Effect of 17β-E2 on thrombin-dependent Src activation. Platelet samples were treated with 100 nM 17β-E2 (E2), 0.02 U/mL thrombin (Thr), or 100 nM 17β-E2 plus 0.02 U/mL thrombin (E2+Thr) for increasing times (15, 30, and 60 seconds). Identical amounts of total platelet proteins from each sample were analyzed by immunoblotting with anti–pSrc-Tyr416 antibody. Relative amounts of phosphorylated Src detected in each sample were evaluated by densitometric imaging of the immunoblots, and results are reported in the histogram in the bottom part of the figure. Data are mean ± SEM (n = 3). O.D. indicates optical density.