title: P2-purinergic control of liver glycogenolysis.
abstract: Purinergic agonists cause a dose-dependent activation of glycogen phosphorylase in isolated rat hepatocytes. Half-maximally effective concentrations are 5 X 10(-7)M for ATP, 2 X 10(-6)M for ADP, and about 5 X 10(-5) M for AMP and adenosine. This potency series indicates the presence of P2-purinergic receptors. The mode of action of ATP appears to be identical with that of the Ca2+-dependent glycogenolytic hormones angiotensin, vasopressin and alpha 1-adrenergic agonists. (1) They all require Ca2+ for phosphorylase activation; (2) they do not increase cyclic AMP levels; (3) they are susceptible to heterologous desensitization by vasopressin and phenylephrine; (4) they lower cyclic AMP concentrations in hepatocytes stimulated by glucagon, most probably mediated by an enhanced phosphodiesterase activity.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology*; D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008112:Liver Glycogen / Q000378:metabolism*; D008297:Male; D006005:Phosphorylases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014667:Vasopressins / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D008112:Liver Glycogen; D014667:Vasopressins; D000242:Cyclic AMP; D006005:Phosphorylases; D000241:Adenosine