Inhibition of human platelet thromboxane synthetase by 9,11-azoprosta-5,13-dienoic acid.

The synthetic prostaglandin analog 9,11-azoprosta-5,13-dienoic acid (azo analog I) has been found to be a potent inhibitor of human platelet thromboxane synthetase by three independent analytical methods: electron-capture gas chromatography, radioisotopic thin-layer chromatography, and radioimmunoassay. In the presence of azo analog I, human platelet aggregation induced by either the prostaglandin endoperoxide PGH2 or arachidonic acid was antagonized. The addition of azo analog I shifted the transformation of endoperoxides away from thromboxane synthesis and toward prostaglandin E2 synthesis. The specificity of azo analog I is demonstrated by its selective inhibition of the second wave of either ADP- or epinephrine-induced platelet aggregation. These data indicate that PGH2 must be converted to thromboxane A2 in order to induce human platelet aggregation.