Prostaglandin E1 Receptor Binding in Human Blood Platelets Stimulation and Inhibition of Adenylate Cyclase

Abstract

Prostaglandin El , E2 , Fl and. F2 stimulation of adenylate cyclase to produce cyclic Ar~lP was studied in human. blood platelets. L-norepinephrine, an alpha adrenergic agonist in platelets, inhibits the production of cyclic AMP stimulated by PGE1 by increasing the apparent Km of PGE1. This seems to indicate that the I-norepinephrine is decreasing the affinity PGEl has for stimulating adenylate cyclase. Investigations in the mode of action of prostaglandin stimulation of adenylate cyclase revealed a membrane bound receptor site for PGE1 - Binding studies supported by cAMP assays showed that PGE1 and PGE2 may share a co~~on receptor site while ,there may exist a separate PGF receptor site. L-norepinephrine was shown not to affect binding of PGE1, which provides evidence that the inhibition of the alpha-adrenergic agonist may be . directly on the adenylate cyclase system.