Arachidonic acid induced platelet aggregation and thromboxane formation is inhibited by OKY-1581

Addition of arachidonic acid (AA) to human platelet rich plasma caused a reversible platelet aggregation and a concomitant formation of thromboxane B2 (TXB2). Both AA-induced platelet aggregation and TXB2 formation were inhibited by OKY-1581 and the amounts of PGE2 and PGF2 alpha formed were correspondingly increased. The formation of 6-keto-PGF1 alpha was smaller and was increased only slightly by OKY-1581. ADP-induced platelet aggregation did not result in the formation of TXB2 and it was inhibited only slightly by OKY-1581. When ADP was added to platelet rich plasma six minutes after the addition of AA, the ADP-induced aggregation was greatly decreased in the presence and absence of OKY-1581. The present study indicates that the AA-induced platelet aggregation is inhibited by OKY-1581 and that OKY-1581 is a specific inhibitor of thromboxane synthesis in platelet rich human plasma.