Analysis of platelet secretion and TxA₂ production. (A) Flow cytometric analysis of P-selectin exposure in platelets stimulated with the indicated doses of thrombin. Data are expressed as mean fluoresce intensity and are the means ± SD of 4 experiments. *P < .05; **P < .01; ***P < .005. Black bars are WT platelets; white bars are Pyk2-deficient platelets. (B) Analysis of thrombin-induced release of [14C]-serotonin from WT (black bars) and Pyk2-KO (white bars) platelets. The release of serotonin in the supernatant of platelets stimulated with the indicated doses of thrombin for 1 minute is expressed as a percentage of the total incorporated radioactivity on subtraction of the values measured in the supernatant of resting platelets. Data are expressed as means ± SD of 3 different experiments. *P < .05; ***P < .005. (C) Accumulation of TxB₂ in the supernatant of WT (black bars) and Pyk2-KO (white bars) platelets stimulated with the indicated doses of thrombin for 15 minutes. Data are expressed as means ± SD of 3 different experiments. *P < .05; **P < .01