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)

Incorporation of 3H-uridine by RNA in Tetrahymena was differently influenced by insulin, glucagon, follicle-stimulating hormone (FSH), thyrotropic hormone (TSH), adrenocorticotropic hormone (ACTH) and chorion-gonadotropic hormone (PMSG). TSH caused it to increase considerably and durably after an initial depression, while glucagon caused it to rise over the control throughout. Insulin, and especially PMSG, depressed the incorporation of label considerably, the latter to 3-6% of the control value by 120 min. ACTH and FSH accounted for an initial depression of RNA synthesis which, however, returned to normal 30 min after treatment. Remarkably, while the chemically similar hormones acted differently, insulin and glucagon showed the same trend of positive and negative influence, respectively.
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PMID:Effect of polypeptide hormones (insulin, thyrotropin, gonadotropin, adrenocorticotropin) on RNA synthesis in Tetrahymena, as assessed from incorporation of 3H-uridine. 618 2

Rats fed ad libitum were given insulin alone (4 U/kg), glucagon alone (25 micrograms/kg), or insulin and glucagon sequentially. Phosphorylase a and synthase R activities, hepatic glycogen, uridine diphosphoglucose, inorganic phosphate (Pi), and plasma glucose, lactate, glucagon, and insulin concentrations were determined over the subsequent 40 min. In separate animals, muscle extraction of 2-deoxy-D-[3H]glucose also was determined. After glucagon administration, glycogen phosphorylase a and plasma glucose were increased within 5 min. However, the glycogen concentration did not decrease for 20 min. Glucagon administration to rats pretreated with insulin stimulated a similar increase in phosphorylase a activity. Again, glycogen was not degraded for 20 min. After insulin only, glycogen concentration remained unchanged. Plasma glucose decreased as expected. In each group, muscle extraction of 2-deoxy-D-[3H]glucose increased compared with the controls (P < 0.05). In summary, glucagon and/or insulin administration did not stimulate significant glycogen degradation for 20 min, even though phosphorylase was activated. The mechanism remains to be determined.
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PMID:Effects of glucagon with or without insulin administration on liver glycogen metabolism. 914 96

In a previous study, administration of casein hydrolysate to food-deprived rats at a dose of 4 g/kg body wt resulted in an increase in portal plasma glucagon concentration. This was associated with an activation of phosphorylase a and a decrease in hepatic glycogen concentration. The present study was undertaken to determine whether similar results would be obtained with smaller doses. Doses of 1 and 2 g/kg body wt were administered to food-deprived rats. At a dose of 2 g/kg, portal plasma glucagon concentration was significantly elevated. This was associated with a slight increase in phosphorylase a activity (P < 0.05) and a 50% decrease in hepatic glycogen concentration (P < 0.01). At a dose of 1 g casein hydrolysate/kg body wt, changes in portal plasma glucagon concentration, phosphorylase a activity and hepatic glycogen concentration generally were not observed. Hepatic glucose, uridine diphosphoglucose, ATP and glucose-6-phosphate concentrations were unaffected by either dose of casein hydrolysate. The data indicate a dose-response relationship between casein hydrolysate administration and effects on glycogen metabolism in the liver. Protein-induced glycogenolysis is likely to occur when rats ingest a moderate amount of a pure protein meal.
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PMID:Physiological doses of oral casein affect hepatic glycogen metabolism in normal food-deprived rats. 773 75

Angiotensin II stimulates the hepatic synthesis and secretion of angiotensinogen, the substrate of renin. In the present study performed on freshly isolated rat hepatocytes we demonstrate that this effect of angiotensin II is mainly related to a transient inhibition of adenylylcyclase. Agents known to decrease intracellular cAMP (angiotensin II, vasopressin, guanfacine) or the cAMP-antagonist Rp-adenosine-3',5'-cyclic phosphothioate stimulated, whereas cAMP-stimulating agents (isoproterenol, forskolin, glucagon) or the cAMP-agonist Sp-adenosine-3',5'-cyclic phosphothioate inhibited angiotensinogen synthesis. In contrast, all agents known to affect intracellular concentrations of calcium, as confirmed in Fura-2-loaded hepatocytes (Bay K 8644, calcimycin, calmidazolium, ionomycin, or methoxamine) failed to influence the synthesis of angiotensinogen. The inhibitory effect of angiotensin II as well as the stimulatory effect of glucagon on cAMP were inversely related to angiotensinogen mRNA and angiotensinogen secretion over a wide concentration range of both peptides. Both the angiotensin II-dependent inhibition of cAMP and the angiotensin II-induced increase in angiotensinogen mRNA were abolished by a pertussis toxin pretreatment. In hepatocyte membranes, pertussis toxin ADP-ribosylated a single protein (approximately 41 kDa) probably representing the alpha-subunit of the Gi-protein, coupling inhibitory receptors to adenylylcyclase. We further show that the increase of angiotensinogen mRNA and secretion mainly represents the result of mRNA stabilization, since in a nuclear run-on assay, angiotensin II pretreatment of hepatocytes does not significantly alter the rate of [32P]UTP incorporation into angiotensinogen mRNA, whereas angiotensin II prolonged the half-life of angiotensinogen mRNA in transcription-arrested as well as in [3H]uridine pulse-labeled hepatocytes about 2.5-fold from 80 to 190 min. It is concluded that angiotensin II induces an increase in angiotensinogen synthesis in hepatocytes by stabilizing of angiotensinogen mRNA and that this effect is mediated through inhibition of adenylylcyclase.
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PMID:Angiotensin II stimulates the synthesis of angiotensinogen in hepatocytes by inhibiting adenylylcyclase activity and stabilizing angiotensinogen mRNA. 822 73

Na(+)-dependent uridine uptake is stimulated in isolated rat liver parenchymal cells by glucagon. This effect is transient, reaches maximum levels of stimulation 10 min after hormone addition, and is dose-dependent. Glucagon action can be mimicked by agents that are able to hyperpolarize the plasma membrane (e.g. monensin) and by dibutyryl cyclic AMP. The effects triggered by glucagon, monensin and dibutyryl cyclic AMP are not additive, suggesting a common mechanism of action. 8-(4-Chloro-phenylthio)adenosine 3':5'-cyclic monophosphate (PCT), a cyclic AMP analogue but also a nucleoside analogue, markedly stimulates Na(+)-dependent uridine uptake in an additive manner to that triggered by monensin, similarly to the effect described for nitrobenzylthioinosine. Considering the roles reported for nucleosides in liver metabolism, the use of PCT as a cyclic AMP analogue should be precluded. Insulin is also about to up-regulate Na(+)-dependent uridine uptake by a mechanism which involves a stable induction of this transport activity at the plasma-membrane level. This is consistent with a mechanism involving synthesis and insertion of more carriers into the plasma membrane. It is concluded that the recently characterized hepatic concentrative nucleoside transporter is under short-term hormonal regulation by glucagon, through mechanisms which involve membrane hyperpolarization, and under long-term control by insulin. This is the first report showing hormonal modulation of the hepatic concentrative nucleoside transporter.
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PMID:Hormonal regulation of concentrative nucleoside transport in liver parenchymal cells. 861 Nov 75

Glucagon-like peptide 1(7-36)amide (GLP-1) is currently under investigation as a possible tool in the treatment of non-insulin-dependent diabetes mellitus. In addition to enhancing nutrient-stimulated insulin release, the peptide also favors glycogen synthesis and glucose use in liver, muscle, and adipose tissue. GLP-1 also activates glycogen synthase a in hepatocytes from both normal and diabetic rats. In the present study, the kinetic aspects of such an activation were investigated in hepatocytes from normal rats and from animals rendered diabetic induced by injection of streptozotocin, either in the adult age (insulin-dependent diabetes mellitus model) or in days 1 or 5 after birth (non-insulin-dependent diabetes mellitus models). GLP-1 increased, in a dose-dependent manner, glycogen synthase a activity in the hepatocytes from all groups studied. The activation of the enzyme reached a steady state within 1 min exposure to GLP-1, which, at 10(-12) M, caused a half-maximal activation. When comparing fed vs. overnight-starved normal rats, a somewhat lower basal activity of glycogen synthase a in fasted animals (P < 0.05) coincided with a greater relative increment in reaction velocity in response to GLP-1. The basal activity of glycogen synthase a and the relative extent of its inhibition by glucagon or activation by insulin and GLP-1 were modulated by the extracellular concentration of D-glucose. The activation of glycogen synthase a by either insulin or GLP-1 resulted not solely in an increase in maximal velocity but also in a decrease in affinity of the enzyme for uridine diphosphate-glucose; in diabetic animals, the capacity of insulin or GLP-1 to increase the maximal velocity and Michaelis-Menten constant were less marked than in normal rats. In conclusion, this study indicates that the GLP-1-induced activation of glycogen synthase a displays attributes of rapidity, sensitivity, and nutritional dependency that are well suited for both participation in the physiological regulation of enzyme activity and therapeutic purpose.
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PMID:Effects of glucagon-like peptide 1 on the kinetics of glycogen synthase a in hepatocytes from normal and diabetic rats. 960 88

To determine whether glucagon affects the plasma concentration of uridine, we administered 100 mL physiological saline containing 1 mg glucagon or 100 mL physiological saline alone intravenously over 1 hour to healthy subjects. Glucagon decreased the plasma concentration of uridine from 5.72 +/- 1.05 to 4.80 +/- 0.60 micromol/L but increased the concentrations of cyclic adenosine monophosphate (cAMP) in plasma and pyruvic acid and lactic acid in blood 59-, 1.4-, and 1.3-fold, respectively. Although glucagon increased urinary excretion of uric acid, it did not affect the plasma concentration of purine bases (hypoxanthine, xanthine, and uric acid) or urinary excretion of oxypurines and uridine, indicating that glucagon does not affect purine degradation and suggesting that glucagon does not affect adenosine triphosphate (ATP) consumption-induced pyrimidine degradation. In contrast, physiological saline did not affect any of the measured variables. These results suggest that glucagon enhanced Na+-dependent uridine uptake from the blood into the cells, since glucagon stimulates Na+-dependent uridine uptake into cells in vitro.
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PMID:Effect of glucagon on the plasma concentration of uridine. 962 69

To determine the effect of amino acids on the plasma level and urinary excretion of uric acid and uridine, 200 mL 12% amino acid solution, and 2 weeks later, 100 mL physiological saline solution containing glucagon (1.2 microg/kg weight), was infused into five healthy men. Both increased the urinary excretion of uric acid and the concentration of glucagon, insulin, and glucose in plasma and pyruvic acid in blood, whereas they decreased the concentration of uridine and inorganic phosphate in plasma. However, neither the amino acid infusion nor glucagon infusion affected the concentration of purine bases (hypoxanthine, xanthine, and uric acid), cyclic adenosine monophosphate (cAMP) in plasma, or lactic acid in blood or the urinary excretion of oxypurines (hypoxanthine and xanthine), uridine, or sodium. These results suggest that glucagon may have an important role in the amino acid-induced increase in urinary excretion of uric acid and decrease in plasma uridine.
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PMID:Effect of amino acids on the plasma concentration and urinary excretion of uric acid and uridine. 1045 68

To examine whether branched-chain amino acids affect the plasma concentration of uridine, we administered branched-chain amino acids (L-isoleucine, 2.85 g, L-leucine 5.71 g, and L-valine, 3.43 g) orally to 6 healthy subjects. Plasma uridine and glucose decreased by 44% and 12%, respectively, together with an increase in plasma isoleucine, leucine, and valine 90 minutes after administration. However, branched-chain amino acids did not affect the plasma concentration and urinary excretion of purine bases (hypoxanthine, xanthine, and uric acid) and uridine or the plasma concentration of insulin, glucagon, and cyclic adenosine monophosphate (cAMP). Since small amounts of regular insulin, which were found to decrease plasma glucose more than the amino acids, did not decrease the plasma concentration of uridine, these results suggest that plasma uridine was decreased by a direct effect of the branched-chain amino acids on the cellular uptake and/or release of uridine.
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PMID:Effect of branched-chain amino acids on the plasma concentration of uridine does not occur via the action of glucagon or insulin. 1064 71

In vitro studies indicate that glucagon-like peptide-1(7-36)-amide (GLP-1) can enhance hepatic glucose uptake. To determine whether GLP-1 increases splanchnic glucose uptake in humans, we studied seven subjects with type 1 diabetes on two occasions. On both occasions, glucose was maintained at approximately 5.5 mmo/l during the night using a variable insulin infusion. On the morning of the study, a somatostatin, glucagon, and growth hormone infusion was started to maintain basal hormone levels. Glucose (containing [3H]glucose) was infused via an intraduodenal tube at a rate of 20 micromol.kg(-1).min(-1). Insulin concentrations were increased to approximately 500 pmol/l while glucose was clamped at approximately 8.8 mmol/l for the next 4 h by means of a variable intravenous glucose infusion labeled with [6,6-2H2]glucose. Surprisingly, the systemic appearance of intraduodenally infused glucose was higher (P = 0.01) during GLP-1 infusion than saline infusion, indicating a lower (P < 0.05) rate of initial splanchnic glucose uptake (1.4 +/- 1.5 vs. 4.8 +/- 0.8 micromol.kg(-1).min(-1)). On the other hand, flux through the hepatic uridine-diphosphate- glucose pool did not differ between study days (14.2 +/- 5.5 vs. 13.0 +/- 4.2 micromol.kg(-1).min(-1)), implying equivalent rates of glycogen synthesis. GLP-1 also impaired (P < 0.05) insulin-induced suppression of endogenous glucose production (6.9 +/- 2.9 vs. 1.3 +/- 1.4 micromol.kg(-1).min(-1)), but caused a time-dependent increase (P < 0.01) in glucose disappearance (93.7 +/- 10.0 vs. 69.3 +/- 6.3 micromol.kg(-1).min(-1); P < 0.01) that was evident only during the final hour of study. We conclude that in the presence of hyperglycemia, hyperinsulinemia, and enterally delivered glucose, GLP-1 increases total body but not splanchnic glucose uptake in humans with type 1 diabetes.
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PMID:Effect of glucagon-like peptide-1(7-36)-amide on initial splanchnic glucose uptake and insulin action in humans with type 1 diabetes. 1124 76


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