3,3',4,4'-tetrachlorobiphenyl effects on antioxidant enzymes and glutathione status in different tissues of rainbow trout.

Polychlorinated biphenyls are known to cause induction in cytochrome P450-dependent monooxygenase activities and alteration in the antioxidant defense of mammals. To determine whether similar detoxication processes are activated in rainbow trout (Oncorhynchus mykiss), we investigated P450-dependent enzyme activities, antioxidant enzymes and glutathione status (reduced and oxidized glutathione, GSH and GSSG) in this species injected intraperitoneally with 3,3',4,4'-tetrachlorobiphenyl at 5 mg/kg body weight 6 weeks post injection. Ethoxyresorufin O-deethylase activities increased 11- and 40-fold in liver and kidney. UDPglucuronosyltransferase activities were 2- and 5-fold higher in these organs, while glutathione S-transferase activity was enhanced greater than 2-fold in liver of tetrachlorobiphenyl injected trout in comparison with controls. Glutathione peroxidase activities were increased in liver and white muscle of dosed fish. Tetrachlorobiphenyl exposure resulted in a significant increase in glutathione reductase activities, with 7-fold enhancement in liver and significantly elevated activities in kidney, red and white muscles. Similarly, cytosolic superoxide dismutase and catalase activities were increased in white muscle of injected trout. Tetrachlorobiphenyl exposure significantly increased GSH concentrations in liver and kidney, while GSSG levels were increased in liver and blood plasma. These changes, however, did not modify the GSSG/GSH ratios in these tissues. Overall, these results imply a major tetrachlorobiphenyl effect on GSH status and antioxidant enzymes in trout tissues and identify white muscle along with liver and kidney as important tissues in the detoxication process in this animal.