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 present study was performed to determine whether alterations in fuel reserves or energy substrate utilization might explain the performance decrements that occur in bacterial infections. Male Fisher-Dunning rats were studied at 24, 48, and 72 h after inoculation with Streptococcus pneumoniae. Rats were either sedentary or subjected to a 2-h swimming session at these three time points (N = 10 in each group). A more than 60% reduction (P less than 0.01) in performance capacity was observed on day 3 of infection compared with that in noninfected controls. This infection in the rat is characterized by fever (P less than 0.01), depression of plasma zinc (P less than 0.01) and free fatty acid (FFA) levels (P less than 0.01), inhibition of the two- to threefold increase in fasting ketonemia, and a decreased (NS) insulin:glucagon ratio, indicating a catabolic state. Glycogen stores were reduced in the heart (47%), liver (43%), and skeletal muscles (39%) but not in the carcass. Superimposed exercise resulted in a further reduction but not depletion of liver, muscle, and carcass glycogen stores, a less pronounced lactic acid accumulation, and a lower oxygen debt. However, plasma FFA and ketone body levels were still maintained or even elevated, suggesting that fat is supplied as fuel during swimming exercise in this infection. Thus, results indicate that unavailability of energy substrates or lactacidosis is not limiting for performance capacity during this severe infection.
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PMID:Metabolic responses to swimming exercise in Streptococcus pneumoniae infected rats. 205 98

In an attempt to assess pancreatic glucagon's efficacy at repeatedly reducing food ingestion during differing circadian periods, three groups of 8 rats each were randomly assigned to 4-hr food deprivations beginning at 0800, 1200 or 1600 with light off at 2000. Subjects were then refed following injections of pancreatic glucagon (400 micrograms/kg b.wt. dissolved in DMSO) or vehicle alone every third day (no injection on intervening day). Food intake was measured at 1 and 20 hr following each injection. Following 3 cycles of the above procedure, each animal was again food deprived at the appropriate time, stunned and sacrificed by decapitation. The liver was sampled and glycogen determinations were made. Glucagon suppressed food intake when injected at 1200 (49.6%) and at 1600 (43.1%) but not when given at 2000 (-2.2%). Glycogen content measured after similar deprivation ending at these times was 5.6, 3.9 and 2.0%, respectively. With repeated glucagon injections, the hormone lost its ability to reduce food intake. In a second study, designed to evaluate the role of insulin in glucagon's action, three groups of 6 rats each were given atropine plus glucagon or glucagon or atropine injections alone; food ingestion was then measured one hr later. Atropine alone somewhat decreased eating, however, in combination with glucagon (given 10 min following atropine), no significant decrements in ingestion were achieved. Glucagon injected after saline produced a significant reduction in food intake (62.5%). Since glucagon stimulates insulin release and hyperglycemia; perhaps insulin release is necessary for glucagon's satiety effect.
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PMID:Glucagon, satiety from feeding and liver/pancreatic interactions. 377 54

Glycogen phosphorylase a activity in 7 rat ascites hepatoma cell lines treated with adrenergic agents, phenylephrine, epinephrine and isoproterenol, was investigated as compared with that in freshly isolated rat hepatocytes. Basal phosphorylase activities in hepatoma cells except AH7974 cells were lower than that in hepatocytes. Phosphorylase in hepatoma cells was not activated by any of the agents, while the enzyme activity in hepatocytes was clearly increased in a dose- and time-dependent manner. Phosphorylase in hepatocytes was sensitive to glucagon, but it was found to be insensitive to glucagon in all hepatoma cells. The present results suggest that rat ascites hepatoma cells may escape the glycogenolytic regulation by catecholamines and glucagon.
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PMID:Studies on responsiveness of hepatoma cells to catecholamines. IV. Lack of adrenergic activation of phosphorylase in rat ascites hepatoma cells. 379 26

The aim of this study was to compare the effects of fructose (F) and glucose (G) intake before exercise on oxidation of the ingested substrate, glycogen utilization, work output, and metabolic changes. Ten trained subjects ingested F or G (1 g/kg), both of which were naturally enriched in 13C. After 1 h of rest, they exercised on an ergometer at 61% of their maximal oxygen uptake (VO2 max) for 45 min, which was immediately followed by 15 min at their maximal voluntary output. During the resting hour, blood insulin and glucose were lower (p less than 0.05) and respiratory quotient and blood lactate higher (p less than 0.01) after F. During exercise, the differences disappeared, apart from a transient but moderate (4.3 mmol/l) hypoglycemia after G compared to F. No difference between F and G was observed for uric acid, glycerol, FFA, and glucagon. Glycogen decrements in the vastus lateralis muscle were 67 +/- 9 (F) and 97 +/- 15 (G) mmol/kg, values not significantly different from each other (P greater than 0.05). The maximal voluntary work produced during the last 15 min did not differ between treatments. During the 2 h after sugar ingestion, 30 +/- 3 g of F and 26 +/- 3 g of G were oxidized to 13CO2. These findings indicate that fructose ingested before exercise was utilized at least as well as glucose, allowed a more stable glycemia, and did not modify performance.
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PMID:Oxidation and metabolic effects of fructose or glucose ingested before exercise. 390 79

1. The development of active and inactive phosphorylase was determined in rat liver during the perinatal period. No inactive form could be found in tissues from animals less than 19 days gestation or older than the fifth postnatal day. 2. The regulation of phosphorylase in organ cultures of foetal rat liver was examined. None of the agents examined [glucagon, insulin or dibutyryl cyclic AMP (6-N,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate)] changed the amount of phosphorylase activity. 3. Glycogen concentration in these explants were nevertheless decreased more than twofold by 4h of incubation with glucagon or dibutyryl cyclic AMP. Incubation with insulin for 4h increased the glycogen content twofold. 4. Glycogen synthetase activity was examined in these explants. I-form activity (without glucose 6-phosphate) was found to decrease by a factor of two after 4h of incubation with dibutyryl cyclic AMP, whereas I+D activity (with glucose 6-phosphate) remained nearly constant. Incubation for 4h with insulin increased I-form activity threefold, with only a slight increase in I+D activity. 5. When explants were incubated with insulin followed by addition of dibutyryl cyclic AMP, the effects of insulin on glycogen concentration and glycogen synthetase activity were reversed. 6. These results indicate that the regulation of glycogen synthesis may be the major factor in the hormonal control of glycogen metabolism in neonatal rat liver.
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PMID:Hormonal regulation of glycogen metabolism in neonatal rat liver. 435 17

1. The rates of gluconeogenesis from most substrates tested in the perfused livers of well-fed rats were about half of those obtained in the livers of starved rats. There was no difference for glycerol. 2. A diet low in carbohydrate increased the rates of gluconeogenesis from some substrates but not from all. In general the effects of a low-carbohydrate diet on rat liver are less marked than those on rat kidney cortex. 3. Glycogen was deposited in the livers of starved rats when the perfusion medium contained about 10mm-glucose. The shedding of glucose from the glycogen stores by the well-fed liver was greatly diminished by 10mm-glucose and stopped by 13.3mm-glucose. Livers of well-fed rats that were depleted of their glycogen stores by treatment with phlorrhizin and glucagon synthesized glycogen from glucose. 4. When two gluconeogenic substrates were added to the perfusion medium additive effects occurred only when glycerol was one of the substrates. Lactate and glycerol gave more than additive effects owing to an increased rate of glucose formation from glycerol. 5. Pyruvate also accelerated the conversion of glycerol into glucose, and the accelerating effect of lactate can be attributed to a rapid formation of pyruvate from lactate. 6. Butyrate and oleate at 2mm, which alone are not gluconeogenic, increased the rate of gluconeogenesis from lactate. 7. The acceleration of gluconeogenesis from lactate by glucagon was also found when gluconeogenesis from lactate was stimulated by butyrate and oleate. This finding is not compatible with the view that the primary action of glucagon in promoting gluconeogenesis is an acceleration of lipolysis. 8. The rate of gluconeogenesis from pyruvate at 10mm was only 70% of that at 5mm. This ;inhibition' was abolished by oleate or glucagon.
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PMID:Carbohydrate metabolism of the perfused rat liver. 558 23

The hormonal regulation of glycogen synthase has been studied with isolated perfused hearts that were depleted of 85% of their endogenous glycogen. Glycogen depletion alone promoted a 3-fold activation of glycogen synthase and magnified by 3-fold the response to insulin. Glycogen depletion also facilitated the detection of epinephrine-promoted glycogen synthase inactivation. Hormonal effects on glycogen synthase have been correlated with changes in phosphorylase, phosphorylase kinase, and tissue cAMP levels. Insulin activation of glycogen synthase was observed within 90 s of hormone addition and was maximal by 4 min. A half-maximum effect was obtained at an insulin concentration of 100 microunits/ml. Insulin-dependent activation is reversed by beta-adrenergic agonists, alpha-adrenergic agonists, and glucagon. Each promote the same degree of inactivation and the maximum extent of inactivation produced by each is independent of whether or not the tissue has been stimulated with insulin. beta-Adrenergic agonists and glucagon act via cAMP, alpha-agonists most likely act via intracellular Ca2+ translocation, and insulin action would appear to be independent of either cAMP or Ca2+. The action of epinephrine on cardiac glycogen synthase is mediated by interaction with both alpha- and beta-receptors. As indicated by dose-response curves, receptor occupancy of each occurs to an almost equal extent at suboptimal epinephrine concentrations. Regulation of cardiac glycogen synthase by epinephrine thus is mediated by two second messenger systems which converge to produce the end physiological response.
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PMID:Cyclic AMP-dependent and cyclic AMP-independent antagonism of insulin activation of cardiac glycogen synthase. 627 86

1. Glucagon, adrenaline and dibutyril cyclic AMP increased the release of glucose to the medium during incubation of liver slices from rainbow trout (Salmo gairdneri) while insulin had no effect. 2. Glycogen content decreased only slightly after cyclic AMP addition and even increased in the presence of glucagon and adrenaline. Consequently, the release of glucose was due mainly to gluconeogenesis. 3. This is corroborated by the reduction of glucose liberation in presence of alpha-cyanocinnamate, an inhibitor of gluconeogenesis.
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PMID:Hormonal effects on the liver glucose metabolism in rainbow trout (Salmo gairdneri). 629 Jan 38

Basal heart triacylglycerol (TG) (mumole triacylglycerol/g of dry weight) (- before "in vitro" Langendorff perfusion -) was significantly higher in animals rendered chronically hypertriglyceridaemic (H) by a 63% sucrose-rich diet than in controls (C, standard diet); 28 +/- 2.6 means + SEM vs. 19.3 +/- 1.2; respectively (p less than 0.01). After 40' perfusion with Krebs-Henseleit buffer + 5.5 mM glucose, 2.5 mM Ca++, TG content fell to 14.2 +/- 0.6 in C and 14.9 +/- 1.9 in H (n.S.). Administration of 1 n mol x min-1 of glucagon (Gn) from min 20 to 40 reduced TG to 9.0 +/- 0.5 in C (p less than 0.05). In contrast no effect of Gn was observed in H (TG at min 40: 16.7 +/- 2.5). Glycogen (Gly) content (mumol/g of dry weight) after Gn perfusion fell from 30 +/- 1.9 to 17 +/- 2.1 (p less than 0.01) in C, while again no effect was recorded in H. "In vivo" plasma glucose fractional coefficient disappearance rate was lower (p less than 0.001) in H: 1.01 x 10(-2) +/- 0.09 x 10(-2) vs 2.61 x 10(-2) +/- 0.14 x 10(-2) in C, in spite of H showing hyperinsulin secretion. Hyperinsulinism was further documented by "in vitro" Iri release studies from incubated pancreas pieces. In the absence of glucose (G) from the incubation medium H produced 541 +/- 19.8 mU/mg weight Tissue/20', while C produced 91.2 +/- 12.7 (p less than 0.001). With 100 mg% G, H released 1058 +/- 259 and C 377 +/- 82.5 (p less than 0.001). It is suggested that hyperinsulin secretion plus insulin resistance may account for the above findings.
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PMID:Effect of sucrose diet on insulin secretion in vivo and in vitro and on triglyceride storage and mobilisation of the heart of rats. 633 37

Three stages of development of hepatic glycogen metabolism in the rat were studied. These included the last stage of gestation, in which large scale synthesis and accumulation of glycogen takes place, the perinatal period of glycogenolysis, and the suckling period up to and including weaning. The role of insulin in the regulation of the key rate-limiting enzymes of glycogen synthesis (glycogen synthase) and glycogen breakdown (glycogen phosphorylase) was studied as was the role of the key phosphoprotein phosphatase enzymes that regulate activation of synthase (synthase phosphatase) and inactivation of phosphorylase (phosphorylase phosphatase). Glycogen accumulates in significant quantities on days 20-21 of gestation in the rat (term, 22 days). Associated with this increased rate and amount of glycogen accumulation is an increase in glycogen synthase a and synthase phosphatase and phosphorylase phosphatase activities associated with the endoplasmic reticulum (ER). Concomitantly, fetal insulin levels are elevated as is the insulin to glucagon molar ratio and the synthase a/phosphorylase a ratio. At birth, these hepatic glycogen stores are rapidly degraded, and synthase a levels are diminished, as are ER-associated synthase phosphatase and phosphorylase phosphatase activities. Phosphorylase a levels are markedly elevated at this time as well. Insulin levels are decreased, as is the insulin to glucagon molar ratio. Gradually over a period of 4 weeks after birth, glycogen levels increase in the liver, accompanied by increased ER-associated phosphatase activities and an increased insulin to glucagon molar ratio. The data support a role for increased ambient insulin concentrations in regulation of the periods of active glycogen synthesis and accumulation in pre- and postnatal rat liver. A possible site of action of insulin is the ER and associated phosphoprotein phosphatase activities.
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PMID:Regulation of hepatic glycogen metabolism in pre- and postnatal rats. 640 92


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