Pon2^−/−platelets are procoagulant. (A) Glycoprotein Ibα (GPIbα; platelet marker) and PON2 protein expression in human platelets (hPLT; left panel) and murine platelets (mPLT; right). Endothelial EA.hy 926 (ATCC-No. CRL-2922) served as control. (B) Platelet count (PLT; left graph) and mean platelet volume (MPV; right graph) of Pon2^−/− and WT mice determined from whole-blood samples (n = 58-80). ***P < .0001; Student t test. (C) Plasma membrane PS exposure of Pon2^−/− and WT platelets displayed by flow cytometric analysis of annexin V binding (n = 7-8). **P = .0071; Student t test. (D) Flow cytometric analysis of VWF binding to platelets under basal conditions and upon botrocetin treatment (n = 5). *P = .0367; Student t test. (E) ROS level of platelets determined by H₂DCFDA flow cytometry (n = 3-5). *P = .0192; Student t test. (F-H) Thrombin generation in PRP determined by calibrated automated thrombography. Thrombin generation indicated as ETP, (F) under basal conditions, (G) thrombin-triggered, and (H) TF-triggered (n = 6-13). **P = .0034; ***P = .0007; Student t test. Thrombin-triggered ETP (I) in PPP in the presence of phospholipid vesicles and (J) in PRP upon preincubation with annexin V, anti-TF antibody 21E10 and active site inhibited FVIIa (FVIIai) (n = 6-7). *P < .01 vs indicated group; ###P < .001 vs, respectively, treated WT; $$P < .01 vs WT control; 1-way ANOVA with Bonferroni multiple comparison test. (K) Basal ETP in PRP of BM-transplanted mice (n = 12-13). Adjusted P values are indicated; Kruskal-Wallis test with Dunn multiple comparison test. FITC, fluorescein isothiocyanate; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.