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)

Since administration of mannoheptulose induces temporary hyperglycemia, the present study was conducted to elucidate this phenomenon. The results indicate that mannoheptulose stimulates the activity of hepatic fructose-1,6-diphosphatase and phosphoenolpyruvate carboxykinase, and enhances incorporation of alanine into blood glucose and hepatic glycogen. In addition, mannoheptulose increases plasma levels of glucagon and hepatic cyclic AMP concentration. Gluconeogenic effects of mannoheptulose appear to be mediated by glucagon.
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PMID:Gluconeogenic response to mannoheptulose in the rat. 17 18

We have obtained direct evidence that shows the cellular formation and subsequent release of a potent inhibitor (feedback regulator) of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] by adipocytes, upon stimulation with epinephrine. The appearance of such a feedback regulator in adipocytes preceded its release into the medium. During a 30 min incubation, intracellular regulator levels rose rapidly and reached 39-61 units/g of adipocyte at 10 min. Release of inhibitor into the medium increased slowly and was 11-16 units/g of adipocyte at 10 min. Upon continued incubation, the cells at 30 min contained 30-41 units/g of ingibitor, slightly less than the content at 30 min; meanwhile, the medium content rose more than 3-fold. The inhibitor from both locations appeared to have the same characteristics, judging from the purification procedures and the biological activities on hormone-stimulated adenylate cyclase. Adenylate cyclase was inhibited by the feedback regulator in vitro when either epinephrine, corticotropin (ACTH), or glucagon was used as activator. The site of action of this inhibitor is therefore most likely beyond the specific hormone receptors. A new in vitro action of insulin has been found. Insulin, 50-500 microunits/ml, inhibited the formation and release of this factor from isolated rat or hamster adipocytes by 29-81% after these cells were stimulated by hormones that raise intracellular adenosine 3':5'-cyclic monophosphate. This factor enhaced the effect of insulin in lowering the adenosine 3':5'-cyclic monophosphate levels in fresh rat adipocytes. A reduced formation of such a factor may modify the metabolic events in adipocytes, and some as yet unexplained effects of insulin could therefore be linked to the metabolic effects of this factor.
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PMID:Cellular levels of feedback regulator of adenylate cyclase and the effect of epinephrine and insulin. 17 73

Theophylline, glucagon, and SQ-20009 induce a choleresis in the dog characterized by a proportionate increase in erythritol clearance and bile flow, no increase in bile salt excretion, and by an isosmotic solution of similar electrolyte composition. The increment in bile appears to originate at the canaliculus in response to increased cyclic-AMP.
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PMID:Characteristics common to choleretic increments of bile induced by theophylline, glucagon and SQ-20009 in the dog. 17 39

Isolated rat hearts were perfused with hormonal concentrations of glucagon during a hypoxic perfusion to determine whether it would enhance recovery after reoxygenation. Rat hearts were divided into two groups: (1) those perfused with glucose-free Tyrode's solution and (2) those perfused with Tyrode's solution containing glucose. During 3 minutes of exposure to hypoxia both untreated hearts and hearts perfused with glucagon demonstrated a decrease in contractile force to 10-20% of control. When glucose was present in the perfusion medium, cardiac performance was better during both the periods of hypoxia and reoxygenation. During reoxygenation, recovery of contractile force was significantly better (P less than 0.05) in glucagon-perfused hearts than in untreated hearts; this improved recovery occurred regardless of whether glucose was included in the medium. The enhanced recovery of the glucagon-perfused hearts was associated with decreases in myocardial levels of guanosine, 3',5'-monophosphate (cyclic GMP) both during the periods of hypoxia and reoxygenation. At the end of the hypoxic period, cyclic GMP levels in the glucagon-perfused hearts were 20-64% of the levels in untreated hearts. Similarly, after 5 minutes of reoxygenation cyclic GMP levels in the glucagon-perfused hearts were 21% of the levels in the untreated hearts. The effect of glucagon on adenosine 3',5'-monophosphate (cyclic AMP) concentrations in untreated hearts and in hearts receiving glucagon was not significantly different either after 3 minutes of hypoxia or during reoxygenation. The rate of anaerobic glycolysis after 3 minutes of hypoxia was higher in untreated hearts than in glucagon-perfused hearts, as determined by the lactate content of coronary perfusates. These studies suggest that hormonal concentrations of glucagon exert a protective effect on the hypoxic rat heart which involves a modulation of cardiac cyclic GMP accumulation.
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PMID:Changes in cyclic nucleotide levels and contractile force in the isolated hypoxic rat heart during perfusion with glucagon. 17 33

Adenylate cyclase activity was measured in a crude particulate fraction of hyaline cartilage obtained from the xiphoid process of the rat. Bovine parathyroid hormone (PTH) at concentrations as low as 1.3 x 10(-7)M and porcine calcitonin (CT) at concentrations as low as 2.3 x 10(-5)M significantly increased adenylate cyclase activity. Glucagon, prostaglandin E1 (PGE1) and E2 (PG2), and epinephrine at concentrations of 10(-5)M also increased activity, whereas, no increased activity was seen with the additions of somatotrophin (10 mug/ml), PGF1alpha, PGF2alpha, or T3 at 10(-5)M. The combination of doses of PTH and CT, which individually produced maximal responses, was not additive. These data provide evidence that cartilage in growing rats responds directly to PTH and CT.
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PMID:Hormonal responsiveness of adenylate cyclase activity in cartilage. 17 93

The effects of ACTH on 3',5'-cyclic AMP (cAMP) levels and lipolysis were examined on isolated adipocytes incubated in either isosmolar or hyperosmolar media. The ability of ACTH to induce intracellular cAMP accumulation was greatly enhanced by incubating cells in hyperosmolar sucrose (100 to 400 mM) solutions. Hyperosmolar solutions prepared by the addition of either NaCL, glucose or mannitol enhanced the ACTH effect on cAMP to the same extent as did the hyperosmolar sucrose solution, but hyperosmolar urea solutions did not have such an effect. The effect of hyperosmolarity was shown only in cells stimulated by lipolytic hormones, and the effects were still evident in the presence of high concentrations of theophylline, indicating the effect of hyperosmolarity is to facilitate hormone action on the receptor-coupler system of the adipocyte membrane. The action of glucagon on cAMP was augmented much less than the actions of ACTH and isoproterenol. Basal as well as ACTH or exogenous cAMP stimulated lipolysis was lower in hyperosmolar sucrose solutions. Some mechanism by which hyperosmolarity interferes with the metabolic sequence beyond the accumulation of cAMP was suggested.
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PMID:Effects of hyperosmolarity on the cyclic AMP concentration and lipolysis of the adipocyte stimulated by adrenocorticotropic hormone. 17 96

Previous studies of the ability of the immature heart to respond to glucagon have yielded conflicting results. To test the possibility that the apparent discrepancies might be explained in part by species variability, isolated hearts of fetal mice and rats (13-22 days' gestational age) were studied under identical conditions in vitro. Changes in atrial rate and ventricular contractility were measured in spontaneously beating hearts exposed to glucagon, and activation of adenylate cyclase was assayed in cardiac homogenates. In mice of 16 days' gestational age or less, there was no change in heart rate in response to glucagon; at 17-18 days, minimal responsiveness was present; and after 19 days, 10muM glucagon caused an increase in spontaneous atrial rate of 30 +/- 4% (SEM) (P less than 0.001). Measurement of the extent and speed of volume displacement of the isotonically contracting hearts with a specially constructed capacitance transducer revealed that ventricular inotropic responsiveness also appeared after 17-19 days. Cardiac stores of glycogen were reduced in older hearts exposed to glucagon, but not in those aged less than 16 days. In contrast, glucagon failed to activate adenylate cyclase in homogenates of hearts of fetal mice at any age. Furthermore, glucagon failed to elicit an increase in the concentration of cyclic AMP in spontaneously beating hearts that developed tachycardia. Responses in hearts of fetal rats were distinctly different from those in mouse hearts: at no age was there any change in heart rate, strength of contraction, glycogen content, or adenylate cyclase activation. Thus, there are major species differences in cardiac pharmacological maturation. Although the mouse heart develops the ability to increase its rate and strength of contraction and to undergo glycogenolysis in response to glucagon well before birth, the rat heart does not. In addition, there is an apparent disparity in late fetal mouse hearts between the ability of glucagon to induce functional responses and its ability to stimulate adenylate cyclase and increase cyclic AMP levels. It is impossible, of course, to rule out absolutely the possibility that localized increases in a critical cyclic AMP pool were present but too small to measure in the entire tissue. Nevertheless, the most obvious interpretation of our results is that they are compatible with the hypothesis that glucagon may exert some of its hemodynamic effects independently from the adenylate cyclase-cyclic AMP system in the late-fetal mouse heart.
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PMID:Responsiveness to glucagon in fetal hearts. Species variability and apparent disparities between changes in beating, adenylate cyclase activation, and cyclic AMP concentration. 17 87

Both caffeine and theophylline, which were known to be potent inhibitors of cyclic-AMP phosphodiesterase, stimulated the incorporation of myoinositol into phosphatidylinositol in rat liver homogenate. However, cyclic-AMP had no effect. The effect of dibutyryl-cyclic-AMP differed with different concentrations. These results suggest that the stimulation cannot be explained by the increase in the amount of cyclic-AMP. This view was supported by the fact that papaverine, cyclic-AMP phosphodiesterase inhibitor, did not stimulate the incorporation and imidazole, the phosphodiesterase stimulator, did not inhibit the incorporation, and that adenylcyclase stimulators, epinephrine and glucagon, did not stimulate the incorporation.
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PMID:Studies on myoinositol. Effects of caffeine and theophylline on incorporation of myoinositol into phosphatidylinositol in rat liver homogenate. 17 40

We studied nine consecutive hypocalcemic patients with acute pancreatitis to elucidate the mechanism of hypocalcemia. Mean serum ionized calcium, 0.97 mM, was below the normal mean of 1.16 mM (P less than 0.001). Seven of eight patients tested had normal parathyroid hormone levels. All responded to parenteral parathyroid extract by increasing serum ionized calcium and urinary cyclic AMP, indicating parathyroid-hormone-responsive target organs. Calcitonin and glucagon concentrations were increased above normal in some patients, but there was no relation with serum ionized calcium. Parenteral glucagon had no significant effect on serum ionized calcium or calcitonin concentrations. These findings suggest that neither glucagon nor calcitonin was primarily responsible for the hypocalcemia, which did not produce expected increases in serum parathyroid hormone concentrations. Relative parathyroid insufficiency may account for the persistent hypocalcemia frequently observed in patients with acute pancreatitis.
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PMID:Inadequate parathyroid response in acute pancreatitis. 17 71

Insulin (10nM) completely suppressed the stimulation of gluconeogenesis from 2 mM lactate by low concentrations of glucagon (less than or equal to 0.1 nM) or cyclic AMP (less than or equal to 10 muM), but it had no effect on the basal rate of gluconeogenesis in hepatocyctes from fed rats. The effectiveness of insulin diminished as the concentration of these agonists increased, but insulin was able to suppress by 40% the stimulation by a maximally effective concentration of epinephrine (1 muM). The response to glucagon, epinephrine, or insulin was not dependent upon protein synthesis as cycloheximide did not alter their effects. Insulin also suppressed the stimulation by isoproterenol of cyclic GMP. These data are the first demonstration of insulin antagonism to the stimulation of gluconeogenesis by catecholamines. Insulin reduced cyclic AMP levels which had been elevated by low concentrations of glucagon or by 1 muM epinephrine. This supports the hypothesis that the action of insulin to inhibit gluconeogenesis is mediated by the lowering of cyclic AMP levels. However, evidence is presented which indicates that insulin is able to suppress the stimulation of gluconeogenesis by glucagon or epinephrine under conditions where either the agonists or insulin had no measurable effect on cyclic AMP levels. Insulin reduced the glucagon stimulation of gluconeogenesis whether or not extracellular Ca2+ were present, even though insulin only lowered cyclic AMP levels in their presence. Insulin also reduced the stimulation by epinephrine plus propranolol where no significant changes in cyclic AMP were observed without or with insulin. In addition, insulin suppressed gluconeogenesis in cells that had been preincubated with epinephrine for 20 min, even though the cyclic AMP levels had returned to near basal values and were unaffected by insulin. Thus insulin may not need to lower cyclic AMP levels in order to suppress gluconeogenesis.
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PMID:Regulation by insulin of gluconeogenesis in isolated rat hepatocytes. 17 43


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