title: Control of glycogen phosphorylase interconversion by phorbol esters, diacylglycerols, Ca2+ and hormones in isolated rat hepatocytes.
abstract: In isolated rat hepatocytes: phosphorylase activation by the ionophore A23187 was enhanced in the presence of tumour-promoting phorbol esters and 1,2- (but not 1,3-) diacylglycerols (dioleoyl- and oleoylacetyl-glycerol), with a similar dose-dependency; the activation of phosphorylase by phenylephrine (1 microM) (but not by vasopressin or glucagon) was inhibited both by tumour-promoting phorbol esters and diacylglycerols, but with a different dose-dependency: complete inhibition was achieved with concentrations of phorbol esters two orders of magnitude lower than those of diacylglycerol; binding of the alpha 1-adrenergic antagonist [3H]prazosin and its displacement by unlabelled prazosin was not significantly affected in the presence of the phorbol esters. The possible involvement of protein kinase C in the control of phosphorylase interconversion is discussed.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D004075:Diglycerides / Q000494:pharmacology*; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005989:Glycerides / Q000494:pharmacology*; D006728:Hormones / Q000494:pharmacology; D066298:In Vitro Techniques; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology*; D010703:Phorbol Esters / Q000494:pharmacology*; D006005:Phosphorylases / Q000378:metabolism*; D011224:Prazosin / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: C011439:1,2-diacylglycerol; D004075:Diglycerides; D005989:Glycerides; D006728:Hormones; D010703:Phorbol Esters; D010656:Phenylephrine; D000001:Calcimycin; D006005:Phosphorylases; D011493:Protein Kinase C; D002118:Calcium; D011224:Prazosin