Cadmium, copper and cadmium-copper interactions during accumulation, elimination and effects of metals on antioxidant enzyme activities in tissues and organs of Oreochromis niloticus

Oreochromis niloticus were exposed to 0.6, 3.0 and 6.0 mgL-1 Cu and 0.2, 1.0 and 2.0 mgL-1 Cd and 0.6 mgL-1 Cu+ 0.2 mgL-1 Cd, 3.0 mgL-1 Cu+ 1.0 mgL-1 Cd and 6.0 mgL-1 Cu+2.0 mgL-1 Cd mixtures for 15 and 30 days to observe metal accumulation and enzymes activities in tissues. After 15 days of metal accumulation the fish were transferred to clean water for the elimination experiment for 30 days.Copper and cadmium accumulated significantly in all the tissues. Accumulation of copper in the presence of cadmium increased significantly, while the cadmium accumulation decreased in the presence of copper.At high concentration of copper catalase (CAT) activity decreased in gill and liver. The higher exposure concentrations of cadmium for 30 days CAT activity in the kidney, gill and muscle tissues were increased significantly when to control values.In both periods tested, high concentration of copper caused a decrease in liver and an increase in kidney, gill and muscle tissue in süperoxside dismutase (SOD) activity. The higher exposure concentration of cadmium for 15 days tissue SOD activity showed a decrease in the liver and an increase in the kidney.In all the concentrations tested, copper increased glutamate pyruvate transaminase (GPT) activity in all the tissues of O. niloticus. High concentration of cadmium caused a decrease in GPT activity in the liver while it caused an increase in kidney and gill tissues.In all the concentrations tested, copper caused a decrease in glucose-6-phosphate dehydrogenase (G6PD) activity in the liver and kidney while it caused an increase in the gill. Except for gill, G6PD activity of tested tissue showed no change after cadmium exposure but the enzyme activity increased in gill tissue.