EFFECTS OF REACTIVE OXYGEN SPECIES ON ARACHIDONIC-ACID METABOLISM IN RABBIT PLATELETS

Rabbit platelets were exposed to a reactive oxygen species (ROS) gener ating system (xanthine plus xanthine oxidase) to explore the effect of ROS on the formation of 12-hydroxy-5,8,10,14-eicosatetraenoic acid (1 2-HETE), thromboxane (TX) B2, and 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) from exogenous arachidonic acid. Xanthine plus xanthine oxi dase suppressed the production of 12-HETE, TXB2, and HHT by 65-69%. Th is effect was reversed by addition of catalase to the ROS generating s ystem but not by superoxide dismutase, mannitol, or dimethylsulfoxide, indicating that H2O2 is the responsible metabolite. These results sug gest that H2O2 plays an important role in the regulation of platelet c yclo-oxygenase and lipoxygenase activities.