(A) Washed human platelets were incubated BX-795 (1 μM), SB-203580 (5 μM), or DMSO (vehicle control) followed by stimulation with 2MeSADP (2.5 nM) under stirred conditions for 5 minutes. Platelet proteins were separated using SDS-PAGE and probed for phosphorylation of p38 (Thr180/Tyr182), ERK1/2 (Thr202/Tyr204), and cPLA2 (S505). (B) Washed human platelets were incubated with SB-203580 (5 μM) followed by stimulation with 2MeSADP at various concentrations under stirred conditions for 5 minutes. Platelet proteins were separated using SDS-PAGE and probed for phosphorylation of p38 (Thr180/Tyr182). Actin is loading control. Representative of n≥3 independent experiments. (C, D) Proposed models for ADP-induced activation of cPLA2 and p38.