The effect of superoxide dismutase and catalase on metabolism of 3H-arachidonic acid by washed platelets

Abstract

Previous experiments have suggested that superoxide dismutase (SOD) and catalase (CAT) may inhibit prostaglandin synthesis. The purpose of this study was to determine if these free radical scavengers can alter the metabolism of free arachidonic acid (AA) by the cyclooxygenase and lipoxygenase enzyme systems in platelets. In control experiments washed platelets were incubated with 3H-AA for 5 minutes, extracted and the products separated by reverse phase high pressure liquid chromatography (HPLC). In normal intact platelets 13.5 +/- 0.6% of the radioactivity was found in TxB2, 16.3 +/- 1.4% in HHT, 61.3 +/- 1.1% in 12-HETE and 9.0 +/- 1.0% was unconverted AA. Pre-incubating the platelets for 1 minute with 10 micrograms/ml SOD or CAT or 10 micrograms/ml SOD plus 10 micrograms/ml CAT did not inhibit AA conversion or alter the percent product distribution. Similarly, SOD and CAT had no effect on AA metabolism in broken cells. However, as expected, pretreating platelets with indomethacin blocked TxB2 and HHT formation (P less than .0001). We conclude that SOD and CAT do not inhibit cyclooxygenase or lipoxygenase metabolism of free AA in platelets.