α Granule release is impaired in VAMP-7^−/− platelets. (A) P-selectin expression in resting platelets (top) and in response to 150 μM AYPGKF (bottom) was monitored by flow cytometry in wild-type and VAMP-7^−/− mice. (B) P-selectin expression in response to the indicated concentrations of AYPGKF was monitored by flow cytometry in wild-type (●) and VAMP-7^−/− platelets (○) (*P < .05, **P < .01; n = 3-5). (C) Immunoblot analysis of P-selectin (P-Sel), PF4, vascular endothelial growth factor, TIMP2, and actin (loading control) in wild-type and VAMP-7^−/− platelets demonstrates comparable levels of these α granule cargo. (D) Wild-type and VAMP-7^−/− platelets were exposed to either vehicle (white bars) or 2 μM ADP (gray bars), subsequently stimulated with 150 μM AYPGKF as indicated, and then evaluated for P-selectin expression by flow cytometry (*P < .05, ***P < .001; n = 3). MFI, median fluorescence intensity.