Mice lacking platelet PITPs have prolonged tail bleeding time, but no defects in laser-induced in vivo thrombosis. The laser-induced injury model demonstrates normal in vivo thrombosis and platelet secretion in the Pitpα^fl/fl/β^fl/flPf4-Cre⁺ mice. (A) Representative images show platelet accumulation (CD41, red) and P-selectin exposure (green [overlay of red/green is yellow]) 3 minutes after laser-induced injury to the cremaster arterioles. Images are binary representations of 2D confocal fluorescence images overlaid on the bright-field. White arrows indicate the direction of flow; scale bar, 10 μm. (B) Graphs of the CD41⁺ area over time (left, mean ± standard error of the mean), median CD41⁺ area over time (middle), and CD41 peak area (right, lines represent median ± interquartile range). (C) Graphs of the P-selectin–positive area over time (left, mean ± standard error of the mean), the median P-selectin–positive area over time (middle), and P-selectin peak area (right, lines are median ± interquartile range). n = 20 thrombi in 4 wild-type mice and n = 29 thrombi in 4 Pitpα^fl/fl/β^fl/flPf4-Cre⁺ mice. Statistical analysis were performed using a two-tailed Mann-Whitney test. (D,E) Tail bleeding times in mice lacking PITPβ (D) or both PITP isoforms compared with their littermate controls (E). Tail bleeding was normal in mice with platelets lacking PITPβ (NS, Mann-Whitney test; n = 52 for Pitpβ^fl/flPf4-Cre^- mice and n = 58 for Pitpβ^fl/flPf4-Cre⁺ mice). When both PITP isoforms were deleted in platelets, there was a mild increase in bleeding time (P = .0013 using two-tailed Mann-Whitney test; n = 57 for Pitpα^fl/fl/β^fl/flPf4-Cre^- mice and n = 54 for Pitpα^fl/fl/β^fl/flPf4-Cre⁺ mice).