Inhibition by DEVD-fmk of A23187-induced cleavage of platelet moesin. (A) Platelets were preincubated for 1 hour without inhibitor or with DEVD-fmk (50 μmol/L) and treated for 20 minutes with A23187. The platelet suspensions were lysed by the addition of SDS (with protease inhibitors). Shown is an immunoblot stained with clone 38 antimoesin MoAb. (B) Quantitation of moesin immunoblots. The methods used are the same as in (A), except that platelets were preincubated with varying concentrations of FA-fmk, YVAD-fmk, and DEVD-fmk. Shown are the mean percentages of inhibition (±SEM, n = 4) of moesin cleavage relative to platelets preincubated without inhibitor.