p38, MEK, and Rac1 inhibitors do not affect platelet spreading on fibrinogen. (A) Platelets were preincubated with either 10 μM SB203580, 10 μM PD98059, 20 μM rac 1 inhibitor, NSC23766, or DMSO for 30 minutes at 25°C. Platelets were allowed to spread on fibrinogen-coated slides for 30, 60, and 90 minutes, and were fixed with paraformaldehyde to stop spreading. Platelets were subsequently labeled with FITC-conjugated phalloidin and photographed using a fluorescence microscope. (B) Quantification of area (pixel number) in 4 random fields (mean ± SE; platelet numbers are marked above each column). Statistical analysis performed using Student t test. At all 3 time points, no statistical significance between groups was found.