Platelet tyrosine phosphorylation in response to CRP-XL. Platelets from an “aa” (A) and a “bb” (B) donor were stimulated with the indicated CRP-XL concentration for 90 seconds and analyzed for tyrosine phosphorylation. Time dependence of tyrosine phosphorylation induced by 5 μg/mL CRP-XL was also determined (E-F). Basal (min) and maximum (max) standard samples were prepared independently. (C-D) Whole-lane tyrosine phosphorylation was quantified by means of densitometry and expressed as a percentage of the maximum sample. The magnitude of tyrosine phosphorylation in 4 “aa” and 4 “bb” platelets was determined and expressed as the mean ± SEM.