In vitro inhibitory effect of SR 27417, a potent platelet-activating factor (PAF) receptor antagonist, on the PAF-induced bovine platelet aggregation

The in vitro inhibitory effect of SR 27417, an antagonist of the platelet a ctivating factor (PAF) receptor, on PAF-induced platelet aggregation was st udied in blood collected from seven healthy Friesien calves. Inhibitory eff ects of SR 27417 were determined at thirteen different concentrations (0.1 - 400 nM) by using the dose-response curves of PAF on calf platelet aggrega tion. In the presence of SR 27417, the maximal slopes of aggregation (%/min ) induced by low and high concentrations of PAF were significantly differen t from the control values obtained without an antagonist at p less than or equal to 0.05 and p less than or equal to 0.01 respectively. In vitro PAF-i nduced calf platelet aggregation was dose-dependently inhibited by SR 27417 . The drug inhibited PAF-induced platelet aggregation in a competitive reve rsible manner (pA(2) = 10.46 +/- 2.36 mol.L-1). In conclusion, the results of our study showed that addition of SR 27417 to bovine platelet in vitro i nhibits PAF-induced platelet aggregation.