(A) DCF fluorescence in collagen-stimulated platelets (100%) and in collagen-stimulated platelets added with scalar concentrations (250, 500, and 1,000 U/mL) of catalase. (B) Cytofluorimetric evaluation of oxidation of DCFH-DA–loaded platelets to fluorescent DCF induced by scalar doses of collagen. Data are expressed as the mean fluorescence channel ± SEM of five separate experiments.