CSPα^−/− platelets have defective dense- and α-granule secretion and integrin activation. (A-H) Washed platelets (50 x 10³/µL) from CSPα^+/+, CSPα^+/−, and CSPα^−/− mice were stimulated with 0.1 U/mL thrombin or 100 ng/mL convulxin for 2 minutes and then incubated with fluorescein isothiocyanate (FITC) anti–P-selectin (A,E), phycoerythrin (PE)-conjugated LAMP-1 (B,F), PE-conjugated Jon/A (C,G), or FITC anti-CD41/61 (D,H) antibodies for 20 minutes at 37°C. Fluorescent intensities were measured by flow cytometry. Shown are representative data and GMFI (mean ± standard error of mean) of 5 independent experiments. Statistical analyses were performed using the Kruskal-Wallis multiple comparison test and corrected using the Dunn multiple comparison test. The significant P values are indicated. (I-K) Platelet-rich plasma (PRP) was isolated and adjusted to a concentration of 100 x 10³/µL from CSPα^+/+, CSPα^+/−, CSPα^−/− mice, and Unc13d^Jinx mice. PRP was stimulated with 0.05 U/mL thrombin (I,J) or 100 ng/mL convulxin (K) over a 10-minute period at 37°C to measure ATP release from the platelets at 2 minutes increments. Data are mean ± standard error of the mean of triplicate measurements and are representative of 3 independent experiments. Statistical analyses were performed using 2-way analysis of variance multiple comparisons and corrected using the Tukey multiple comparison test. Significance: ∗(red) = P ≤ .05 WT vs KO and ∗(black) = P ≤ .05 WT vs HET. HET, heterozygous; KO, knockout.