Fig. 6.

LysoPAF induces cAMP elevation in platelets and suppresses thrombin-induces platelet aggregation. A, human platelets (3 × 10⁸/ml) were incubated with the indicated lipid (1 μM) for 2 min. Cells were lysed in IBMX-containing buffer, and cAMP was assayed by competitive immunoassay. Data shown are mean ± S.E.M. and are representative of three experiments with similar results. B, thrombin-induced platelet aggregation in the absence or presence of lysoPAF. Human platelets were incubated with the indicated concentrations of lysoPAF for 2 min before stimulation with α-thrombin (0.03 U/ml) at 37°C under stirring conditions. Platelet aggregation, measured by light transmission, was determined over time. C, thrombin-induced platelet aggregation in the absence or presence of the PKA inhibitors H-89 (5 μM) or KT5720 (5 μM) before stimulation with vehicle or lysoPAF (1 μM). Platelet aggregation was measured as in B. Data shown are representative of two independent experiments with similar results.