Effects of Insulin on Calcium Metabolism and Platelet Aggregation

The influence of insulin on platelets in vitro has not been exhaustively investigated. To clarify whether insulin affects Calcium () metabolism in platelets directly or through alteration of other systems regulating intracellular Calcium homeostasis, we examined the effect of insulin both alone and in combination with prostaglandin E (1) on platelet aggregation and Calcium metabolism. Incubation of rat platelets with insulin reduced thrombin-induced Calcium influx but did not change thrombin-evoked release of Calcium from internal stores or the size of internal Calcium stores. The interactive effects of insulin with prostaglandin E1, were only additive, and insulin did not augment the effects of prostaglandin E1 on platelet Calcium metabolism. In contrast, insulin did not inhibit thrombin-induced platelet aggregation but did augment inhibition of platelet aggregation by prostaglandin E1. Our results suggest that insulin inhibits platelet function by both prostaglandin E1, -dependent and -independent mechanisms. (Hypertension. 1996;28:209-212.)