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

After preparative high-performance liquid chromatography of mouse islet culture medium, concentrated on disposable C18 cartridges (Sep-Pak), an unexpected insulin immunoreactive peak eluting earlier than mouse insulin I and II was detected. Molecular mass determination by mass spectrometry supported its suspected identity as methionine sulphoxide insulin II. We have examined the formation of Met-O derivatives of insulin II, glucagon and pancreatic polypeptide during sample preparation (Sep-Pak and Speed-Vac concentrating). The oxidation of methionine residues was found to depend very much on the buffer, the organic modifier and the procedure. In particular the use of methanol-trifluoroacetic acid resulted in extensive oxidation. The oxidation could be minimized by adding 2 mM dithiothreitol to the buffer and by degassing and/or nitrogen-bubbling of the buffer. Minimal formation of Met-O derivatives is important for the quantitation of methionine-containing polypeptides.
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PMID:High-performance liquid chromatography of rat and mouse islet polypeptides: potential risk of oxidation of methionine residues during sample preparation. 227 17

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.
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PMID:Effect of specific amino acid groups on renal hemodynamics in humans. 233 Sep 90

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.
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PMID:Peptidergic modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre. 243 97

The control of RNA degradation by amino acids, insulin, and glucagon was investigated in perfused livers of fed rats previously labeled in vivo with [6-14C] orotic acid; rates were determined from the release of [14C]cytidine in the presence of 0.5 mM cytidine to suppress reutilization. Studies with cyclically perfused livers showed that plasma amino acids at 10 times (10X) normal concentrations inhibited RNA breakdown by 85%. Similar inhibition was obtained with a known regulatory amino acid mixture (Leu, Met, Pro, Trp, and His), whereas leucine alone (0.8 mM) decreased degradation by 47%. Perfusions carried out in the single-pass mode with graded levels of plasma amino acids revealed that the acceleration of RNA degradation over the full range of amino acid deprivation (0 to 10X normal levels) was the same as that for protein breakdown (3.19 and 3.15% h-1, respectively), and both were equally suppressed by insulin (2.4 micrograms h-1). Glucagon (10 micrograms h-1), though, was far less effective in stimulating RNA than protein turnover. A direct comparison of the two dose responses revealed a strong dissociation at 1 and 2 times normal amino acid levels. These findings support the notion that RNA and protein are degraded within a single macroautophagic compartment during amino acid and insulin deprivation. Glucagon, however, appeared to induce a second pathway in which the proportion of sequestered RNA to protein was selectively reduced. Electron micrographs showed that the ratio of vacuoles containing rough as compared with smooth endoplasmic reticulum was decreased by nearly 80% under these conditions.
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PMID:Amino acid and hormonal control of macromolecular turnover in perfused rat liver. Evidence for selective autophagy. 244 87

Developmental patterns for rat pancreatic opioid peptides and islet hormones were studied from gestational day 20 through adulthood. Fetal tissue was obtained as well as pancreas at birth (day 0), and postnatal days 3, 7, 14, and 21, and 7 weeks. The hormones measured included insulin, glucagon, and somatostatin. The opioids measured were beta-endorphin, Met- and Leu-enkephalins, and the high molecular weight enkephalin precursors. Pancreata were pooled as necessary and extracted (acid alcohol, or hot acetic acid), and opioids were further purified on reversed-phase C-18 (Sep-pak) cartridges. In all instances measurements were made by radioimmunoassays. Precursor peptides were first digested (with trypsin and carboxypeptidase B) prior to immunoassay. All opioids and hormones except the precursors for enkephalins showed a well-defined surge in pancreatic concentration during the first postnatal week. In contrast, the precursors had the highest concentration in the fetus, and by the seventh day of life had decreased by greater than 50%. This progressive decrease may represent maturation of the enkephalin convertase and trypsin-like enzymes in the islets. The opioid and hormonal surges that we have described are similar to the surge in islet concentration of thyroid-releasing hormone (TRH) previously described in neonatal rat islets. It is suggested that these postnatal alterations in opioid and hormone concentration relate to a specific function in the development of the endocrine pancreas.
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PMID:Developmental patterns for pancreatic opioids in the rat. 253 May 76

The degradation of intracellular protein and other cytoplasmic macromolecules in liver is an ongoing process that regulates cytoplasmic mass and provides amino acids for energy and other metabolic uses early in starvation. Cellular proteins are conveniently divided into two general classes according to readily discernable differences in average rates of turnover. A short-lived class, having a half-life of approximately 10 min, comprises about 0.6% of total protein. Its degradation is not physiologically controlled, and the mechanism is probably nonlysosomal in nature. The second or long-lived group, with an average half-life 250 times greater, constitutes more than 99% of the cell's protein. By contrast, its breakdown is strongly regulated, and the site of catabolism is believed to be the vacuolar-lysosomal system. Cytoplasmic sequestration by lysosomes can be divided into two categories; macro- and microautophagy. The first is induced by amino acid and/or insulin deprivation. Amino acids are considered to be primary regulators, since they can control this process over the full range of induced proteolysis in the absence of hormones. Glucagon, cyclic AMP, and beta-agonists also stimulate macroautophagy in hepatocytes but have opposite effects in myocytes. Micrautophagy differs from the former in that the cytoplasmic "bite" is smaller and the uptake process is not acutely regulated. However, the latter does decrease during starvation in parallel with basal proteolysis, effects that might be linked to the loss of endoplasmic reticulum. The primary control of macroautophagy is accomplished through a small group of direct regulators (Leu, Tyr/Phe, Gln, Pro, Met, His, and Trp) and a specific coregulatory action of alanine. As a group, regulatory amino acids produce direct inhibitory responses in the perfused rat liver that are identical to those of the complete amino acid mixture at 0.5x and 4x (times) normal plasma concentrations. However, they lose effectiveness almost completely within a narrow zone centered at normal levels, a loss that can be abolished by the addition of alanine at its normal plasma concentration (0.5 mM). At this level, alanine does not inhibit directly. Interestingly, this zonal loss is also eliminated by insulin. Glucagon, though, specifically blocks the initial inhibition evoked by 0.5x amino acid mixtures and thus induces maximal rates of protein degradation at normal amino acid concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Mechanism and regulation of protein degradation in liver. 264 36

COOH-terminal decapeptide of gastrin-releasing peptide (GRP-10) is a bombesin-like peptide, which has bioactivities to stimulate gastrin, insulin, and glucagon secretion. We have synthesized an analogue of GRP-10 that inhibits GRP-10's stimulation of insulin secretion both in vivo and in vitro and glucagon secretion in vivo, while potentiating the stimulation of gastrin secretion. The amino acid sequence of this peptide is H-Gly-Asn-Trp-Ala-Ala-Gly-His-Leu-Met-NH2 ([Ala6]GRP-10). Because the stimulation of insulin and gastrin secretion by GRP-10 has been ascribed to a direct effect on B- and G-cells, these findings suggest that there are two subtypes of receptors for bombesin-like peptides in mammalian tissues.
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PMID:[Ala6]gastrin-releasing peptide-10: an analogue with dissociated biological activities. 266 16

The biologic activities of three synthetic analogues of CCK-4 (Trp-Met-Asp-Phe-NH2) in which (i) the C-terminal residue Phe was N-methylated (peptide I); (ii) the C-terminal Phe residue was N-methylated and Ser is substituted for Met in position 2 (peptide II); (iii) Pro was substituted for Trp in position 1 and the C-terminal amino nitrogen was methylated (peptide III), have been described. Peptides I and II have been found to inhibit the release of both insulin and glucagon, while peptide III was found to be a potent releasing agent for insulin and an inhibitor for glucagon.
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PMID:Effect of some novel synthetic analogues of CCK-4 on insulin and glucagon secretion. 269 15

Five antisera against insulin (Ins), glucagon (Glu), somatostatin (SRIF), met-enkephalin (met-enk), and serotonin (5-HT) were used for immunofluorescence detection of endocrine cells in pancreas and gastrointestinal tract (GIT) of the European eel (Anguilla anguilla L.) at three stages of development (leptocephalic larva, glass-eel, and adult eel). Comparable distribution of endocrine cells was observed for adults and glass-eels. In their pancreatic islets, positive immunoreactions were obtained only for Ins, SRIF, and Glu; this later was also present in the pancreatic ducts. 5-HT cells were present throughout the GIT. SRIF cells were situated mostly in the stomach and less in the intestine. Met-enk cells were abundant in the pyloric cecum, but less frequent in the intestinal mucosa. Glu cells were present only in the intestine. No insulin-immunoreactive cells could be detected in the GIT. The pancreatic islets of leptocephalic larvae exhibited a strong reaction for SRIF, a weak reaction for Glu, and none at all for Ins, met-Enk, or 5-HT. The GIT of these larvae contained numerous met-enk cells, mainly in the foregut. In the fore- and midgut, cells exhibited a weak fluorescence after treatment with Glu antiserum. No positive immunoreactive cells were observed with 5-HT, SRIF, or Ins antisera.
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PMID:Detection of endocrine cells by immunofluorescence method in the gastroenteropancreatic system of the adult eel, glass-eel, and leptocephalic larva (Anguilla anguilla L.). 286 Nov 42

The anglerfish endocrine pancreas expresses two different genes for preproglucagon. The regions of the two proglucagons that correspond to glucagon have different sequences, as do the two glucagon-like peptides (GLPs). The products derived from processing the more abundant proglucagon-II have recently been determined. However, it was not known whether proglucagon-I was processed to similar products. The two major biologically active products of preproglucagon-I processing (glucagon-I and GLP-I) have now been purified to homogeneity. Their structures were determined using automated gas phase Edman degradation, tryptic mapping, and fast atom bombardment mass spectrometry. The preproglucagon-I-processing sites were identified. Glucagon-I represents residues 53-81, and GLP-I corresponds to preproglucagon-I-(91-124) (numbering from the initiator Met).
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PMID:Pancreatic proglucagon processing: isolation and structures of glucagon and glucagon-like peptide from gene I. 305 56


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