Activation-dependent platelet degranulation, α_IIbβ₃integrin activation, phosphatidylserine exposure, and aggregation as well as in vitro thrombus formation and tail bleeding time. (A) Flow cytometric analysis of degranulation-dependent P-selectin exposure in platelets from sgk1^+/+ (black bar) and sgk1^−/− (gray bar) mice in response to 10μM ADP, 0.02 U/mL thrombin, 1 μg/mL CVX, and 5 μg/mL CRP. Arithmetic mean ± SEM (n = 6). *P < .05. **P < .01. (B) Flow cytometric analysis of α_IIbβ₃ integrin activation in platelets from sgk1^+/+ (black bar) and sgk1^−/− (gray bar) mice in response to 10μM ADP, 0.02 U/mL thrombin, 1 μg/mL CVX, and 5 μg/mL CRP. Arithmetic mean ± SEM (n = 6). *P < .05. **P < .01. (C) Flow cytometric analysis of phosphatidylserine exposure in platelets from sgk1^+/+ (black bar) and sgk1^−/− (gray bar) mice in response to 1.0 U/mL thrombin, 1 μg/mL CVX, and 0.05 U/mL thrombin + 0.5 μg/mL CVX. (Top) Arithmetic mean ± SEM (n = 9). *P < .05. (Bottom) Representative overlays of annexin-positive sgk1^+/+ (black line) and sgk1^−/− (gray line) platelets. Light gray panels represent isotype controls. (D) Impedance aggregometry after stimulation with different concentrations of CRP (1 and 10 μg/mL), collagen (1 and 5 μg/mL), PAR-4 activating peptide (125 and 500μM), and ADP (2.5 and 10μM). Representative aggregation tracings of sgk1^+/+ (black line) and sgk1^−/− (gray line) mice (n = 4). (E) Thrombus formation in vitro. Whole blood from sgk1^+/+ and sgk1^−/− mice was perfused over a collagen-coated surface for 5 minutes at a shear rate of 1700s⁻¹. Arithmetic mean ± SEM (n = 6; top) and representative phase-contrast images (bottom) of surface coverage. **P < .01. Bar represents 50 μm. (F) Tail bleeding time measured after amputating the tail tip of sgk1^+/+ and sgk1^−/− mice. Each dot represents 1 mouse; black bar represents the mean value.