iloprost and diphenyliodonium

Diphenylene iodonium is an inhibitor of the enzyme NADPH-oxidase and prevents the generation of oxygen-derived free radicals in neutrophils (Cross and Jones, 1986). Here we show that diphenylene iodonium (0.25-2 microM) inhibited, according to the dose, thrombin-induced platelet-aggregation in human washed platelets and ADP-induced platelet aggregation in platelet-rich plasma. At the concentrations which inhibited platelet aggregation diphenylene iodonium did not alter platelet concentrations of cAMP or cGMP but enhanced the anti-platelet activity of iloprost, sodium nitroprusside or cultured endothelial cells. These findings highlight the importance of free radicals as platelet pro-aggregatory agents.

Topics: Adenosine Diphosphate; Biphenyl Compounds; Cyclic AMP; Cyclic GMP; Endothelium, Vascular; Free Radicals; Humans; Iloprost; In Vitro Techniques; Leukocytes; NADH, NADPH Oxidoreductases; Nitroprusside; Onium Compounds; Platelet Aggregation; Platelet Aggregation Inhibitors; Thrombin