Reduction of adenylate cyclase activity in lysates of human platelets by the alpha-adrenergic component of epinephrine.
The effects of the alpha- and beta-adrenergic components of epinephrine on adenylate cyclase activity were studied in lyastes of human platelets. The beta-adrenergic component increased enzyme activity between 20 and 50%, whereas the alpha-adrenergic component caused a concentration-dependent reduction of adenylate cyclase activity. The maximal inhibition of adenylate cyclase was 50 to 60% with about 100 muM epinephrine; about 1 muM epinephrine caused half-maximal inhibition. The alpha-adrenergic reduction of adenylate cyclase activity appeared to be immediate and was specific for platelets from species in which alpha-adrenergic stimulation caused aggregation. Adenylate cyclase activity measured in the presence of prostaglandins of fluoride was also reduced by the alpha-adrenergic component of epinephrine, but the inhibitory effect was less than on basal activity. In contrast, the 5'-guanylylimidodiphosphate-stimulated enzyme was not affected by stimulation of alpha-adrenergic receptors.
D000255:Adenosine Triphosphate / Q000097:blood; D000262:Adenylyl Cyclases / Q000097:blood*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D001792:Blood Platelets / Q000201:enzymology*; D002474:Cell-Free System; D000242:Cyclic AMP / Q000097:blood / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology*; D005459:Fluorides / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D009638:Norepinephrine / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D011458:Prostaglandins E; D014970:Xanthines; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D005459:Fluorides; D009638:Norepinephrine; D004837:Epinephrine