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)

The effects on the conceptus of persistently decreased maternal plasma amino acid concentrations were studied in pregnant rats by the infusion of glucagon (0.21 mg/day) to the mother from day 14 to 20 of gestation with a subcutaneous, osmotically driven minipump. Controls received diluent. The experimental animals either had normal caloric intake and weight gain, or diminished caloric intake with no weight gain. Both experimental groups exhibited a decrease in plasma total amino acid concentration of approximately 50%. Maternal plasma glucose and insulin concentrations were unaffected except for slight decreases in the low weight gain group. At cesarean section on day 20, fetal weight was unaffected in the normal weight gain group, while the low weight gain animals exhibited intrauterine growth retardation. Fetal plasma glucose and insulin concentrations were unaffected. Despite the marked decrease in maternal plasma total amino acid concentration, fetal plasma total amino acid concentration was unaffected. Individual plasma amino acid concentrations in the normal weight gain mothers and fetuses revealed a spectrum of changes. Some maternal amino acids were decreased by more than 60% (alpha-aminobutyric acid, asparagine, threonine, glutamine, alanine) while others were unaffected (tyrosine, tryptophan, phenylalanine, histidine). In general, amino acids that were decreased in the mother exhibited no change or a lesser decrease in fetal plasma concentration, while those that were unaffected in the mothers showed increased fetal concentrations. Fetuses from the low weight gain mothers had plasma amino acid profiles that were similar to those of the normal weight gain mothers.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Preserved fetal plasma amino acid concentrations in the presence of maternal hypoaminoacidemia. 379

To compare the contributions of splanchnic and skeletal muscle tissues to the disposal of intravenously administered amino acids, regional amino acid exchange was measured across the splanchnic bed and leg in 11 normal volunteers. Postabsorptively, net release of amino acids by leg (largely alanine and glutamine) was complemented by the net splanchnic uptake of amino acids. Amino acid infusion via peripheral vein (0.2 g X kg-1 X h-1) caused a doubling of plasma insulin and glucagon levels and a threefold rise in blood amino acid concentrations. Both splanchnic and leg tissues showed significant uptake of infused amino acids. Splanchnic tissues accounted for approximately 70% of the total body amino acid nitrogen disposal; splanchnic uptake was greatest for the glucogenic amino acids but also included significant quantities of branched-chain amino acids. In contrast, leg amino acid uptake was dominated by the branched-chain amino acids. Based on the measured leg balance, body skeletal muscle was estimated to remove approximately 25-30% of the total infused amino acid load and approximately 65-70% of the infused branched-chain amino acids. Amino acid infusion significantly stimulated both the leg efflux and the splanchnic uptake of glutamine (not contained in the infusate). We conclude that when amino acids are infused peripherally in normal humans, splanchnic viscera (liver and gut) are the major sites of amino acid disposal.
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PMID:Removal of infused amino acids by splanchnic and leg tissues in humans. 396 81

The mechanisms involved in the inhibitory effects of antilipolytic agents on rat liver peroxisomal fatty acid oxidative activity have been explored. Treatment of fasting rats with antilipolytic drugs (either 3,5-dimethylpyrazole (12 mg/kg body weight) or Acipimox (25 mg/kg body weight] resulted in a decrease in free fatty acid and glucose plasma levels within 5-10 and in a significant increase in the plasma glucagon to insulin ratio within 15. Changes in the fatty acid oxidative activity appeared with a 2.5-3 h delay and were then very rapid (a 30-40% decrease in the activity occurred in additional 2 h). Many peroxisomal enzyme activities (including non-beta-oxidative activities such as uricase and D-amino acid oxidase) exhibited similar changes with the same delay. Simultaneously with the enzyme changes, at the electron microscope level many autophagic vacuoles were detected in the liver cells, often containing peroxisomal structures. Glutamine, an inhibitor of proteolysis in vivo, prevented the decrease in enzyme activities. It was concluded that the decrease in peroxisomal enzyme activities may be the consequence of enhanced peroxisome degradation due to the stimulation of autophagic processes in liver cells.
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PMID:Effects of antilipolytic agents on rat liver peroxisomes and peroxisomal oxidative activities. 397 24

Glucagon has been isolated from the pancreas of Torpedo marmorata, an elasmobranchian cartilaginous fish, and purified to homogeneity using only reverse-phase high-performance liquid chromatography. Amino acid sequence analysis indicates that the molecule differs from mammalian glucagon at position 3 (glutamic acid for glutamine), position 16 (asparagine for serine), and position 20 (lysine for glutamine). Extracts of T. marmorata intestine and brain were associated with glucagon-like immunoreactivity determined by radioimmunoassay using antisera directed against the C-terminal and N-terminal to central regions of porcine glucagon. Although elasmobranchian and teleostean fish are believed to have diverged from the main line of vertebrate evolution at about the same time, the structure of two glucagons from the teleost, Lophius americanus (anglerfish) differ from mammalian glucagon by seven and nine residues. This study supports the assertion that the structure of glucagon has been highly conserved during evolution and suggests that the considerable morphological development of the pancreas is teleosts was associated with an accelerated rate of molecular evolution.
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PMID:Primary structure of glucagon from an elasmobranchian fish. Torpedo marmorata. 407 59

The effect of 20 L-amino acids upon pancreatic glucagon secretion has been studied in conscious dogs. Each amino acid was administered intravenously over a 15 min period in a dose of 1 mmole/kg of body weight to a group of four or five dogs. Pancreatic glucagon and insulin were measured by radioimmunoassay. 17 of the 20 amino acids caused a substantial increase in plasma glucagon. Asparagine had the most glucagon-stimulating activity (GSA), followed by glycine, phenylalanine, serine, aspartate, cysteine, tryptophan, alanine, glutamate, threonine, glutamine, arginine, ornithine, proline, methionine, lysine, and histidine. Only valine, leucine, and isoleucine failed to stimulate glucagon secretion, and isoleucine may have reduced it. No relationship between glucagon-stimulating activity and insulin-stimulating activity was observed. The amino acids which enter the gluconeogenic pathway as pyruvate and, which are believed to provide most of the amino acid-derived glucose, had a significantly greater GSA than the amino acids which enter as succinyl CoA or as alpha-ketoglutarate. However, pyruvate itself did not stimulate glucagon secretion. The R-chain structure of the amino acid did not appear to be related to its GSA, except that the aliphatic branched chain amino acids, valine, leucine, and isoleucine, were devoid of GSA.
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PMID:Glucagon-stimulating activity of 20 amino acids in dogs. 463 19

The metabolic response to the first fast experienced by all mammals has been studied in the newborn rat. Levels of fuels and hormones have been compared in the fetal and maternal circulations at term. Then, after cesarean section just before the normal time of birth, sequential changes in the same parameters were quantified during the first 16 h of the neonatal period. No caloric intake was permitted, and the newborns were maintained at 37 degrees C. Activities of three key hepatic enzymes involved in glucose production were estimated. Marked differences in maternal and fetal hormones and fuels were observed. Lower levels of glucose, free fatty acids, and glycerol but higher levels of lactate, alpha-amino nitrogen, alanine, and glutamine were present in the fetus. Pyruvate, glutamate, and ketone bodies were not significantly different. The combination of a strikingly higher fetal immunoreactive insulin and a slightly lower immunoreactive glucagon (pancreatic) resulted in a profound elevation in the insulin-to-glucagon ratio, a finding consistent with an organism in an anabolic state. The rat at birth presents a body composition with respect to fuels available for mobilization and conversion which is dominated by carbohydrate and protein, since little fat is present. However, at birth a transient period of hypoglycemia occurred, associated with a rapid fall in insulin and rise in glucagon, causing reversal of the insulin-to-glucagon relationship toward ratios such as were observed in the mother. After a lag period, hepatic activities of phosphorylase, glucose-6-phosphatase, and phosphoenolpyruvate carboxykinase increased. Concurrent with these enzyme changes, the blood glucose returned to levels at or above those of the fetus. Interestingly, the fall observed in levels of the gluconeogenic precursors, lactate and amino acids, preceded the rise in enzyme activities and restoration of blood glucose. After 4 h, however, hypoglycemia recurred, during a period of decreasing hepatic glycogen content and blood lactate, pyruvate, and glycerol levels but of stable or increasing amino acid concentrations. Hepatic gluconeogenesis in this phase of depleted glycogen stores was insufficient to maintain euglycemia. Substrates derived from fat showed early changes of smaller magnitude. The rise in free fatty acids which occurred was less than twofold the value at birth, though this rise persisted up to 6 h. Whereas glycerol rose transiently, acetoacetate did not change and beta-hydroxybutyrate concentration fell. Both ketone bodies showed a marked rise at 16 h. at a time of diminished free fatty acid levels. Plasma growth hormone, though higher in the fetal than the maternal circulation, showed no consistent change during the period of observation. The changes in levels of the endocrine pancreatic hormones at birth were appropriate in time, magnitude, and direction to be implicated as prime regulators of the metabolic response during the neonatal period in the rat.
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PMID:Fuels, hormones, and liver metabolism at term and during the early postnatal period in the rat. 475 Apr 49

A new procedure for the photochemical labeling of peptides and for the production of cleavable cross-links between protein molecules is given. This method is mediated through the catalytic action of the enzyme guinea pig liver transglutaminase. Each of the labeling and cross-linking reagents described here is an amine substrate for transglutaminases and, because of the narrow specificity of these enzymes, is introduced covalently only at the gamma-carboxamide group of available peptide-bound glutamine residues. Cross-linking results either solely through the action of the enzyme in the case of a diamine substrate, or by subsequent photolysis in the case of photosensitive amine substrates. Cleavable bonds in several of the substrates are disulfide or vicinal hydroxyl groups. The validity of the procedure is demonstrated by the preparation of photosensitive derivatives of substance P and glucagon 1-6 and in the cleavable covalent cross-linking of guanidinated beta-casein.
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PMID:Transglutaminase amine substrates for photochemical labeling and cleavable cross-linking of proteins. 610 32

1. Glutaminase and glutamine synthetase are simultaneously active in the intact liver, resulting in an energy consuming cycling of glutamine at a rate up to 0.2 mumol per g per min. 2. An increase in portal glutamine concentration was followed by an increased flux through glutaminase, but flux through glutamine synthetase remained unchanged. Glutaminase flux was also increased by ammonium ions or glucagon; these effects were additive. 3. Glutamine synthetase flux was increased by ammonium ions, but this activation was partly overcome by increasing portal glutamine concentrations. Glutamine synthetase flux was slightly increased by glucagon at portal glutamine concentrations of about 0.2-0.3 mM, but was strongly inhibited above 0.6 mMs. 4. During experimental metabolic acidosis there was an increased net release of glutamine by the liver, being due to opposing changes of flux through glutaminase and glutamine synthetase. Conversely, an increased glutamine uptake by the liver during metabolic alkalosis was observed due to an inhibition of glutamine synthetase and an activation of glutaminase. However, the two enzyme activities respond differently depending on whether glucagon or ammonium ions are present.
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PMID:Regulation of flux through glutaminase and glutamine synthetase in isolated perfused rat liver. 613 95

The effects of glucagon deficiency and excess on plasma concentrations of 21 amino acids were studied in six normal human subjects for 8 h. During glucagon deficiency, produced by intravenous infusion of somatostatin (0.5 mg/h) and insulin (5 mU/kg per h), amino acid concentration (sum of 21 amino acids) rose from 2,607 +/- 76 to 2,922 +/- 133 microM after 4 h (P less than 0.025). The largest increases occurred in lysine (+26%), glycine (+24%), alanine (+23%), and arginine (+23%) concentrations. During glucagon excess produced by intravenous infusion of somatostatin (0.5 mg/h), insulin (5 mU/kg per h), and glucagon (60 ng/kg per h), amino acid concentration decreased from 2,774 +/- 166 to 2,388 +/- 102 microM at 8 h (P less than 0.01). The largest decreases occurred in citrulline (-37%), proline (-32%), ornithine (-30%), tyrosine (-23%), glycine (-20%), threonine (-21%), and alanine (18%) concentrations. Urinary urea nitrogen and total nitrogen excretions were lower during glucagon deficiency than during glucagon excess (3.1 +/- 0.2 vs. 6.3 +/- 2.3 g/8 h, P less than 0.05 and 4.8 +/- 1.0 vs 7.0 +/- 2.6 g/8 h, respectively, P less than 0.05). Biostator-controlled euglycemic glucagon deficiency was produced in four normal subjects for 4 h to eliminate possible effects of changes in glucose concentration on amino acids. Amino acid concentration (sum of 18 amino acids) increases occurred in arginine (+42%), alanine (+28%), glutamine (+25%), and glycine (+16%) concentrations. The data show that small changes (-66 pg/ml and +50 pg/ml) in basal glucagon concentrations cause plasma amino acid concentrations to change in opposite directions. The finding that urinary excretion of nitrogen and urea nitrogen was greater during glucagon excess than during glucagon deficiency suggested alterations in the rate of gluconeogenesis from amino acids as one mechanism by which glucagon controls blood amino acid levels.
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PMID:Effects of glucagon on plasma amino acids. 614 2

Glucagon injected into rats caused an increase in liver N-acetylglutamate content, and coincidentally the glutamate content decreased. The liver glutamine content decreased only after 10 min, consistent with an activation of glutaminase after a lag. These observations indicate that the increased N-acetylglutamate content was not due to an increase in glutamate content caused by an activation of glutaminase (EC 3.5.1.2).
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PMID:Effects of glucagon in vivo on the N-acetylglutamate, glutamate and glutamine contents of rat liver. 614 51


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