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)

Rat hepatocytes were incubated in monolayer culture, under serum free conditions, for 8 h. Glucagon (10 nM), 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (100 microM) and dexamethasone (100 nM) increased the activity of phosphatidate phosphohydrolase by approx. 2-, 3.6- and 3.3-fold, respectively. Spermine alone had no significant effect. Spermine (2.5 mM) almost completely inhibited the glucagon induced increase in phosphohydrolase activity. It only partially inhibited the dexamethasone and cyclic AMP mediated inductions. Spermidine had no significant effect in this respect. The results are discussed in relation to the known effects of polyamines on glycerolipid synthesis, in particular, and on intermediary metabolism.
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PMID:Spermine antagonises the effects of dexamethasone, glucagon and cyclic AMP in increasing the activity of phosphatidate phosphohydrolase in isolated rat hepatocytes. 302 29

We have analysed the effects of natural aliphatic polyamines on hormonal induction of tyrosine aminotransferase (TAT) in suspensions of hepatocytes isolated from adult fed rats. Glucagon or cyclic AMP derivatives (dibutyryl and 8-bromo) used alone caused a 4-5 fold increase in enzyme activity within 4h. This effect was independent of glucocorticoids, which also increased TAT activity (2.5-fold); when combined, the effects of the two inducers were additive. Spermine and putrescine totally inhibited the hormonally-mediated increase in enzyme activity when added at the onset of incubation with the inducers. Furthermore, polyamines could block the hormonal effect at any time during the course of TAT induction, with, however, a 30 min lag period, suggesting that they must enter the cells. Hepatocytes were indeed shown to take up spermine. At low external concentrations (less than 50 microM), an Na+-dependent, saturable and concentrative mechanism was predominant; at high concentrations (greater than 0.5 mM) transport occurred mainly through a non-saturable, Na+-independent mechanism, building up intracellular concentrations slightly lower than those in the medium. Dose-dependence analysis of the polyamine effect on enzyme induction indicated that half-maximal and maximal inhibition occurred with 0.75 mM- and 2.5 mM-spermine respectively, whereas 2.5mM- and 7.5 mM-putrescine were required respectively to obtain similar effects. Spermidine was much less effective and cadaverine had virtually no effect. None of the polyamines affected the rate of decay of TAT, nor did they directly or indirectly cause enzyme inactivation, indicating that a post-translational modification was unlikely to account for the polyamine effects. Similarly, these effects could not be ascribed to a non-specific inhibition of overall protein synthesis. We conclude that, in hepatocytes, polyamines (or their metabolites) directly interfere with one or several steps controlled by hormones in the synthesis of tyrosine aminotransferase.
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PMID:Inhibition of hormonal induction of tyrosine aminotransferase by polyamines in freshly isolated rat hepatocytes. 613 28

We studied the effects of glucagon and insulin (GI) administration on the inhibition of liver regeneration by acute ethanol treatment after partial hepatectomy (PH) in rats. When ethanol was given 1 hour before PH at 3 gm/kg body wt., [3H] thymidine incorporation into the hepatic DNA 24 hr after PH was significantly inhibited, but it was completely reversed by GI treatment. Although hepatic ornithine decarboxylase (ODC) activity in the ethanol-treated group 4 hr after PH was significantly inhibited, it was completely reversed by GI treatment. The putrescine (PUT) level in the liver 4 hr after PH was decreased by ethanol, but it was increased by GI treatment. At 12 hr after PH, ODC activity was not inhibited and PUT level in the liver was not decreased by ethanol. The levels of spermidine and spermine in the liver 4 hr after PH were unaffected either by ethanol or by GI treatment. Spermidine/spermine-N1 acetyltransferase activity in the liver 4 hr after PH was showed a tendency to increase by ethanol but it was decreased by GI treatment. Difluoromethylornithine, a specific inhibitor of ODC, decreased the level of PUT in the liver, and inhibited [3H] thymidine incorporation. The intraperitotneal administration of PUT significantly increased [3H] thymidine incorporation. The increase in ODC mRNA caused by pH was inhibited by ethanol, but it was completely reversed by GI treatment. SAT mRNA was affected neither by ethanol ner GI treatment. These results suggested that GI treatment was effective on the inhibition of liver regeneration by acute ethanol treatment, and activation of liver regeneration by GI treatment is closely related with ODC induction at the level of transcription.
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PMID:[Effect of glucagon and insulin administration on the inhibition of rat liver regeneration by acute ethanol treatment after partial hepatectomy]. 970 2

In order to find novel bioactive molecules regulating differentiation and hormone secretion of pancreatic endocrine cells, the effects of various substances including purinergic receptor agonists and inhibitors of polyamine biosynthesis were examined in pancreatic islets and several pancreatic cell lines. The nicotinic alpha3beta4 receptor was found to be present and capable of increasing cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) and insulin secretion in mouse pancreatic Beta-TC6 cells. Activation of both nicotinic and muscarinic M(3)/M(4) receptors resulted in reduction of insulin release when compared with stimulation of muscarinic receptor alone in Beta-TC6 cells. In mouse islets, purinergic P2Y(1) and P2Y(6) receptors, which are coupled to Gq proteins, were expressed and appeared to regulate insulin secretion through Ca(2+) mobilization from intracellular stores. Similar results were observed in Beta-TC6 cells. Spermidine, one of polyamines, was found to modulate insulin synthesis and [Ca(2+)](i) in Beta-TC6 cells by use of a specific spermidine synthesis inhibitor, trans-4-methylcyclohexylamine (MCHA). Antizyme, which binds to ornithine decarboxylase (ODC) and thereby reduces the cellular polyamine level, was found to be necessary for conversion of ASPC-1 cells, a pancreatic ductal tumor cell line, into alpha-cells forming the islet-like structure and expressing glucagon gene. These findings help advance our understanding of the complex mechanisms involved in the regulation of pancreatic endocrine cell function and develop new therapeutic agents in diabetes mellitus.
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PMID:[Identification of novel molecules regulating differentiation and hormone secretion and clarification of their functional mechanisms in pancreatic endocrine cells]. 2019 May 22