Inhibition by DEVD-fmk, but not by FA-fmk, of microparticle release from platelets stimulated by (A) A23187 or (B) thrombin plus collagen. Platelets were preincubated as indicated for 1 hour with no inhibitor, FA-fmk, or DEVD-fmk (100 μmol/L in [A] and 25 μmol/L in [B]) and were then treated for the indicated time with A23187 (1 μmol/L) or thrombin (1 U/mL) plus collagen (20 μg/mL). Shown are the mean number of released microparticles (MP) ± SEM (n = 4). The unstimulated values (dashed lines) are not significantly different for platelets preincubated without (shown) and with inhibitors. Microparticle release was significantly inhibited in A23187-stimulated platelets at 3 (*P < .001) and 5 minutes (*P < .01) and in thrombin plus collagen-stimulated platelets at 5 (*P < .008), 10 (*P < .01), and 20 minutes (*P < .01).