Studies on the role of cAMP-dependent protein kinase in the actions of glucagon and catecholamines on liver glycogen metabolism.
Glucagon causes a rapid activation of cAMP-dependent protein kinase in rat liver parenchymal cells which correlates well with the accumulation of cAMP. Full activation of phosphorylase or inactivation of glycogen synthase is achieved with half-maximal or less activation of protein kinase. Epinephrine stimulates glycogen breakdown in these cells mainly by mechanisms involving alpha-adrenergic receptors and not beta-receptors. Activition of alpha-receptors results in rapid activation of phosphorylase and inactivation of glycogen synthase without accumulation of cAMP or activation of cAMP-dependent protein kinase. Activation of beta-receptors causes a transient rise in cAMP and a short-lived activation of protein kinase with correspondingly little stimulation of glycogenolysis.
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology*; D008112:Liver Glycogen / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D006005:Phosphorylases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism
D008112:Liver Glycogen; D011941:Receptors, Adrenergic; D010656:Phenylephrine; D005934:Glucagon; D000242:Cyclic AMP; D006005:Phosphorylases; D011494:Protein Kinases; D004837:Epinephrine