EFFECT OF 13-HYDROPEROXY-9,11-OCTADECADIENOIC ACID (13-HPODE) ON ARACHIDONIC-ACID METABOLISM IN RABBIT PLATELETS

1. The effect of 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE) o n the formation of thromboxane (TX) B-2, 12-hydroxy-5,8,10-heptadecatr ienoic acid (HHT) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-H ETE) from exogenous arachidonic acid in washed rabbit platelets was ex amined. 2. 13-HPODE inhibited TXB(2) and HHT formation without affecti ng 12-HETE production. 3. 13-Hydroxy-9,11-octadecadienoic acid which w as produced rapidly from 13-HPODE, did not suppress the formation of T XB(2) and HHT, indicating the requirement of the hydroperoxy moiety fo r the inhibitory effect of 13-HPODE on TXB(2) and HHT formation. 4. Ex periments utilizing mannitol and dimethyl sulfoxide (hydroxy radical s cavengers) revealed that the action of 13-HPODE is not due to hydroxy radicals which are expected to be formed from 13-HPODE. 5. These resul ts suggest that 13-HPODE is a selective inhibitor of platelet cyclo-ox ygenase and may have functional effects within platelets.