Biomedical subjects

M A Ghatei

Publications and source records attributed to M A Ghatei.

At least 127 records · Page 7Linked to original sources

PubMed1996

Gastrointestinal hormones in short bowel syndrome. Peptide YY may be the 'colonic brake' to gastric emptying.

BACKGROUND: Short bowel patients with a jejunostomy have large volume stomal outputs, which may in part be due to rapid gastric emptying of liquid. Short bowel patients with a preserved colon do not have such a high stool output and gastric emptying of liquid is normal. AIMS: To determine if differences in the gastric emptying rate between short bowel patients with and without a colon can be related to gastrointestinal hormone changes after a meal. SUBJECTS: Seven short bowel patients with no remaining colon (jejunal length 30-160 cm) and six with jejunum in continuity with a colon (jejunal length 25-75 cm), and 12 normal subjects. METHODS: The subjects all consumed a 640 kcal meal; blood samples were taken for 180 minutes for measurement of gastrointestinal hormones. RESULTS: Patients with a colon had high fasting peptide YY values (median 71 pmol/l with a colon; 11 pmol/l normal subjects, p < 0.005) with a normal postprandial rise, but those without a colon had a low fasting (median 7 pmol/l, p = 0.076) and a reduced postprandial peptide YY response (p < 0.050). Motilin values were high in some patients without a colon. In both patient groups fasting and postprandial gastrin and cholecystokinin values were high while neurotensin values were low. There were no differences between patient groups and normal subjects in enteroglucagon, pancreatic polypeptide, or somatostatin values. CONCLUSIONS: Low peptide YY values in short bowel patients without a colon may cause rapid gastric emptying of liquid. High values of peptide YY in short bowel patients with a retained colon may slow gastric emptying of liquid and contribute to the "colonic brake'.

Adult↗

PubMed1996

Adrenomedullin activity in chronically hypoxic rat lungs.

Adrenomedullin (AM) is a novel vasodilator with structural similarities to calcitonin gene-related peptide (CGRP). This study investigated AM activity in the rat lung during hypoxia-induced pulmonary hypertension. Both rat AM (0.2-10 nmol) and alpha-CGRP (0.2-2 nmol) produced dose-related reductions in pulmonary artery pressure in the isolated perfused lung ventilated with 2% O2. Pretreatment with alpha-CGRP, which demonstrated tachyphylaxis, or its antagonist, CGRP-(8-37), reduced the hypotensive response to AM, suggesting that part of the response to AM is mediated by CGRP receptors. 125I-labeled AM and 125I-labeled CGRP binding was significantly increased in lung membranes from 7-day hypoxic animals (AM from 1.94 +/- 0.3 to 3.36 +/- 0.4 and CGRP from 0.06 +/- 0.01 to 0.12 +/- 0.02 pmol/mg protein), with no change in dissociation constant. Moreover, the hypotensive response to both peptides was increased in the lungs of 7-day hypoxic rats. There was no significant change in lung immunoreactive AM concentrations (hypoxic 5.04 +/- 0.48 vs. control 6.28 +/- 0.76 pmol/g wet wt of tissue) or steady-state AM mRNA levels in 7-day hypoxic rats. Nonetheless, AM may be useful for the acute pharmacological manipulation of pulmonary artery pressure in hypoxia-induced pulmonary hypertension.

Adrenomedullin↗

PubMed1996

Comparison of the effects of transforming growth factor alpha and epidermal growth factor on gastrointestinal proliferation and hormone release.

Epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) bind to a common receptor and are both present in the normal gastrointestinal tract. Although many studies have examined their function in isolation, there is little information directly comparing their actions. We examined the relative potency of TGF alpha and EGF in stimulating 3H-thymidine uptake into primary rat hepatocytes at various doses in vitro and on the crypt cell production rate (CCPR) within the gastrointestinal tract when infused intravenously at 49 nmol/kg/day into rats receiving total parenteral nutrition. In vitro, maximal stimulatory activity was similar in EGF- and TGF alpha-treated cells, however, the dose of EGF required to stimulate 3H-thymidine uptake to 50% of maximal levels was only one third of that required using TGF alpha. In vivo, EGF and TGF alpha significantly increased the weight and proliferative indices throughout the gastrointestinal tract. The response (as determined by CCPR) was about 80% higher in animals which had received EGF when compared to animals receiving TGF alpha. Treatment with EGF also caused significant rises in plasma PYY, enteroglucagon and gastrin levels, whereas the equivalent dose of TGF alpha only caused a significant rise in plasma gastrin levels. We conclude that TGF-alpha, like EGF, is trophic to the entire gastrointestinal tract of the rat, however, it is a less effective mitogen, and has differential hormonal effects.

Animals↗

PubMed1996

Glucagon-like peptide-1 (GLP-1) releases thyrotropin (TSH): characterization of binding sites for GLP-1 on alpha-TSH cells.

We have demonstrated specific binding sites for [125I]glucagon-like peptide 1 (GLP-1) on membranes from the rodent thyrotrope cell line, alpha-TSH. Specific [125I]GLP-1 binding was saturable and time dependent. Equilibrium saturation binding analysis was consistent with the presence of a single class of binding site (binding capacity, 85 +/- 7 fmol/mg protein) with a dissociation constant (Kd) of 28 +/- 13 pM. The specific GLP-1 receptor agonists, exendin-4 and exendin-3, and the antagonist, exendin-(9-39), bound to the receptor sites with high affinity (Ki = 190 +/- 70 pM; 130 +/- 50 and 1200 +/- 470 pM, respectively). Chemical cross-linking of [125I]GLP-1-receptor complexes revealed a single band of 64,300 +/- 100 Mr in alpha-TSH membranes. In addition, specific PCR studies demonstrated the presence of GLP-1 receptor messenger RNA. Binding of the peptide to alpha-TSH cell membranes resulted in increased intracellular cAMP concentrations (10 nM GLP-1, 1010 +/- 83 pmol/10(6) cells.h; control, 175 +/- 60 pmol/10(6) cells.h; P < 0.002), indicating that the receptor is linked to stimulation of adenylyl cyclase. GLP-1-mediated increases in cAMP were inhibited by exendin-(9-39) in a dose-dependent manner. Furthermore, GLP-1 stimulates basal TSH release from dispersed anterior pituitary cells in a concentration-dependent manner (100 nM GLP-1, 63 +/- 3 fmol/10(6) cells.h; control, 35 +/- 1 fmol/10(6) cells.h; P < 0.0005), but had no effect on basal PRL, GH, or LH release.

Animals↗

PubMed1996

Adrenomedullin inhibits feeding in the rat by a mechanism involving calcitonin gene-related peptide receptors.

The central effect of adrenomedullin on feeding was investigated in fasted rats. After intracerebroventricular administration, adrenomedullin decreased 2-h food intake in a dose-dependent manner. A dose of 1.7 nmol adrenomedullin decreased 2-h food intake by 57%. Adrenomedullin shares sequence homology with calcitonin gene-related peptide (CGRP), a central anorectic agent, and binding sites for both are present in the hypothalamus. Adrenomedullin competed for [125I]adrenomedullin- and [125I]CGRP-binding sites in hypothalamic membranes. The Kd for the [125I]adrenomedullin-binding site was 0.54 +/- 0.07 nM, with a binding capacity of 214 +/- 27 fmol/mg membrane protein (n = 3). CGRP and the CGRP receptor antagonist CGRP-(8-37) at concentrations up to 1 microM did not compete at these sites. The Kd for the CGRP-binding site was 0.10 +/- 0.02 nM, with a binding capacity of 250 +/- 31 fmol/mg, and the Ki values for adrenomedullin and CGRP-(8-37) were 4.6 +/- 2.1 and 4.0 +/- 1.6 nM, respectively (n = 3). Thus, adrenomedullin showed high affinity binding at both adrenomedullin- and CGRP-binding sites. To establish whether adrenomedullin reduces feeding via CGRP receptors, we coadministered adrenomedullin (1.7 nmol) and CGRP-(8-37) (30 nmol). The reduction in 2-h food intake induced by adrenomedullin was 50% inhibited by CGRP-(8-37). These results show that adrenomedullin decreases food intake in the rat, and this effect is mediated at least in part via CGRP receptors.

Adrenomedullin↗

PubMed1996

Presence of neuropeptide Y and its messenger ribonucleic acid in human islets: evidence for a possible paracrine role.

Neuropeptide Y (NPY) has been shown to decrease insulin secretion from rodent islets. NPY messenger ribonucleic acid (mRNA) has been demonstrated in rat and mouse pancreatic islets. We, therefore, examined human islets for the presence of NPY-encoding mRNA and NPY-like immunoreactivity. Human pancreatic islets were obtained from cadaveric organ donors, using collagenase digestion and purification on BSA density gradients. Northern blot analysis, employing a human NPY riboprobe, revealed specific NPY-encoding mRNA in the islet. Compared to the islet, NPY message abundance was 9-fold higher in the caudate nucleus and 2.4-fold higher in the temporal lobe, but it was 75% lower in the adrenal gland. NPY-like immunoreactivity was present at 2.4 +/- 0.3 fmol/microgram protein in acid-ethanol extracts from the islets. On fast protein liquid chromatography with a reverse phase column, the majority of NPY-like immunoreactivity eluted as a peak with a retention time identical to that of porcine NPY standard. Added NPY (100 nmol/L) decreased (P = 0.001) glucose-stimulated (8 mmol/L) insulin release from the human islets by 45% in a perfusion system. Therefore, human islets synthesize substantial amounts of NPY, which could act as an intra-islet paracrine regulator.

Adolescent↗

PubMed1996

Investigation of the effects of antisense oligodeoxynucleotides to islet amyloid polypeptide mRNA on insulin release, content and expression.

We have investigated the effects of antisense oligodeoxynucleotides (oligos) to islet amyloid polypeptide (IAPP) mRNA on the expression and secretion of IAPP and insulin, in the clonal beta-cell line HIT-T15. Phosphorothioate-modified oligos were cytotoxic compared with phosphodiester (D)-oligos. Of the nine oligos tested using a lipofection reagent, O3, a 30-mer D-oligo complementary to a sequence downstream of the IAPP initiation codon, showed a significant dose-dependent suppression of IAPP mRNA, with a 42% decrease at 7.5 microM, compared with a scrambled (MSO3) control oligo (n = 3, P < 0.01). A subsequent 89% suppression of IAPP release was observed in the 4-h period following antisense treatment (1.78 +/- 0.13 (MSO3) vs 0.19 +/- 0.14 (O3) pmol/10(6) cells per 240 min, n = 7, P < 0.01). A significant increase in insulin mRNA (100 +/- 10% (MSO3) vs 124 +/- 8% (O3), n = 3, P < 0.05) and insulin content (13.0 +/- 0.9 (MSO3) vs 17.4 +/- 1.4 (O3) pmol/10(6) cells, n = 7, P = 0.028) was observed following treatment with O3 at 7.5 microM. O8, a 20-mer D-oligo directed to a region of IAPP mRNA further downstream than O3, also showed a decrease in IAPP mRNA and peptide release and an increase in insulin content. No significant changes were observed in the expression and release of the unrelated beta-cell peptide, neuropeptide Y. We thus show a suppression of synthesis and release of IAPP in HIT-T15 cells using antisense oligos. The associated increase in insulin mRNA and content in these cells after treatment with IAPP antisense oligos is in accord with an inhibitor action of IAPP on insulin availability.

Amyloid↗

PubMed1996

Effects of fasting, refeeding, and intraluminal triglyceride on proglucagon expression in jejunum and ileum.

Intestinal proglucagon is thought to be synthesized primarily by the distal gut, although the role of proglucagon-derived glucagon-like peptide I (GLP-I) as a major physiological incretin would seem to be associated with production in proximal small bowel. To better characterize the sites of production of proglucagon and GLP-I in the small intestine and evaluate nutrient regulation of small bowel proglucagon and derived peptides, we evaluated the effects of fasting for 72 h and subsequent refeeding or jejunal infusion of long-chain triglyceride (LCT) for 24 h on local expression of proglucagon in proximal and distal small bowel. Proglucagon mRNA abundance and cellular localization were determined and correlated with wet weight of bowel. In jejunum, proglucagon mRNA abundance decreased by 40% with fasting (P < 0.005) and increased with refeeding to levels similar to those of ad libitum-fed animals. In ileum, fasting resulted in a 20% decrease in proglucagon mRNA (P < 0.005); in contrast to jejunum, refeeding did not result in a significant rise in ileal proglucagon mRNA abundance from fasting values. In jejunum, signal intensity of proglucagon mRNA per cell, determined by in situ hybridization, decreased with fasting (P < 0.05) and increased with refeeding (P < 0.005) in proportion to changes in mRNA abundance. Plasma enteroglucagon and GLP-I levels correlated with jejunal proglucagon mRNA. Intrajejunal infusion of LCT increased expression of proglucagon to a greater extent in jejunum than in ileum. In conclusion, enteral nutrient intake stimulates small bowel proglucagon expression; this effect is greater in jejunum than ileum, consistent with greater intraluminal nutrient exposure and the role of jejunum as a source of the major incretin GLP-I.

Animals↗

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

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

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

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↗