O₂⁻ production in platelets stimulated with collagen. (A) Time course of O₂⁻ production estimated by lucigenin chemoluminescence in platelets stimulated with 1 μg/mL collagen. Data are expressed as the mean ± SEM of five separate experiments. (B) Bar groups showing O₂⁻production estimated by lucigenin 3 minutes after stimulation with 1 μg/mL collagen in platelets incubated with or without 50 μmol/L DPI or 100 μmol/L ASA. Data are expressed as the mean ± SEM of five separate experiments (*P < .05; **P < .01).