Enhanced platelet cyclic AMP response to prostaglandin E1 in essential hypertension.

Platelets provide an accessible and homogeneous cellular system for investigative studies on hypertension. Hypertension-associated abnormalities of cyclic adenosine 3',5'-monophosphate (AMP) metabolism were studied in human platelets. Platelets from hypertensive subjects had an enhanced cyclic AMP accumulation response to prostaglandin E1 (twofold increase in prostaglandin E1 sensitivity). The degree of adenylate cyclase activation in response to both prostaglandin E1 (receptor-mediated) and forskolin (non-receptor-mediated) was greater in hypertensive than normotensive subjects, and prostaglandin E1-stimulated and forskolin-stimulated adenylate cyclase activity correlated directly (r = 0.71, p less than 0.001, n = 26). This finding suggests that the catalytic subunit of the enzyme is the rate-limiting step of this hormonal information transduction. Platelets from hypertensive subjects were more sensitive to epinephrine-induced inhibition of the stimulatory effects of prostaglandin E1 on both cyclic AMP accumulation (fourfold) and activation of cyclic AMP-dependent protein kinase. These findings suggest that the enhanced cyclic AMP metabolic response to prostaglandin E1 in platelets from subjects with established essential hypertension may function as a negative feedback mechanism to protect the cells against calcium overload and to reduce their stimulated participation in hemostatic and thrombotic processes.