PAF production by platelets. Platelets were layered on gelatin, fibrinogen, and collagen, and the amount of PAF produced was measured after 1 hour of incubation. Platelets were either incubated in buffer or with 2 mmol/L PMSF for 15 minutes at 37°C to degrade the endogenous acetyl hydrolase activity. (▨) Untreated platelets; (▪) PMSF-treated platelets.