay and total protein concentrations by a colorimetric method. There was a significant increase in the BAL fluid ET levels in the non-steroid-treated patients with asthma compared with the normal subjects, when expressed either as a concentration (median, 0.30 versus 0.08 pM; p = 0.001) or in relation to total protein (median, 3.02 versus 1.08 pmol/g; p = 0.01). There was, however, no statistically significant difference in ET levels between the steroid-treated patients with asthma, and either of the other two groups. In the non-steroid-treated patients with asthma there was a significant negative correlation between the BAL fluid ET concentration and the % predicted FEV1 (r = -0.71, p = 0.03). This correlation was not significant in the steroid-treated subjects, and no correlation between BAL fluid ET concentrations and bronchial reactivity was found in any of the three groups. These findings are consistent with the hypothesis that ET contributes to the pathophysiology of asthma.

Adrenal Cortex Hormones↗

PubMed1995

Glucagon-like peptide-1 is a physiological incretin in rat.

Glucagon-like peptide-1 7-36 amide (GLP-1) has been postulated to be the primary hormonal mediator of the entero-insular axis but evidence has been indirect. The discovery of exendin (9-39), a GLP-1 receptor antagonist, allowed this to be further investigated. The IC50 for GLP-1 receptor binding, using RIN 5AH beta-cell membranes, was found to be 0.36 nmol/l for GLP-1 and 3.44 nmol/l for exendin (9-39). There was no competition by exendin (9-39) at binding sites for glucagon or related peptides. In the anaesthetized fasted rat, insulin release after four doses of GLP-1 (0.1, 0.2, 0.3, and 0.4 nmol/kg) was tested by a 2-min intravenous infusion. Exendin (9-39) (1.5, 3.0, and 4.5 nmol/kg) was administered with GLP-1 0.3 nmol/kg, or saline, and only the highest dose fully inhibited insulin release. Exendin (9-39) at 4.5 nmol/kg had no effect on glucose, arginine, vasoactive intestinal peptide or glucose-dependent insulinotropic peptide stimulated insulin secretion. Postprandial insulin release was studied in conditioned conscious rats after a standard meal. Exendin (9-39) (0.5 nmol/kg) considerably reduced postprandial insulin concentrations, for example by 48% at 15 min (431 +/- 21 pmol/l saline, 224 +/- 32 pmol/l exendin, P < 0.001). Thus, GLP-1 appears to play a major role in the entero-insular axis.

Anesthesia↗

PubMed1995

Pyroglutamyl-phenylalanyl-proline amide attenuates thyrotropin-releasing hormone-stimulated insulin secretion in perifused rat islets and insulin-secreting clonal beta-cell lines.

TRH immunoreactivity has been detected in the pancreas of man and rat and localized to the islets of Langerhans. We studied the effect of synthetic TRH and the related tripeptide pyroglutamyl-phenylalanyl-proline amide (EFP) on isolated perifused rat islets and the glucose-responsive clonal cell lines HIT-T15 and RIN5AH. TRH at 10 nM potentiated [0.5 +/- 0.1 (control) vs. 0.8 +/- 0.1 (TRH) pmol/10(6) cells per 120 min; mean +/- SEM; n = 6; P < 0.001; n = 15], whereas EFP from 1 nM upwards suppressed glucose-stimulated insulin secretion [0.8 +/- 0.1 (control) vs. 0.5 +/- 0.1 (EFP) pmol/10(6) cells per 120 min; P < 0.001; n = 12) in the cell lines. Further, EFP reversed TRH-stimulated insulin release. Similar responses were observed in perifused isolated rat islets at the tested dose of 1 microM. Gel permeation chromatography of rat adult and neonatal whole pancreas, isolated islets, and HIT cell extracts demonstrated the elution of total TRH-like immunoreactivity (t-TRH-LI) in the same position as synthetic TRH. Cation exchange analysis of the t-TRH-LI from rat adult pancreas and HIT cell extracts showed that neutral TRH-like peptides corresponding to synthetic EFP were also present. Reverse-phase fast protein liquid chromatographic analysis of t-TRH-LI in the unbound fraction of these extracts subjected to anion exchange columns, also demonstrated peaks corresponding to synthetic EFP. We conclude that TRH potentiates, whereas EFP inhibits, glucose-stimulated insulin release in isolated perifused islets and the cell lines. In addition, EFP reversed the stimulatory effect of TRH. The presence of EFP-LI in rat adult and neonatal pancreas and HIT cell extracts suggests it may contribute in the modulation of pancreatic endocrine function.

Amino Acid Sequence↗

PubMed1995

Cloning and molecular characterization of complementary deoxyribonucleic acid corresponding to a novel form of pituitary adenylate cyclase-activating polypeptide messenger ribonucleic acid in the rat testis.

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide that greatly stimulates adenylyl cyclase activity in cultured anterior pituitary cells, was isolated from ovine hypothalamus in 1989. Investigation of the distribution of PACAP messenger RNA (mRNA) in rat tissues by Northern blot analysis revealed an anomalous signal in the testis. In this study we have isolated and characterized this unusual mRNA, which is approximately 800 bases long (approximately 1.5 kilobases shorter than that reported in the rat hypothalamus). Cloning and sequencing of the complementary DNA corresponding to this message revealed that the sequences are identical except for 126 bases at the 5'-end of the 5'-untranslated region of the smaller transcript. This region has no homology to either the published hypothalamic sequence or any other known sequence. Northern blot analysis of total RNA from various species showed that a smaller form of PACAP mRNA is also present in human, murine, and bovine testis, although in these species the message is slightly smaller. In addition, Northern blot analysis of these tissues using a probe directed to the 126-base 5'-region, revealed conservation of this sequence between species. Although the structure of the rat PACAP gene is unknown, preliminary investigations into the origins of the two mRNA species by PCR of genomic DNA suggests that they are transcribed from separate genes and not the product of alternate splicing.

Amino Acid Sequence↗

PubMed1995

Gonadal steroids regulate rat anterior pituitary levels of TSH-releasing hormone- and pyroglutamyl-glutamyl-proline amide-like immunoreactivity.

The novel peptide, pyroglutamylglutamylprolineamide (pGlu-Glu-ProNH2, EEP), which has structural and immunological similarities to TRH (pGlu-His-ProNH2) has recently been shown to contribute to total TRH-like immunoreactivity (t-TRH-LI) detected in the rabbit prostate and rat and porcine anterior pituitary. This study was undertaken to determine the effects of gonadal steroids on t-TRH-LI and its components in the rat hypothalamus and pituitary. EEP-like immunoreactivity (EEP-LI) was separated from TRH-LI by ion exchange chromatography and detected by TRH RIA. Although male and female posterior pituitary and hypothalamic t-TRH-LI levels were similar, the mean t-TRH-LI in female anterior pituitaries was significantly lower than that in males, 10.3 +/- 2.9 pmol/g vs. 24.4 +/- 2.5 pmol/g (P < 0.01). Anion exchange analysis of control anterior pituitary samples distinguished two peaks of t-TRH-LI, corresponding to [125I]-TRH marker and [3H]-EEP markers. In control female anterior pituitaries EEP-LI accounted for 26.0 +/- 2.4% of t-TRH-LI, whereas in males it accounted for 43.3 +/- 5.3% of the total. Hypothalamic and posterior pituitary samples only contained t-TRH-LI corresponding to [125I]-TRH markers. There was no significant change in hypothalamic and posterior pituitary levels of t-TRH-LI after ovariectomy or orchidectomy. Anterior pituitary levels of t-TRH-LI, however, were increased by an estimated 6-fold after ovariectomy and 2-fold after orchidectomy. After ovariectomy, the proportions of t-TRH-LI accounted for by TRH-LI and EEP-LI were reversed in the female. EEP-LI now accounted for the majority of t-TRH-LI, constituting an increase of approximately 21-fold in pituitary EEP-LI levels. The changes in the levels of pituitary TRH-LI and EEP-LI induced by ovariectomy were reversed by 17-beta-estradiol. As in the ovariectomized samples EEP-LI was increased (2-fold) by orchidectomy. Both TRH-LI, which increased 1.6-fold, and EEP-LI were restored to control values after testosterone replacement. These findings confirm the hypothesis that pituitary TRH-LI and EEP-LI are regulated by gonadal status. The fact that these changes were not observed in the hypothalamus and posterior pituitary suggests that TRH-LI and EEP-LI have specific functional significance in the pituitary gland.

Animals↗

PubMed1995

An abundant and specific binding site for the novel vasodilator adrenomedullin in the rat.

Rat adrenomedullin is a novel 50-amino acid peptide with structural similarities to the calcitonin family of peptides, calcitonin, calcitonin gene-related peptide (CGRP), and islet amyloid polypeptide (IAPP). Using rat [125I]adrenomedullin, specific binding sites were demonstrated in heart, lung, spleen, liver, soleus, diaphragm, gastrocnemius, and spinal cord membranes. The highest binding was present in heart and lung, which was further characterized. These sites exhibited saturation, dissociation, and competition. In rat lung, only rat (IC50 = 5.8 nM) and human (IC50 = 94 nM) adrenomedullin competed with [125I]adrenomedullin. However, in rat heart, rat (IC50 = 0.2 nM) and human (IC50 = 4.2 nM) adrenomedullin, IAPP (IC50 = 240 nM), and CGRP (IC50 = 1050 nM) all competed with [125I] adrenomedullin. Saturation analysis revealed binding capacities and dissociation constants of 2.8 +/- 0.3 pmol/mg protein and 1.3 +/- 0.3 nM, respectively, in lung and 0.47 +/- 0.11 pmol/mg protein and 0.41 +/- 0.14 nM in heart. Comparison with [125I]CGRP- and [125I]IAPP-binding sites in lung showed that rat adrenomedullin could potently inhibit at these sites (IC50 = 5 and 6 nM, respectively). Chemical cross-linking demonstrated a major band of 83,000 mol wt in lung, diaphragm, spleen, and liver and a band of 94,000 mol wt in heart, soleus, and gastrocnemius. Thus, [125I]adrenomedullin-binding sites in rat lung are abundant and can be differentiated from binding sites in rat heart, both pharmacologically and by mol wt.

Adrenomedullin↗

PubMed1995

Expression of a novel receptor for the calcitonin peptide family and a salmon calcitonin-like peptide in the alpha-thyrotropin thyrotroph cell line.

We have previously shown an increased incidence of alpha-subunit-producing thyrotroph tumors after salmon calcitonin (sCT) injection into rats. However, it is not clear whether the effects of CT are direct or indirect. Our hypothesis was that for sCT to act directly, it must have a binding site on thyrotrophs. The alpha TSH cell line was used as a model for thyrotrophs. Receptor binding studies using alpha TSH membranes revealed a high affinity binding site for sCT [IC50 = 0.97 +/- 0.18 nM (n = 4); Kd = 5.45 +/- 0.43 nM (n = 3); binding capacity = 6.6 pmol/mg protein (n = 3)]. Rat CT did not compete with binding at this site. Receptor screening for other CT peptide family members revealed high specific binding for CT gene-related peptide (CGRP; IC50 = 0.25 +/- 0.08 nM; n = 3) and islet amyloid polypeptide (IC50 = 4.36 +/- 1.1 nM; n = 3). This together with the absence of rat CT binding excluded a conventional CT-binding site, and we propose a site similar to the CGRP subtype III receptor described in the rat nucleus accumbens. Guanosine 5'O-(3-thiotriphosphate) (GTP gamma S) (20 microM), reduced [125I]CGRP binding to 38% of maximal, indicating that this site is G-protein coupled. Immunocytochemically, all of the cells displayed intense sCT-like immunoreactivity, which was totally abolished by preabsorption of the antibody with sCT. The presence of this receptor supports the hypothesis that sCT mediates tumorigenesis via a direct pituitary action and, together with the coexistence of a sCT-like peptide in these cells, provides evidence for a possible autocrine role of this peptide in the control of thyrotroph function.

Amyloid↗

PubMed1995

Cloning and characterization of the cDNA encoding the human neuromedin U (NmU) precursor: NmU expression in the human gastrointestinal tract.

Many peptide precursors encode more than one bioactive peptide. Recent cloning of the rat neuromedin U (NmU) precursor revealed potential proteolytic processing sites which may generate three associated peptides in addition to the NmU peptide, which is known to have potent uterine contractile effects. To assess the degree of evolutionary conservation, which often suggests conserved biological function and hence physiological importance, we have cloned and sequenced the cDNA encoding the human NmU precursor. Sequence analysis revealed a 174 amino acid human precursor containing the 25 residue NmU peptide near the C terminus of the precursor. The human message sequence was 74% homologous with that of the rat, indicating evolutionary conservation of the precursor between these two species. Four out of five of the putative proteolytic processing sites, first revealed in the rat precursor, were conserved in the human precursor, indicating a similar processing mechanism in both species. Two such processing sites flank a 33 residue peptide sequence which differed in only two amino acids compared with the rat homologue. This conservation suggests a possible biological role for this putative peptide. Northern blot analysis of human gastrointestinal tissues revealed a similar level of mRNA throughout the gastrointestinal tract. RIA using a porcine specific assay showed the highest levels of peptide in the jejunum samples.

Amino Acid Sequence↗

PubMed1995

In vivo and in vitro effects of dexamethasone on pituitary thyrotrophin-releasing hormone-like peptide concentrations in the rat.

The novel peptide, pyroglutamyl-glutamyl-proline amide (pGlu-Glu-ProNH2; EEP), which has structural and immunological similarities to TRH (pGlu-His-ProNH2) has recently been shown to contribute to total TRH-like immunoreactivity (t-TRH-LI) detected in the rabbit prostate and rat and porcine anterior pituitary. In this study, the effects of dexamethasone (DEX) on rat pituitary TRH-like peptide levels in the rat were determined. TRH-like immunoreactivity (TRH-LI) was separated by ion exchange chromatography and detected by TRH RIA. Anion exchange chromatographic analysis suggested that EEP-like immunoreactivity (EEP-LI) accounted for 15.0 +/- 1.2 pmol t-TRH-LI/g (70.4 +/- 3.9%) in the control anterior pituitary with the remaining t-TRH-LI being due to TRH-LI. Following DEX treatment pituitary EEP-LI and TRH-LI increased by 200% and 400% (P < 0.001) respectively, constituting a 2.5-fold increase in t-TRH-LI in the pituitary. TRH-LI now accounted for 45.7 +/- 5.3% of t-TRH-LI compared with 29.6 +/- 4.1% in the controls. TRH-LI, but not EEP-LI, was detected in the hypothalamus and posterior pituitary, suggesting that EEP-LI is synthesised within the anterior pituitary. DEX also caused a 2.6-fold rise (P < 0.001) in t-TRH-LI in dispersed, cultured anterior pituitary cells. Chromatographic analysis of cultured pituitary cell extracts revealed that the majority of t-TRH-LI (> 98%) was due to TRH-LI.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

A 67 kDa protein mediates pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide-stimulated insulin secretion in a hamster clonal beta-cell line.

Insulin secretion is regulated by neural and neurohormonal factors. The report of nerves releasing pituitary adenylate cyclase-activating polypeptide (PACAP)--a 38 amino acid peptide--in the endocrine pancreas, suggests it may be important in modulating insulin release. We therefore carried out receptor-binding studies on membranes prepared from the glucose-responsive clonal beta-cell line HIT-T15, and also examined the effects of PACAP38, PACAP27--a C-terminal truncated form of the peptide--and vasoactive intestinal peptide (VIP) on insulin and islet amyloid polypeptide (IAPP) release. We showed by chemical cross-linking that PACAP and VIP stimulate secretion from the clonal cells by binding to a receptor with a molecular weight of 67 kDa (n = 4). Binding was saturable when membranes were incubated with 125I-PACAP27 (Kd 1.2 +/- 0.2 nM; Bmax 415.7 +/- 35.3 fmol/mg; n = 4) or 125I-VIP (Kd 1.3 +/- 0.3 nM; Bmax 354.8 +/- 42.8 fmol/mg; n = 4). We also demonstrated an increase in glucose-stimulated insulin (PACAP27, 366.6 +/- 25.8%; PACAP38, 389.9 +/- 13.4%; VIP, 342.6 +/- 16.1% of control; all at 1 microM, P < 0.01 vs control) and IAPP release (PACAP27, 236.9 +/- 26.2%; PACAP38, 226.5 +/- 10.9%; VIP, 242.9 +/- 15.8% of control; all at 1 microM, P < 0.01 vs control). Incubation of the cells with these peptides, for a duration of 12 h, in the presence of 5.5 mM glucose, did not alter the expression of insulin or IAPP. These findings suggest that PACAP and VIP stimulate secretion of insulin and IAPP by binding to a 67 kDa protein on clonal beta-cells and do not alter the transcription of insulin and IAPP under the conditions tested.

Amyloid↗

PubMed1995

Insulin secretion and plasma levels of glucose-dependent insulinotropic peptide and glucagon-like peptide 1 [7-36 amide] after oral glucose in cirrhosis.

A blunted initial insulin secretory response may contribute to oral glucose intolerance in cirrhosis. Oral glucose is a better stimulant to insulin secretion than intravenous (IV) glucose in part because of release of gut peptides, notably glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 [7-36 amide] (GLP-1 [7-36 amide]). Because impaired release of or resistance to these gut peptides could explain impaired insulin secretion after oral glucose, we measured insulin secretion, plasma GIP, and GLP-1 [7-36 amide] levels, basally and after 75 g oral glucose, in 10 cirrhotics and 10 controls. Insulin secretion was calculated from a two-compartment analysis of serum C-peptide levels using kinetic parameters derived from IV injection of recombinant human C-peptide. C-peptide metabolic clearance rate, and the fractional rate constants for C-peptide (using the two-compartment model) were not significantly different, but the volume of the central compartment was 15% greater in cirrhotics (P < .01). Fasting blood glucose levels were similar (cirrhotics, 4.9 +/- 0.2; controls, 4.6 +/- 0.1 mmol/L) but serum insulin was six times higher in cirrhotics (P < .001). Cirrhotics had higher fasting GIP (215 +/- 72 vs. 42 +/- 18 pmol/L) and GLP-1 [7-36 amide] levels (25 +/- 3 vs. 16 +/- 1 pmol/L) (both P < .05). After oral glucose, blood glucose levels were significantly higher in cirrhotics. The timing of the gut peptide response to oral glucose was similar in the two groups, but peak levels of both peptides were approximately x2 higher in the cirrhotics.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Effect of food deprivation and streptozotocin-induced diabetes on hypothalamic neuropeptide Y release as measured by a radioimmunoassay-linked microdialysis procedure.

Central administration of neuropeptide Y (NPY) produces a robust feeding response in the rat. It is still unclear how, and in response to what endogenous stimuli NPY is released. We have developed a radioimmunoassay-linked microdialysis procedure for measuring hypothalamic NPY release in both the anaesthetised and freely moving rat. We have used the procedure to show that anaesthesia dramatically decreased NPY release, while a 48 h period of food deprivation significantly increased extracellular NPY concentrations. Streptozotocin-induced diabetic rats also showed increased hypothalamic NPY release compared to controls. These results provide more evidence that NPY may be involved in mediating the hyperphagia associated with starvation and diabetes mellitus. The development of a sensitive microdialysis procedure to measure NPY will allow further detailed investigation of the hypothalamic NPY system.

Anesthesia↗

PubMed1994

The presence of islet amyloid polypeptide/calcitonin gene-related peptide/salmon calcitonin binding sites in the rat nucleus accumbens.

Receptor autoradiographic analysis of binding in rat brain sections for [125I]islet amyloid polypeptide (IAPP), [125I]calcitonin gene-related peptide (CGRP) and [125I]salmon calcitonin indicated dense binding for all three ligands in the nucleus accumbens. Membrane binding studies revealed the existence of high affinity sites for all three peptides. The order of potency of various related peptides at each binding site was investigated and found for [125I]IAPP to be salmon calcitonin > IAPP = alpha CGRP > salmon calcitonin-(8-32); for [125I]CGRP to be alpha CGRP > IAPP > salmon calcitonin; and for [125I]salmon calcitonin to be salmon calcitonin > alpha CGRP > rat calcitonin > salmon calcitonin-(8-32) > IAPP, suggesting that [125I]IAPP targets the CGRP3 receptor subtype. This study confirms the existence of two receptors in the rat nucleus accumbens binding salmon calcitonin, one of which binds alpha CGRP and IAPP with a high affinity.

Amyloid↗

PubMed1994

Nitric oxide-related pancreatic endocrine responses to hyperglycaemia in the conscious calf.

Mean plasma insulin concentration was reduced and mean plasma glucose concentration increased following the administration of N-nitro-L-arginine methyl ester (L-NAME; 100 mumol kg-1 i.a.) in conscious calves given continuous infusions of exogenous glucose (30-60 mumol min-1 kg-1 i.v.). It is concluded that the rise in plasma insulin concentration which occurs in these animals in response to glucose is mediated, at least in part, by a nitric oxide-related factor (NOx).

Animals↗