A comparative study of antioxidant enzyme activities in freshwater and seawater-adapted rainbow trout.

Comparative studies were performed on the antioxidant enzyme activities and thiobarbituric acid reactive substance (TBARS) concentration in liver and red cells of two groups of rainbow trout (Oncorhynchus mykiss). The fish of the first group were cultured in freshwater and the others were adapted to sea-water by by being transferred from freshwater at 5-6 months of age. Catalase (CAT), glutathione peroxidase (GPX), and glutathione S-transferase (GST) activities were significantly higher in hepatic and extrahepatic tissues in both of the fish groups. Superoxide dismutase (SOD) activities were found lower in the seawater-adapted trout than in the freshwater-cultured trout. In both tissues, TBARS were found significantly higher in the seawater-adapted trout than in the freshwater trout. It was also observed that the red cells of the seawater-adapted trout were much more resistant to oxidative stress than the red cells of the freshwater-cultured trout. The results implicate that antioxidant capacities in the seawater-adapted trout and freshwater trout may be related to physical and chemical characteristics of the environment.