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)

(1) A system is described for studying the short-term effects of agents on proinsulin synthesis in vitro, as measured by the incorporation of [3H]leucine into isolated proinsulin. (2) Of the agents tested, glucose has the most marked, and apparently earliest, effect on proinsulin synthesis. (3) The adenyl cyclase system participates in the regulation of proinsulin synthesis since exogenous cyclic AMP, glucagon, and caffeine are stimulatory. When cyclic AMP is added to the medium in the presence of glucose, it is the most potent agent acting on the adenyl cyclase-phosphodiesterase system. (4) The addition of NADPH to isolated rat islets inhibits proinsulin and Bulk Protein synthesis in vitro.
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PMID:Regulation of proinsulin synthesis in isolated rat islets. 0 29

1. The subcellular distribution of adenine nucleotides, acetyl-CoA, CoA, glutamate, 2-oxoglutarate, malate, oxaloacetate, pyruvate, phosphoenolpyruvate, 3-phosphoglycerate, glucose 6-phosphate, aspartate and citrate was studied in isolated hepatocytes in the absence and presence of glucagon by using a modified digitonin procedure for cell fractionation. 2. In the absence of glucagon, the cytosol contains about two-thirds of cellular ATP, some 40-50% of ADP, acetyl-CoA, citrate and phosphoenolpyruvate, more than 75% of total 2-oxoglutarate, glutamate, malate, oxaloacetate, pyruvate, 3-phosphoglycerate and aspartate, and all of glucose 6-phosphate. 3. In the presence of glucagon the cytosolic space shows an increase in the content of malate, phosphoenolpyruvate and 3-phosphoglycerate by more than 60%, and those of aspartate and glucose 6-phosphate rise by about 25%. Other metabolites remain unchanged. After glucagon treatment, cytosolic pyruvate is decreased by 37%, whereas glutamate and 2-oxoglutarate decrease by 70%. The [NAD(+)]/[NADH] ratios calculated from the cytosolic concentrations of the reactants of lactate dehydrogenase and malate dehydrogenase were the same. Glucagon shifts this ratio and also that of the [NADP(+)]/[NADPH] couple towards a more reduced state. 4. In the mitochondrial space glucagon causes an increase in the acetyl-CoA and ATP contents by 25%, and an increase in [phosphoenolpyruvate] by 50%. Other metabolites are not changed by glucagon. Oxaloacetate in the matrix is only slightly decreased after glucagon, yet glutamate and 2-oxoglutarate fall to about 25% of the respective control values. The [NAD(+)]/[NADH] ratios as calculated from the [3-hydroxybutyrate]/[acetoacetate] ratio and from the matrix [malate]/[oxaloacetate] couple are lowered by glucagon, yet in the latter case the values are about tenfold higher than in the former. 5. Glucagon and oleate stimulate gluconeogenesis from lactate to nearly the same extent. Oleate, however, does not produce the changes in cellular 2-oxoglutarate and glutamate as observed with glucagon. 6. The changes of the subcellular metabolite distribution after glucagon are compatible with the proposal that the stimulation of gluconeogenesis results from as yet unknown action(s) of the hormone at the mitochondrial level in concert with its established effects on proteolysis and lipolysis.
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PMID:Effect of glucagon on metabolite compartmentation in isolated rat liver cells during gluconeogenesis from lactate. 19 59

The effect of tolbutamide on pyridine nucleotides and insulin secretion stimulated by aminophylline, 3,5-AMP-dibutyrate or glucagon was studied in pancreatic islets of rats previously treated with 6-aminonicotinamide (6-AN), an inhibitor of pyridine nucleotide synthesis. After being incubated for 60 min in a Krebs-Ringer-Bicarbonate-Buffer in the absence of glucose, pancreatic islets of rats i.p. injected with 35 mg/kg of 6-AN 6 hrs before pancreas removal contained about 30% less NADP and NADPH than did islets of control rats. No changes of NDA or NADH were observed in islets of 6-AN-treated animals. Addition of 16.5 mM glucose led to an increase of NADH, NADPH and a decrease of NADP in islets of both groups of animals; NAD levels remained unchanged. In vitro addition of tolbutamide to islets of control rats did not affect the levels of NADPH or NADP in the presence of 5.5 mM glucose. When 16.5 mM glucose were present, a decrease of NADPH and an increase of NADP was obvious. No effect of tolbutamide on insular NADPH or NADP was observed in islets of rats previously treated with 6-AN be it in the presence of 5.5 or 16.5 mM glucose. In islets of 6-AN-treated rats insulin release in response to aminophylline or 3,5-AMP-dibutyrate in the presence of 5.5 mM glucose was significantly depressed, when compared to islets of untreated controls. Addition of tolbutamide increased insulin release due to aminophylline, 3,5-AMP-dibutyrate or glucagon islets of controls. Tolbutamide alone was without effect. In islets of 6-AN-treated rats aminophylline, 3,5-AMP-dibutyrate or glucagon stimulated insulin release only when tolbutamide was present. Our data suggest that there is no direct interference of tolbutamide with pyridine nucleotides of pancreatic islets, and that tolbutamide increases the secretory response of the beta-cell to aminophylline, 3,5-AMP-dibutyrate or glucagon when insulin release due to these agents is inhibited during decrease of insular NADP and NADPH, caused by 6-AN.
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PMID:Effect of tolbutamide on aminophylline-, 3,5-AMP-dibutyrate- or glucagon-induced insulin release from pancreatic islets after impairment of pyridine nucleotide metabolism caused by 6-aminonicotinamide (6-AN). 24 43

The effect of glucagon on the components of the hepatic microsomal electron transport chain (NADPH oxidase, NADPH cytochrome c reductase (EC 1.6.2.4), cytochrome P-450, and NADPH cytochrome P-450 reductase), and on two representative oxidative pathways (aminopyrine N-demethylation, a type I substrate oxidation; and aniline p-hydroxylation, a type II substrate oxidation) was determined. Microsomes from rats pretreated with glucagon (300 mug/kg per day for 3 days) showed a significant decrease in NADPH oxidation and in aminopyrine N-demethylation with a prolonged hexobarbital sleeping time, and a significant increase in aniline p-hydroxylation. Microsomes from rats pretreated with a lower dose of glucagon (30 mug/kg per day for 3 days) showed a significant decrease in the microsomal N-demethylation of aminopyrine. Glucagon had no effect when added in vitro to microsomes, suggesting that the in vivo effects of glucagon are mediated indirectly in the intact animal.
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PMID:Alterations of hepatic microsomal drug metabolism by glucagon. 81 38

The effects of various nucleosides and nucleotides upon glucagon secretion from the isolated perfused rat pancreas were studied. Increasing glucagon secretion was found with increasing concentrations of exogenous cyclic AMP (2 X 10(-4) M, 2 X 10(-3) M and 1 X 10(-2) M). Stimulation of alpha cell secretion was also found with 2 X 10(-3) M 2'AMP, 3'AMP, 5'AMP, ADP, Adenosine, NADP, and NADPH. One X 10(-3) M cyclic GMP elicited significant glucagon secretion. The pattern of glucagon release was similar in all cases with peak secretion occurring during the 30- to 90-s time period following initiation of the stimulus. No significant increase of glucagon secretion was found in response to ATP, guanosine, 2'GMP, 3'GMP, 5'GMP, GTP, xanthosine, inosine, adenine, xanthine, thymidine, cytidine, ribose, nicotinamide, and uric acid. On the basis of the above results, the structural requirement for stimulation of glucagon secretion appears to be adenine linked to ribose, with phosphate groups being unnecessary. The conclusion of this study is that a new class of compounds capable of stimulating glucagon secretion has been identified, and important questions are thus raised about the mechanism of the action of exogenous cyclic AMP.
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PMID:Nucleotide and nucleoside stimulation of glucagon secretion. 110 53

Injection with pharmacological doses of dexamethasone (5 mg/kg) and/or bovine glucagon (1 mg/kg) exerts pronounced effects on toadfish liver compared with vehicle-treated control fish. Affected parameters include hepatic levels of glycogen and the activities of glutamate dehydrogenase, aspartate aminotransferase, malate dehydrogenase, and enzymes involved in NADPH generation as well as the kinetics of pyruvate kinase. Activities of tyrosine aminotransferase, however, a prime target for hormonal induction in mammals, remain unchanged in Opsanus. In subsequently isolated toadfish hepatocytes, metabolite concentrations and flux through gluconeogenesis are altered as are in vitro responses to epinephrine and catfish glucagon in previously injected fish. Contrary to existing mammalian models, short-term regulation of urea cycle activity can be ruled out for toadfish, since hormone treatments fail to influence the activity of two ornithine-urea cycle enzymes or the rate of hepatocyte-urea synthesis. Treatment-dependent increases in hepatic glutamine synthetase, the unique feeder enzyme for ammonia "nitrogen" in fish urea cycle, indicate a potentially pivotal role for this enzyme in longer-term regulation of ureogenesis.
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PMID:Metabolic actions of glucagon and dexamethasone in liver of the ureogenic teleost Opsanus beta. 160 Dec 63

Rainbow trout, Oncorhynchus mykiss, were used to evaluate the effects of carbohydrate loading on plasma levels of pancreatic hormones and associated changes in metabolic indexes in a carnivorous fish. Glucose (3,000 mg/dl, 10 microliters/g body wt) was injected intraperitoneally into fish (mean wt 54 +/- 5 g) that were killed 0.5-24 h after administration. Glucose injection resulted in hyperglycemia with maximum glucose levels of 306 +/- 13 mg/dl observed 60 min after injection. Glucose administration also resulted in hyperlipidemia. Plasma fatty acids increased twofold in glucose-injected animals. Alterations in plasma metabolites reflected changes in energy stores. Although total lipid concentration was unaffected by glucose injection, lipolytic enzyme activity in the liver was enhanced. Biosynthetic capacity, as indicated by NADPH production from glucose-6-phosphate dehydrogenase, was decreased by glucose injection. Liver glycogen content was reduced in glucose-injected animals 1 h after injection. Glucose injection was attended by increases in the plasma levels of gene II somatostatin-25 (predominant form of pancreatic somatostatin in salmonids) and of glucagon. Insulin levels were initially suppressed after glucose injection. These results indicate that metabolic adjustments caused by glucose administration can be related to the regulatory action of pancreatic hormones. Furthermore, these results suggest that the somatostatin-secreting cells of the trout are sensitive to glucose and that somatostatin-suppressed insulin secretion contributes to the glucose intolerance of trout.
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PMID:Insulin suppression is associated with hypersomatostatinemia and hyperglucagonemia in glucose-injected rainbow trout. 167 8

Adenylate cyclase activity in isolated rat liver plasma membranes was inhibited by NADH in a concentration-dependent manner. Half-maximal inhibition of adenylate cyclase was observed at 120 microM concentration of NADH. The effect of NADH was specific since adenylate cyclase activity was not altered by NAD+, NADP+, NADPH, and nicotinic acid. The ability of NADH to inhibit adenylate cyclase was not altered when the enzyme was stimulated by activating the cyclase was not altered when the enzyme was stimulated by activating the Gs regulatory element with either glucagon or cholera toxin. Similarly, inhibition of Gi function by pertussis toxin treatment of membranes did not attenuate the ability of NADH to inhibit adenylate cyclase activity. Inhibition of adenylate cyclase activity to the same extent in the presence and absence of the Gpp (NH) p suggested that NADH directly affects the catalytic subunit. This notion was confirmed by the finding that NADH also inhibited solubilized adenylate cyclase in the absence of Gpp (NH)p. Kinetic analysis of the NADH-mediated inhibition suggested that NADH competes with ATP to inhibit adenylate cyclase; in the presence of NADH (1 mM) the Km for ATP was increased from 0.24 +/- 0.02 mM to 0.44 +/- 0.08 mM with no change in Vmax. This observation and the inability of high NADH concentrations to completely inhibit the enzyme suggest that NADH interacts at a site(s) on the enzyme to increase the Km for ATP by 2-fold and this inhibitory effect is overcome at high ATP concentrations.
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PMID:Inhibition of hepatic adenylate cyclase by NADH. 187

Administration of catecholamines to rats or their addition to liver and heart homogenates activates (by 30-50%) mitochondrial transhydrogenase in the direction of hydride-ion transfer NADPH----NAD+ via beta-adrenoreceptors and cAMP. Glucagon administration also increases by 48% the transhydrogenase activity of liver mitochondria. cAMP (1 microM) incubated with both liver homogenates and mitochondria exerts an independent activating effect on transhydrogenase. The effect of cAMP is specific and is expressed as an increase of V. The integrity of mitochondrial membranes is crucial for the manifestation of cAMP effect. Possible mechanisms of cAMP action on the transhydrogenase activity and the significance of this regulation for mitochondrial energetics are discussed.
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PMID:[Regulation of mitochondrial transhydrogenase activity by catecholamines]. 287 44

Vasoactive intestinal peptide (VIP) has been identified in ovarian nerves and stimulates steroid secretion from immature ovaries. To gain insight into its mechanism of action, the effect of VIP on the synthesis of the cholesterol side-chain cleavage enzyme complex was studied in ovarian granulosa cells from immature estrogen-primed rats. The cells were cultured for 48 hr in serum-free medium; the proteins were labeled with [35S]methionine; and the synthesis of cytochrome P-450, iron-sulfur protein, and NADPH:iron-sulfur protein reductase was evaluated by electrophoretic analysis after immunoisolation with polyclonal antibodies directed against the bovine adrenal enzymes. VIP at concentrations ranging from 0.001 to 1 microM stimulated 3- to 5-fold the synthesis of cytochrome P-450 and iron-sulfur protein. Peptide NH2-terminal histidine, COOH-terminal isoleucine, which has greater than 50% sequence homology of VIP, stimulated the synthesis of both proteins at approximately 50% of VIP effectiveness. Secretin, another member of the glucagon-secretin family of peptides, which has only 30% sequence homology to VIP, was without effect. Similar results were observed with the NADPH:iron-sulfur protein reductase. VIP-induced synthesis of the cholesterol side-chain cleavage enzyme complex was accompanied by a dose-related increase in cAMP accumulation and progestin formation. It is concluded that VIP regulates the synthesis of the ovarian cholesterol side-chain cleavage enzyme complex, which catalyzes the rate-limiting reaction in progesterone biosynthesis, and that the VIP effect is at least partially mediated through cAMP. It is suggested that a stimulatory action of VIP on the synthesis of ovarian progesterone may contribute to regulating the functional development of the ovary.
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PMID:Vasoactive intestinal peptide induces the synthesis of the cholesterol side-chain cleavage enzyme complex in cultured rat ovarian granulosa cells. 302 May 46


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