Platelets in Acute Ischemic Heart Disease

Treatment of normal platelet-rich plasma with a physiological amount of insulin (100 microunits/ml, optimum concentration) for 3 hours at 23°C stimulated the binding of prostaglandin E1 by more than twofold (3,940±250 sites/108 platelets) compared with the nontreated, control platelet-rich plasma (1,590±265 sites/108 platelets). After platelet-rich plasma from patients with acute ischemic heart disease (n=43), whose platelets showed impaired prostaglandin E,/12 receptor activity (850±100 sites/108 platelets), was incubated with insulin (optimum amounts varied from 100 to 200 microunits/ml), the binding of the prostanoid was restored to normal levels (1,790±140 sites/108 platelets) in 75% of the cases. Twenty-five percent of the patients did not respond to the stimulatory effect of insulin. The increased binding of the prostanoid to the insulin-treated platelets also resulted in increased cyclic AMP levels both in normal subjects (44.14+±3.1 pmol/108 [insulin-treated] platelets versus 16.35+±2.91 pmol/108 [control] platelets) and in patients with acute ischemic heart disease (23.87±4.1 pmolIl08 [insulin-treated] platelets versus 7.70±2.0 pmol/108 [control] platelets) by the prostanoid (1.0 ,uM). The treatment of platelet-rich plasma with the hormone decreased the minimum inhibitory concentration of the prostanoid from 34± 14 to 15±9 nM (p<0.001) in the case of normal volunteers and from 49± 15 to 32+11 nM (p =0.002) in the case of "responder" patients. Insulin did not produce any effect on the inhibition of platelet aggregation by the prostaglandin in "nonresponder" patients. In the follow-up study, although the stimulatory effects of insulin on platelets from responder patients were improved to normal levels, the platelets from the nonresponder patients remained persistently unresponsive to the effect of the hormone. (Circulation Research 1991;68:245-254)