Structure and function of platelets produced in vitro in the presence of inhibitors of the Rho/ROCK pathway. (A) Platelets obtained with Y27632 or Tat-C3 or P18 display a normal ultrastructure under electron microscopy but an increased size compared to the untreated control. (B) Platelets produced in serum-free medium with or without inhibitors were activated by thrombin (2 U/mL) and analyzed by flow cytometry. Platelets produced with all 3 inhibitors display a normal response to thrombin activation.