ANTIOXIDANT ENZYMES ACTIVITY DURING ACUTE TOXICITY OF CHROMIUM AND CADMIUM TO CHANNA MARULIUS AND WALLAGO ATTU

Acute toxicity tests (96-hr LC50 and lethal concentration) of chromium (Cr) and cadmium (Cd) were conducted with two fish species viz. Channa marulius and Wallago attu. At the end of each trial, the fish were dissected and their organs viz. gills, kidney and liver were isolated for the determination of antioxidant enzymes activity. Cadmium was significantly more toxic than chromium with the mean 96-hr LC50 values of 75.70 ± 0.91 and 94.86 ± 0.96 mg L^-1, respectively. C. marulius was significantly less sensitive than W. attu. Activity of superoxide dismutase increased with increasing metallic ion concentrations in the test mediums for both fish species. However, the activity of catalase and peroxidase decreased by increasing the concentration of metallic ions in the test mediums. The fish kept in control conditions (without metal stress) showed maximum activity of catalase and peroxidase. The fish, C. marulius accumulates significantly higher contents of chromium than cadmium. Among fish organs, liver appeared as a target organ that accumulate significantly higher contents of chromium followed by that of kidney, gills, fins, skin, muscle and bones. The W. attu followed almost the similar trend as that of C. marulius for the accumulation of metals. The accumulation order of metals in fish organs were liver kidney gills fins skin muscle bones for both fish species.