Mechanism of the stimulation of prostaglandin H synthase and prostacyclin synthase by the antithrombotic and antimetastatic agent, nafazatrom.

Nafazatrom, an antithrombotic and antimetastatic agent containing a pyrazolone functionality, is a reducing substrate for the peroxidase activity of prostaglandin H (PGH) synthase. Nafazatrom inhibits the hydroperoxide-dependent oxidation of phenylbutazone, stimulates the reduction of 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid, and is oxidized by microsomal or purified enzyme preparations from ram seminal vesicles. Consonant with the effects of other peroxidase-reducing substrates, nafazatrom stimulates the oxygenation of arachidonic acid to prostaglandin endoperoxides by the cyclooxygenase component of PGH synthase.

Immunochemical evidence for the involvement of prostaglandin H synthase in hydroperoxide-dependent oxidations by ram seminal vesicle microsomes.

Monoclonal antibodies against prostaglandin H (PGH) synthase have been used to precipitate cyclooxygenase and peroxidase activities from detergent-solubilized preparations of ram seminal vesicle microsomes. Approximately 85% of the solubilized cyclooxygenase activity was precipitated using an excess of anti-PGH synthase antibody; under similar conditions, immunoprecipitation of 60% of the diphenylisobenzofuran peroxidase, 75% of the phenylbutazone peroxidase, and 50% of the epinephrine peroxidase activities occurred. In contrast, less than 10% of the cyclooxygenase or peroxidase activities could be precipitated with nonimmune, control antibody preparations.