The intrinsic apoptosis pathway is not required for development of the PSL. (A) Annexin V and (B) TMRM-positive platelets and (C) Caspase-3/7 activity after incubation with ABT-737 (0.0625-1 µM) at 37°C for 90 minutes. Platelets from Bak^+/+Bax^+/+, Bak^−/−Bax^fl/fl, Bak^+/+Bax^−/−, and Bak^−/−Bax^{Pf4∆/Pf4∆} mice were washed and counts adjusted before incubation with ABT-737. n = 3 biological replicates per genotype. Data are presented as mean ± standard error of the mean (SEM). One-way ANOVA with Dunnett’s multiple comparison test. (D-I) Murine platelets were stored at RT (22°C) with gentle agitation in 5% plasma for up to 9 days. (D) Annexin V-positive platelets, (E) caspase-3/7 activation (Caspase-Glo assay), (F) TMRM-positive platelets, (G) ATP activity (CellTiter-Glo assay), (H) GPIbα surface expression, and (I) P-selectin exposure were assessed at indicated points by flow cytometry or as otherwise indicated. Platelet counts were adjusted prior storage. Data are presented as mean ± SEM. Caspase activity is presented as ratio/start for each genotype. n = 11 to 12 biological replicates per genotype. Statistical significance between 2 treatment groups was analyzed using an unpaired Student t test with 2-tailed P values. *P < .05; **P < .005; ***P < .001.