Effect of dexamethasone on translocation of PLA₂, 12-LO, and p67phox from cytosol to membrane and activation of Rac-2 following Ab-induced oxidative platelet particle formation. (A) PLA₂ translocation. Cc and Cm refer to control cytosol and membrane after incubation of platelets for 4 hours at 37°C. Pc and Pm refer to cytosol and membrane after incubation with patient anti–GPIIIa49-66 (P) for 4 hours. The next set of experiments measure elution of membrane PLA₂ with dexamethasone. Pcb and Pmb refer to previous Pm incubated an additional 4 hours with buffer alone. Pcd and Pmd refer to the same incubation plus dexamethasone (d). (B) 12-LO translocation. Pc and Pm refer to platelet cytosol and membrane respectively, following 4 hours of incubation with patient anti–GPIIIa49-66 (P). Pcb and Pmb refer to platelet cytosol and membrane fractions of Pm incubated for a further 4-hour incubation in the presence of buffer. Pcd and Pmd refer to the same incubation time in the presence of dexamethasone (n=2). (C, left panel) p67phox translocation. Plts refer to platelet extract. Cc and Cm refer to control cytosol and membrane fractions of platelets after incubation of platelets for 4 hours at 37°C. Ccd and Cmd refer to same incubation with dexamethasone. Pc and Pm are cytosol membrane fractions of platelets treated with patient Ab. Pcd and Pmd are membrane fractions of platelets treated with dexamethasone and patient Ab. (Right panel) Bar graph and SEM is given for n=5. (D) Activation of Rac-2. CO and C30 refer to control IgG at 0 and 30 minutes of incubation. PO, P15, and P30 refer to patient Ab at 0, 15, and 30 minutes. Pd0, Pd15, and Pd30 refer to patient Ab in the presence of dexamethasone (n=4).