The activation of Src family tyrosine kinases downstream of PAR stimulation in platelets. Washed and aspirin-treated platelets were stimulated with either SFLLRN (50 μM) or AYPGKF (500 μM) for the different time points at 37°C, and the activation of Src family tyrosine kinases were studied by Western blotting using the phospho-Src (Y416) antibody (A). Washed and aspirin-treated platelets were stimulated with either SFLLRN or AYPGKF in the presence and absence of PP1 (10 μM) or PP2 (10 μM) at 37°C, and the tyrosine phosphorylation of PKCδ was measured (B). PP3 (10 μM) was used as a negative control. Washed and aspirin-treated platelets were stimulated with either SFLLRN or AYPGKF in the presence or absence of 10 μM PP1 or PP2, and the threonine 505 phosphorylation was measured by Western blotting using the phospho-PKCδ (T505) antibody (C). The Western blots shown are representative of experiments performed using 3 different donors.