An assessment of Ah-inducible phase I and phase II enzymatic activities and oxidative stress indices in adult lake trout ( Salvelinus namaycush) from Lake Ontario and Lake Superior

Abstract

Relationships between phase I/mixed function oxidase (MFO) and phase II (UGT) enzymatic activities and the appearance of oxidative stress were investigated in the livers of lake trout collected during 1992–1994 from Lake Ontario and Lake Superior. These lakes represent the most and least contaminated of the Great Lakes, respectively. Despite historically different contaminant profiles, lake trout from Lake Ontario had only marginally greater hepatic MFO activity and equivalent UGT activity when compared to lake trout from Lake Superior. Renal MFO activity was significantly greater in lake trout from Lake Ontario. UGT activity in the kidney was similar in lake trout from the two lakes except for those from Black Bay of Lake Superior, which had significantly lower activity. The Lake Superior population had greater hepatic activites of the enzymatic antioxidants catalase in 2 of the 3 years sampled, greater glutathione peroxidase in 1 of the 3 years sampled, and had consistently greater concentrations of the non-enzymatic antioxidant tocopherol. Tocopherol concentrations and glutathione peroxidase activity were also greater in the kidney of lake trout from Lake Superior. Hepatic and renal ascorbic acid concentrations were not different between the two populations. The predominant vitamin A compounds in lake trout from Lake Superior were retinol based, whereas didehydroretinoids were more predominant in lake trout from Lake Ontario. Total alcohol and esterified concentrations of retinoids were significantly higher in the kidneys of lake trout from Lake Ontario. This suggests a compensatory mechanism, whereby filtered retinol is reabsorbed by cells of the kidney. Lake Ontario lake trout had significantly greater hepatic concentrations of lipid hydroperoxides, a measure of oxidative stress.