Increased secretion in Cdc42^−/− platelets upon activation. (A) Flow cytometric analysis of α_IIbβ₃ integrin activation (binding of JON/A-PE; top panel) and degranulation-dependent P-selectin exposure (bottom panel) in response to the indicated agonists from wild-type (■) or Cdc42^−/− (▩) platelets. U46 indicates U46619. Results are mean fluorescent intensities (MFIs) ± SD of 6 mice per group. P values from left to right: top, *.015; **.008; *.012; ***< .001; *.017; bottom, ***< .001; **.008. (B) Measurement of released PF4 in the supernatant of resting or activated wild-type (■) and Cdc42^−/− (▩) platelets. Results are given as mean PF4 concentration (ng/mL) ± SD (n = 4 per group). P values from left to right: **.003; *.026; *.014; *.011; *.010. (C) Measurement of released ATP (top panel) and serotonin (bottom panel) in the supernatant of resting or activated wild-type (■) and Cdc42^−/− (▩) platelets. Results are given as mean ATP concentration (μM) and mean serotonin concentration (μg/mL) ± SD (n = 4 per group). (Top) P values from left to right: *.012; **.002; *.019; *.015.