Evaluation of protective role of selenium on mercury toxicity by superoxide dismutase, catalase and malondialdehyde parameters in Oreochromis niloticus (Linnaeus, 1758)

In this research, to determine toxicity of mercury (Hg) and whether selenium (Se) has any role in protection of this toxicity, it was investigated the alterations in oxidative stress parameters in tissues of Oreochromis niloticus. For this purpose, fish were exposed to 0.01 and 0.05 ppm Hg and 0.01 ppm Hg+0.01 ppm Se and 0.05 ppm Hg+0.05 ppm Se for 4 and 21 days and activities of superoxide dismutase (SOD) and catalase (CAT) and levels of malondialdehyde (MDA) in gill and liver were determined. It was observed significant changes in all analyzed parameters due to tissue, medium concentration and exposure period in the exposure of mercury alone and Hg+Se mixtures. In Hg alone, and in combination with Se especially in their higher medium concentrations, activities of SOD and CAT in the gill and liver significantly increased at 4 days (P？0.05), while they significantly decreased at 21 days (P？0.05). In the exposure of Hg and Hg+Se and in the both tissues, it not determined significant alteration in the MDA levels at 4 days (P？0.05), while they elevated in their higher concentrations at 21 days (P？0.05). In conclusion, it was determined the increases or decreases in activities of SOD and CAT and levels of MDA in O. niloticus were higher in the Hg alone than Hg+Se mixtures and selenium has a protective effect on oxidative toxicity of mercury