VARIATION OF HEPATIC-ENZYMES IN 3 SPECIES OF FRESH-WATER FISH FROM PRECAMBRIAN SHIELD LAKES AND THE EFFECT OF CADMIUM EXPOSURE

1. Variation of three antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and effects of Cd exposure in a whole lake experiment on these enzymes were investigated in liver from three freshwater fish species, (Pearl Dace (Semotilus margarita), White Sucker (Catostomus commersoni) and Lake Chaff (Salvelinus namaycush)). 2. Enzymatic activity varied significantly between different lakes in geographical proximity. 3. Other than GPx activity, which was lower in Lake Charr, activities of the three enzymes were not different between the three fish species. 4. Seasonal variation was observed in both CAT and SOD activities. 5. Cd exposure resulted in increased liver concentrations of the metal, but metallothionein protein did not significantly increase. 6. SOD activity in liver of fish exposed to Cd was consistently higher than in liver of fish from reference lakes.