Effect of ABT-263 on platelet count and residual circulating platelets in vivo. C57BL6 mice were administered ABT-263 (25 mg/kg) or an equal volume of vehicle by oral gavage, and whole blood sampled over a 24-hour time period, as described in “In vivo administration of ABT compounds.” The effect of ABT-263 administration on (A) platelet count, (B) exposure of PS, and expression of (C) GPIbα and (D) GPVI on the surface of circulating platelets was assessed as described in supplemental Methods. Graphs represent the data collected from 6 to 8 independent experiments (mean ± SEM). ns indicates not significant. ***P < .001.