23 PRODUCTION OF H2O2 BY STIMULATED PLATELETS

Human platelets have been shown to release H2O2 when challenged with particulate stimuli. Here we report that platelets stimulated by thrombin also generate H2O2 inside, as detected by the peroxidation of the fluorogenic 2, 7-dichlorofluorescein. The increase of the fluorescence is proportional to the amount of H2O2 generated by platelets. Under our experimental conditions, the fluorescence of intra-platelet 2, 7-dichlorofluorescein is increased by 2-5 folds by stimulation with 1 U/ml of thrombin. Intracellular catalase reduces the extent of H2O2 production or its steady-state concentration. The ability of platelets to produce reduced, reactive oxygen radical species is noteworthy, since they have been found to play a role in pathological process, like the Kawasaki disease (Del Principe et al., FEBS Lett.185:142, 1985).