Effects of Insulin on Calcium Metabolism and Platelet Aggregation

Abstract

The influence of insulin on platelets in vitro has not been exhaustively investigated. To clarify whether insulin affects Ca 2+ metabolism in platelets directly or through alteration of other systems regulating intracellular Ca 2+ homeostasis, we examined the effect of insulin both alone and in combination with prostaglandin E 1 on platelet aggregation and Ca 2+ metabolism. Incubation of rat platelets with insulin reduced thrombin-induced Ca 2+ influx but did not change thrombin-evoked release of Ca 2+ from internal stores or the size of internal Ca 2+ stores. The interactive effects of insulin with prostaglandin E 1 were only additive, and insulin did not augment the effects of prostaglandin E 1 on platelet Ca 2+ metabolism. In contrast, insulin did not inhibit thrombin-induced platelet aggregation but did augment inhibition of platelet aggregation by prostaglandin E 1 . Our results suggest that insulin inhibits platelet function by both prostaglandin E 1 –dependent and -independent mechanisms.