Effect of RhoA inactivation by C3 exoenzyme on platelet adhesion to immobilized fibrinogen. Washed platelets were incubated for 4 hours at 37°C with vehicle buffer (“No C3”) or 400 μg/mL of C3. Then platelets were labeled with BCECF as a fluorescent marker, washed, incubated in fibrinogen-coated microtitre wells for 30 minutes at room temperature, and adhesion was quantitated as described in Materials and Methods. Adhesion is expressed as the percentage of added platelets that adhered. Data represent the means ± SEM of five experiments.