CYTOCHROME P450-DEPENDENT ENZYMES AND OXIDANT-MEDIATED RESPONSES IN RAINBOW-TROUT EXPOSED TO CONTAMINATED SEDIMENTS

Hatchery-reared immature rainbow trout (Oncorhynchus mykiss) were expo sed to different concentrations (2 and 4 liters) of contaminated sedim ent taken from a site receiving unbleached pulp mill effluents. The fi sh were held in aquaria and sampled three times during an experimental period of 21 days. The monooxygenase activity, measured as the deethy lation of 7-ethoxyresorufin (EROD activity), increased three- to fourf old in the exposed fish relative to controls. The increase was not dep endent on exposure concentration. Cytochrome P450IA1, the EROD catalys t, demonstrated proportional induction in the 2-liter exposed fish. Ho wever, exposure to 4 liters sediment strongly induced P450IA1 and did not reflect EROD activity. This may suggest inhibition of P450IA1 acti vity by the amount of chemicals discharged from pulp mills. UDPglucuro nosyl-transferase increased at one stage of the experimental period, w hile glutathione S-transferase remained unchanged. Amounts of total gl utathione in blood, liver, and muscle were slightly increased by expos ure to contaminated sediments, but hepatic enzyme activities of supero xide dismutase and catalase were not affected. In conclusion, monooxyg enase activities appear to be a sensitive tool in the monitoring of se diment toxicity. (C) 1994 Academic Press, Inc.