p38 MAPK inhibition does not affect integrin-mediated aggregation and adhesion to collagen under flow of freshly isolated and stored murine platelets. (A) PRP stored in the presence of DMSO (vehicle) or SB203580 (40μM) was examined in standard aggregometry after addition of 5μM ADP or 1mM PAR4-AP. (B) Freshly isolated murine PRP was activated with the indicated agonists in the presence or absence of SB203580. Results are representative of 3 separate experiments. (C) Platelets in freshly isolated murine blood were labeled by the addition of an Alexa488-labeled antibody to GPIX. Whole blood, in the presence or absence of SB203580, was perfused over collagen at a shear rate of 1200 seconds. Adhesion and thrombus formation of fluorescently labeled platelets were monitored over time. (Left) Representative images. (Right) Fluorescence intensity (platelet adhesion) measured over time. Results are mean ± SEM; n = 6 (3 different blood preparations).