Platelet aggregation and exposure of fibrinogen receptors by prostaglandin endoperoxide analogues.

Two stable analogues of prostaglandin endoperoxides9.1 1 -azo-prostanoid III (9-1 1 -azo PGH2) and 9.1 1 -methanoepoxy PGH2 (U4661 9 compound)-caused aggregation of washed human platelets and release of a-granule contents. Platelet aggregation induced by these compounds was potentiated by the addition of purified human fibrinogen in a dose-dependent manner. Incubation of prostaglandin endoperoxide analogues with washed platelets in a nonstirred system exposed fibrinogen receptors. Enzymes that remove adenosine diphosphate (ADP) [apyrase and creatine phosphate in the presence of creatine phosphokinase (CP/CPK)J. adenosine triphosphate (ATP). a competitive antagonist of ADP. and 5’ parafluorosulfonylbenzoyl adenosine (FSBA). an affinity label for ADP binding sites. all blocked platelet aggregation and binding of ‘25l-fibrinogen to platelets stimulated by prostaglandin endoperoxide anaIogues. In contrast. these compounds did not prevent platelet shape change induced by prostaglandin endoper-