N-ethylmaleimide inhibits platelet aggregation and potentiates hydrogen peroxide formation induced by thrombin

The effect of NEM pretreatment on hydrogen peroxide accumulation and aggregation in non stimulated and activated human platelets was studied. It was shown that low concentrations of NEM potentiate hydrogen peroxide formation induced specifically by thrombin. The cooperative effect of NEM with thrombin is dose-dependent and reaches the maximum at 5 microM NEM. Thrombin is particularly effective at low concentrations (0.02-0.1 U). Extracellular Ca2+ significantly increases the NEM effect. Moreover NEM inhibits aggregation both in PRP and in washed platelets, exhibiting the greatest activity in washed platelets stimulated by thrombin.