Effect of RhoA inactivation by C3 exoenzyme on platelet F-actin content. Washed platelets were incubated for 4 hours at 37°C with vehicle buffer (“No C3”) or 400 μg/mL of C3. Platelets were then diluted with incubation buffer and stirred for 30 seconds at 37°C in the presence of PGI₂ or TRAP, after which they were fixed and stained with bodipy-phallacidin for quantitation of F-actin as described in Materials and Methods. F-actin content was taken as the mean specific bodipy-phallacidin fluorescence expressed as a percentage of the “No C3” control sample incubated with PGI₂. Data represent means ± SEM of three experiments.