Influence of the antianginal drug trapidil and its derivative AR 12463 on arachidonic acid liberation and thromboxane formation in thrombin-stimulated platelets.

The 5,7-disubstituted s-triazolo(1,5-a)pyrimidines (TPs) trapidil and AR 12463 inhibited the thrombin-induced Thromboxane (TX) formation in washed human platelets in a concentration-dependent manner (Ic50:trapidil 410 mumol/l and AR 12463 9 mumol/l). The arachidonic acid (AA) liberation measured in parallel was unchanged or only reduced to a small extent. The present study shows that the inhibition of TX formation by trapidil and AR 12463 is independent of AA liberation of platelets.