Increased integrin activation, α-granule exocytosis, and aggregation in platelets from GRK6^−/−mice. (A) Platelets from GRK6^−/− and littermate control mice (WT) were stained with fluorophore-conjugated antibodies to either activated α_IIbβ₃ (Jon/A antibody) or P-selectin and measured by flow cytometry. Platelets were stimulated with PAR4-AP, ADP, TxA₂ mimetic (U46619), or convulxin (CVX) at the concentrations indicated (N = 4). (B) Platelets aggregation in response to a PAR4-AP, ADP, U46619, or CVX at the concentrations indicated (N = 4). *Significant difference (P ≤ .05). MFI, mean fluorescence intensity; ns, not significant.