Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific 125I-labelled vasoactive intestinal peptide (VIP) binding was determined in feline renal cortical and medullary plasma membranes. For the cortex, Scatchard analysis of the data resulted in a curvilinear plot with a high-affinity site K0.5 of 8.4 +/- 2.6 nmol l-1 (SE, n = 6) and a second low-affinity site K0.5 204 +/- 16 nmol l-1 with binding site concentrations (Bmax) of 385 +/- 44.5 and 2710 +/- 181.3 fmol mg protein-1 respectively. Conversely a similar analysis of the results obtained for outer medullary membranes gave a single site with a K0.5 of 1.2 +/- 0.2 nmol l-1 (SE, n = 4) and Bmax of 157.8 +/- 24.7 fmol mg-1. Inner medullary membrane binding data. Gave a single site of lower affinity (K0.5 = 62.5 +/- 21.6 nmol l-1; n = 3). Structurally related peptides, glucagon and secretin, were ineffective (up to 1 mumol l-1) in displacing VIP from specific sites in both cortex and medulla. Porcine PHI 1-27 (a peptide having N-terminal histidine and C-terminal isoleucine) and a VIP antagonist [4-Cl-D-Phe6Leu17]VIP both displaced 125I-VIP from cortical and medullary membrane binding sites with IC50 values of 43.0 nmol l-1 and 1.3 mumol l-1 (cortex) and 132.0 nmol l-1 and 1.5 mumol l-1 (medulla) respectively. The localisation of specific VIP binding sites in feline kidney was investigated further by in vitro autoradiography.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Localisation and characterisation of functional vasoactive intestinal peptide receptors in feline kidney. 216 36

The vasoactive intestinal peptide (VIP) receptors were identified on the membranes from the rat anterior pituitary gland with [125I]VIP. The dissociation constant (Kd) and the maximal binding capacity (Bmax) values were estimated from the competitive inhibition data. The Kd and Bmax values were 1.05 +/- 0.75 nM and 103 +/- 11 fmol/mg protein, respectively. The order of molar potency of related peptides to inhibit [125I]VIP binding was VIP greater than peptide histidine isoleucine (PHI) greater than secretin greater than glucagon. Glucagon was not effective to inhibit the binding. [125I]VIP binding was effectively inhibited by the addition of guanine nucleotides. The order of molar potency to inhibit the binding was Gpp(NH)p greater than GTP greater than GDP greater than GMP greater than ATP. These results directly suggest the coupling of VIP receptors with guanine nucleotide binding proteins in the anterior pituitary gland.
 ...
PMID:Direct demonstration of guanine nucleotide sensitive receptors for vasoactive intestinal peptide in the anterior lobe of the rat pituitary gland. 216 81

Fasting concentrations, clearance of exogenous infused amino acids, and lean body mass were studied in a patient with glucagonoma syndrome (fasting glucagon = 380 pmol/l, normal range 15-45 pmol). The fasting concentrations of all amino acids were reduced. The clearances of alanine, arginine, glycine, isoleucine, leucine, lysine, methionine, proline, serine, threonine, and tyrosine were increased. The urea synthesis rate during amino acid infusion was 27 mumols/kg per minute (normal range 20-24 mumols/kg per minute). The lean body mass of the patients was reduced to 59% of the expected value. It is suggested that the weight loss of patients with glucagonoma syndrome is partly due to increased hepatic conversion of amino acid nitrogen to urea nitrogen, resulting in decreased blood amino acid concentration, and secondary to this, organ protein catabolism, as shown by the decreased lean body mass.
 ...
PMID:Increased amino acid clearance and urea synthesis in a patient with glucagonoma. 216 78

Despite its name, Vasoactive Intestinal Peptide (VIP), a 28-amino acid peptide, is widely distributed in the eye where it is thought to play a physiological role, particularly in aqueous humor dynamics or retinal neurotransmission. Localization and pharmacological properties of VIP binding sites were investigated in eyes from albino rabbit and rat using an in vitro autoradiographic method. 125I-VIP was used as ligand and unlabelled VIP was used to displace labelled VIP. Autoradiograms were generated by apposing the slides to 3H-Ultrofilm or autoradiographic emulsion and analysed using an image analysis system. Specific binding represented about 85% of total binding. Kinetic studies showed that equilibrium was reached after 140 min incubation at room temperature. Biochemical investigations demonstrated that 125I-VIP bound to a population of sites with high affinity (Kd = 2.95 +/- 0.5 nM). Inhibition of 125I-VIP binding with VIP and related peptide gave a rank order of potency: VIP greater than peptide histidine isoleucine greater than secretin greater than human growth hormone-releasing factor, glucagon, VIP1-14, VIP14-28. In both species, specific binding were found in conjunctiva, iris, ciliary processes, choroid and retina. Quantitative analysis of autoradiograms revealed that the highest densities of binding sites were localized in the ciliary epithelium in rabbits and in the inner retina in rats.
 ...
PMID:[Autoradiographic localization and characterization of the ocular binding sites of the VIP (vasoactive intestinal peptide) in albino rats and rabbits]. 217 30

The effect of specific amino acid groups on renal hemodynamics was examined in seven healthy young volunteers. Each subject received a 3-h intravenous infusion according to one of the following protocols: study 1, gluconeogenic amino acids (Arg, Gly, Pro, Cys, Met, Ser); study 2, alanine alone; study 3, branched-chain amino acids (BCAA, Leu, Ile, Val); or study 4, 0.9% saline. The rise (40-60% above base line) in total plasma amino acid concentration was similar in studies 1-3; no change was observed in study 4. During study 1, glomerular filtration rate (GFR) rose by 16% (from 98 +/- 6 to 114 +/- 8 ml.1.73 m-2.min-1, P less than 0.01), and renal plasma flow (RPF) rose by 28% (from 496 +/- 47 to 638 +/- 70 ml.1.73 m-2.min-1, P less than 0.01). After alanine (study 2) and BCAA (study 3) infusion, there was a slight, although not significant, rise in GFR and RPF; during saline infusion (study 4), GFR and RPF remained unchanged. Plasma insulin and growth hormone did not change significantly in any study protocol. Plasma glucagon rose significantly by 30% in study 1 (from 117 +/- 10 to 151 +/- 13 pg/ml, P less than 0.05) but did not change in studies 2-4. In summary, infusion of mixed gluconeogenic amino acids increases both GFR and RPF, and neither alanine nor BCAA infusion caused a consistent alteration in renal hemodynamics.
 ...
PMID:Effect of specific amino acid groups on renal hemodynamics in humans. 233 Sep 90

The ileocaecal junctions of 5 horses and 2 donkeys were examined by using antisera to the following peptides: somatostatin, glucagon, gastrin, neurotensin, vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), calcitonin gene-related peptide (CGRP), substance P (SP) and neuropeptide Y (NPY). Antisera to somatostatin, neurotensin and NPY demonstrated endocrine cells in the ileal- and caecal parts of the ileocaecal junction, while immunoreactivity for glucagon was demonstrated in endocrine cells of the ileal part only. Nerve cell bodies showing immunoreactivity to SP, VIP, CGRP and PHI were demonstrated in the myenteric and submucosal plexuses and were associated with small blood vessels in the submucosa of all the regions tested. Ramified nerve fibres in the submucosa immunoreactive to SP, VIP, CGRP and PHI extended to the mucosa and to small blood vessels in the submucosa. Nerve fibres showing immunoreactivity to SP, VIP and PHI extended to the circular smooth muscle layer of the ileocaecal junction.
 ...
PMID:An immunohistochemical study of various peptide-containing endocrine cells and neurones at the equine ileocaecal junction. 233 94

The effects of a range of neuropeptides were investigated on the membrane potential of the Schwann cells of the giant nerve fibre of the tropical squid. Vasoactive intestinal peptide (VIP) produced a dose-dependent, long-lasting hyperpolarization of the Schwann-cell membrane potential. Among peptides structurally related to VIP, similar effects were produced by peptide histidine isoleucine (PHI) but not by secretin and glucagon. Substance P and somatostatin also hyperpolarized the Schwann-cell membrane potential but via receptor systems distinct from those activated by VIP. Methionine enkephalin ([Met]-enkephalin) blocked the actions of all the above peptides as well as the effects of DL-octopamine and carbachol. The actions of [Met]-enkephalin upon the VIP responses were antagonized by naloxone. VIP produces its effects on the Schwann-cell membrane potential via a receptor system that is independent from those described previously which mediate the effects of carbachol and DL-octopamine. However, VIP can potentiate the effects of the latter systems. The actions of VIP on the Schwann cell are unlikely to be mediated via changes in adenosine 3',5'-cyclic monophosphate (cyclic AMP) levels and are insensitive to changes in the level of extracellular calcium in the superfusate. The actions of VIP are, however, potentiated in the presence of low concentrations of lithium ions suggesting that the VIP receptor may mediate its effects by inducing the hydrolysis of polyphosphatidylinositols in the Schwann-cell membrane. Evidence is presented for the existence of an endogenous VIP-like component in the normal hyperpolarizing action of giant-axon activity on the membrane potential of the Schwann cell.
 ...
PMID:Peptidergic modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre. 243 97

Vasoactive intestinal polypeptide (VIP) has been shown to stimulate melatonin synthesis in mammalian pineal; however, a regulatory role for VIP in the avian pineal has not been explored. Immunocytochemical and physiological response experiments were performed to investigate whether 1) immunoreactive VIP fibers innervated the avian pineal gland; 2) VIP had a specific effect on melatonin release that was mediated by cAMP stimulation; and 3) alpha 2-adrenergic signal transduction was associated with a reduction in cAMP levels. Immunocytochemical experiments demonstrated the presence of both tyrosine hydroxylase- and VIP-immunoreactive fibers in the avian pineal gland. Treatment of dispersed chick pineal cell cultures with VIP stimulated melatonin release (maximum 6-fold increase; EC50 = 1.8 nM) when administered during the 12-h light period of a 12-h light, 12-h dark cycle. Of the other four peptides tested [porcine VIP-(10-28), porcine peptide histidine isoleucine, porcine secretin, and human glucagon), only peptide histidine isoleucine stimulated melatonin release (EC50 = 30 nM). The effect of VIP was mediated by a time- and dose-dependent increase in cAMP accumulation (maximum 4-fold increase). The specific alpha 2-agonist UK-14,304 reduced cAMP accumulation (maximum 43% reduction) and inhibited melatonin release (EC50 = 19 nM) in the presence of 3 X 10(-8) M VIP. Norepinephrine-induced inhibition of nocturnal melatonin release was blocked by the elevation of cAMP achieved through the administration of forskolin (EC50 = 0.2 microM), isobutylmethylxanthine (EC50 = 112 microM), or 8-bromo-cAMP (EC50 = 166 microM). Collectively, these results demonstrate the presence and functional significance of VIP in the avian pineal gland, and the interaction of VIP and norepinephrine at the level of cAMP in the regulation of melatonin biosynthesis.
 ...
PMID:Vasoactive intestinal polypeptide and alpha 2-adrenoceptor agonists regulate adenosine 3',5'-monophosphate accumulation and melatonin release in chick pineal cell cultures. 247 31

The hydroxylation of tyrosine to dopa is the rate-limiting reaction in catecholamine biosynthesis. It has been previously reported that secretin, vasoactive intestinal peptide and peptide histidine isoleucine amide, all members of the secretin-glucagon family of peptides, increase dopa synthesis in superior cervical ganglia in vitro. We report here that two other members of this peptide family, rat growth hormone-releasing factor and helodermin H38, a component of Gila monster venom, also increase the rate of dopa synthesis, while glucagon-like peptides I and II and a number of other peptides tested produce no effect. Since analogs of cAMP also increase dopa synthesis, it is of particular interest that all of the peptides that increase catechol synthesis also raise the levels of this cyclic nucleotide in the superior cervical ganglion. Helodermin H38 stimulated the rate of dopa synthesis and the level of cAMP with similar potencies (EC50S of approximately 10 nM) and with maximal effects of two- and two-fold, respectively. By either measure, rat growth hormone-releasing factor produced a two-fold increase at 10 microM and a three- to four-fold increase at 30 microM. Analogs of peptides of the secretin-glucagon family with a deletion or modification of the N-terminal histidine were much less effective in these assays at the concentrations tested than were their parent compounds, demonstrating an important role for this amino acid in conferring activity on these peptides. In addition to increasing dopa synthesis in intact tissue, incubation of ganglia with rat growth hormone-releasing factor, secretin, vasoactive intestinal peptide or peptide histidine isoleucine amide also increased the activity of tyrosine hydroxylase measured subsequently in ganglion homogenates. Thus, the peptidergic stimulation of dopa synthesis observed in the intact superior cervical ganglion appears to be due, at least in part, to the activation of tyrosine hydroxylase. Together with previous studies, these findings support the hypothesis that certain members of the secretin-glucagon family increase catecholamine synthesis in sympathetic neurons by a cAMP-dependent activation of tyrosine hydroxylase.
 ...
PMID:Activation of ganglionic tyrosine hydroxylase by peptides of the secretin-glucagon family: structure-function studies. 257 Mar 76

Vasoactive intestinal peptide (VIP) is a candidate as an inhibitory neurotransmitter mediating relaxation of the lower esophageal sphincter (LES) because VIP antiserum reduces LES relaxation in response to neural stimulation. Vasoactive intestinal peptide antiserum, however, does not completely block LES relaxation. Thus it is possible that other neurotransmitters may be involved. Peptide histidine isoleucine has structural homologies with VIP, is synthesized with VIP from a common precursor protein, coexists in some nerve cells, and is coproduced with VIP in some tumors. In numerous organ systems VIP and peptide histidine isoleucine (PHI) produce similar effects, with PHI being less potent than VIP by approximately one log number. In the LES both VIP and PHI produce tetrodotoxin-resistant dose-dependent relaxation, with PHI being almost equipotent with VIP. We therefore tested the hypothesis that PHI may be a second neurotransmitter, partly responsible for relaxation of the cat LES, by using a highly specific rabbit PHI antiserum that exhibits minimal cross-binding with VIP, secretin, and glucagon. In 3 animals, LES and brain tissue were extracted in 0.1 N HCl and assayed with a PHI radioimmunoassay. The antiserum cross-reacted with cat brain and LES showing PHI concentrations greater than 100 ng/g, with the LES containing equal or greater concentrations of PHI than brain tissue. In other animals consecutive LES circular muscle strips were cut, mounted in 1-ml muscle chambers, and stimulated with 6-s square-wave trains of 0.1-, 0.2-, 0.4-, and 0.8-ms pulses at 1, 2, and 5 Hz. These parameters produced relaxation that was completely blocked by tetrodotoxin, and reduced by VIP antiserum, but not affected by adrenergic or cholinergic receptor antagonists. Some strips were incubated in 5% or 10% PHI antiserum, whereas others were incubated in the same concentration of preimmunization serum from the same animal. Incubation in normal serum did not significantly affect relaxation, whereas in the antiserum-treated strips, LES relaxation was reduced by a significant amount (20%-30%) at all parameters of stimulation tested. Incubation in antiserum however had no effect on relaxation induced by VIP (10(-8)-10(-6) M). These data suggest that PHI may play a role in LES relaxation induced by electrical stimulation.
 ...
PMID:Role of peptide histidine isoleucine in relaxation of cat lower esophageal sphincter. 257 42


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>