MIXED-FUNCTION OXIDASE ENZYME-ACTIVITY AND OXIDATIVE STRESS IN LAKE TROUT (SALVELINUS-NAMAYCUSH) EXPOSED TO 3,3',4,4',5-PENTACHLOROBIPHENYL(PCB-126)

Juvenile lake trout were intraperitoneally injected with corn oil cont aining nominal concentrations of 0, 0.6, 6.3, or 25 mu g [C-14]-3,3',4 ,4',5-pentachlorobiphenyl (PCB-126) per gram of body weight. The PCB-1 26 accumulated in liver in a dose-dependent manner to a sustained conc entration by 6 weeks and remained elevated for the 30-week experimenta l period. Mixed-function oxidase (MFO) enzyme activity was elevated in the two highest dose groups relative to the control group, but not in the low-dose group throughout the 30 weeks. Oxidative stress, measure d by the thiobarbituric acid reactive substances test, was correlated with ethoxy-resorufin O-deethylase and was elevated in liver of the tw o highest PCB dose groups but not the low-dose group. The activities o f the enzymatic antioxidants superoxide dismutase, catalase, and gluta thione peroxidase were unaffected by PCB-126 exposure. The nonenzymati c antioxidant tocopherol was depleted to approximately 75% of the cont rol concentration in liver of all three PCB-dosed groups. Hepatic asco rbic acid level were not different in any of the treatment groups. Ret inol was depleted by greater than an order of magnitude in liver of th e two highest dose groups but not in the low-dose group. This study de monstrates a correlation between hepatic MFO activity and oxidative st ress in PCB-exposed lake trout. Tocopherol and retinol may be importan t mediators of oxidative stress but additional study is required to co nfirm the antioxidant activity of retinol.