PHOSPHOLIPASE-A STIMULATION IN TUMOR-CELLS BY SUBTOXIC CONCENTRATION OF TERT-BUTYL HYDROPEROXIDE

Previous studies have shown an increase in the intracellular free arac hidonic acid content associated with a disturbance in phospholipid met abolism in P815 tumor cells exposed to subtoxic concentration of tert- butyl hydroperoxide. The present study was to determine the respective contribution of the major phospholipid-metabolizing enzymes that coul d be involved in this process, The enzymes (phospholipase A, lysophosp holipase, acylCoA:lysophosphatidylcholine acyltransferase and arcylCoA synthetase) were studied under their respective optimal conditions. W hen P815 cells were treated with 50 mu M of tert-butyl hydroperoxide, a significant stimulation (X 2.5) of phospholipase A was observed afte r 15 min of treatment. The activity of the acyltranferase tended to be higher in cells treated by tert-butyl hydroperoxide while the other e nzyme activities (lysophospholipase and acyl CoA synthetase) were not affected, t-BHP did not significantly induce higher levels of lipid pe roxides in P815 cells. These results show that, in the tumor cell line P815, the disturbance of phospholipid and arachidonate metabolism ind uced by t-BHP is linked to phospholipase A, the activation of which se ems independent of oxidative stress.