Effects of simvastatin on (A) endothelial nitric oxide synthase (eNOS) phosphorylation and (B) hydroxyl radical (OH•) formation in activated platelets. (A) Platelets were incubated with prostaglandin E1 (PGE1, 10 μM), simvastatin (30 and 50 μM), or 0.5% DMSO in the absence or presence of SQ22536 (100 μM) or ODQ (20 μM) as described in "Methods". Cells were collected, and subcellular extracts were analyzed for eNOS phosphorylation. Data are presented as the means ± S.E.M. (n = 4); **P < 0.01 and ***P < 0.001, compared to the control group; #P < 0.05, compared to the PGE1 group. (B) For the electron spin resonance (ESR) study, platelets were preincubated with (a) Tyrode's solution (resting group), (b) a solvent control (0.5% DMSO), or simvastatin (30 and 50 μM), followed by the addition of collagen (1 μg/ml) to trigger platelet activation. Spectra are representative examples of four similar experiments. Asterisk (*) indicates the formation of hydroxyl radical.