Channel catfish (Ictalarus punctatus) were exposed to 0, 10, 20, and 40% bleached kraft pulp and paper mill effluent (BKME) for up to two weeks. Fish were sacrificed on days 1, 3, 7, and 14 of exposure. Blood, liver, and gill tissues were assayed for biochemical responses associated with oxidative stress (superoxide dismutase, catalase, and glutathione peroxidase activities and methemoglobin, reduced glutathione, and malondialdehyde concentrations), peroxisome proliferation (palmitoyl-CoA oxidase and lauroyl-CoA oxidase activities) and the mixed-function oxidase system (cytochrome P-450 difference spectra and ethoxyresorufin O-deethylase activities). There were significant dose-related increases in hepatic catalase and ethoxyresorufin O-deethylase activities and significant decreases in hepatic reduced glutathione concentrations. There were also significant increases in lauroyl-CoA oxidase and palmitoyl-CoA oxidases activities, both components of the fatty acid beta-oxidation system and located in peroxisomes. No statistically significant changes were seen in the other components studied. The increases in catalase and the fatty-acid oxidase activities suggest that BKME exposure may have resulted in peroxisome proliferation in catfish hepatic tissue.

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