EFFECT OF METHYLPREDNISOLONE ON PLASMA-LIPID PEROXIDATION INDUCED BY LIPOPOLYSACCHARIDE

The effects of methylprednisolone succinate (MP) on plasma lipid perox idation, plasma SOD activity and superoxide production in polymorphonu clear leukocytes (PMNs) induced by lipopolysaccharide (LPS) were exami ned in rats in vivo and in vitro. In rats subjected to LPS treatment, plasma phosphatidylcholine hydroperoxide (PCOOH) levels significantly increased, and the plasma Cu,Zn-SOD activity decreased by about 75%. W hen rats were given 30 mg/kg of MP intravenously, MP suppressed the el evation of plasma PCOOH levels and partially inhibited the decrease in plasma Cu,Zn-SOD activity. MP also suppressed PMA-induced superoxide production in PMNs primed by LPS. In in vitro experiments, low concent rations of MP had no effect on NADPH-dependent lipid peroxidation, but 4 mM MP produced 50% inhibition. MP had little effect on PMA-induced superoxide production in PMNs primed by LPS. Moreover, MP hd no radica l-trapping effect on superoxide, hydroxyl radical and stable DPPH radi cal. These results suggest that the suppressive effect of plasma lipid peroxidation by MP is not due to radical-trapping effects or preventi ve anti-oxidation, but may involve the suppression of the lipid chain reaction in liver membrane resulting from PMA-induced superoxide anion s generated by PMNs.