Loss of β3 integrin tyrosine phosphorylation attenuates platelet activation following vascular injury in vivo. Total platelet accumulation and α-granule secretion were monitored following laser-induced injury in mouse cremaster arterioles using fluorescently tagged antibodies against mouse CD41 and P-selectin, respectively. The graphs in panels A-B and D-E show total platelet accumulation (CD41-positive area; A, mean ± SEM; B, median) and α-granule secretion (P-selectin–positive area; D, mean ± SEM; E, median) over time in WT (black circles) and diYF mice (gray triangles). Graphs in panels C and F show peak thrombus (C) and P-selectin–positive (F) areas for WT and diYF mice. The horizontal line and error bars indicate median and interquartile range. For WT, n = 38 thrombi from 7 mice and for diYF n = 41 thrombi from 6 mice. Statistics were calculated using the Mann-Whitney test for nonparametric data.