Mercury accumulation and its effects on GSH-related enzyme activities in tissues of Oreochromis niloticus exposed to mercury, mercury-selenium and mercury-zeolite mixtures

In present study, it was investigated mercury (Hg) toxicity on glutathione-related enzyme systems and Hg accumulation in tissues of Oreochromis niloticus and possible protective effects of selenium (Se) and zeolite on this toxicity. For this purpose fish were exposed to 0.01 and 0.1 mg/L Hg; 0.01 mg/L Hg+0.1 mg/L Se, 0.1 mg/L Hg +1.0 mg/L Se and 0.01 mg/L Hg + 0.1 g/L zeolite, 0.1 mg/L Hg+1.0 g/L zeolite for 7 and 21 days and Hg accumulation, glutathione (GSH) level and activities of glutathione peroxidase (GPx), glutathione -S-transferase (GST) and glutathione reductase in gill, liver and muscle tissues were determined. Hg accumulation in tested all tissues elevated with increasing exposure periods with increasing medium concentrations of Hg alone, Hg+Se and Hg+zeolite mixtures. Hg accumulation in tissues significantly reduced in Hg+Se and Hg+zeolite mixtures than in exposure of Hg alone. Significant alterations in GSH level and GSH-related enzymes activities in exposure of Hg alone, Hg+Se and Hg+zeolite mixtures were observed due to tissues, medium concentrations and exposure peryod. In gill and liver tissues GSH level and GR activity reduced while GPx and GST activities increased. In muscle it was not observed a significant change in other parameters except for the GST. The effect of Hg alone on analyzed all parameters were always higher than in combination with Se and zeolite and the order of their effects found Hg > Hg+zeolite > Hg+Se. Our study showed that selenium and zeolite have a protective effect against toxicity induced by Hg.