Responses of the hepatic glutathione antioxidant defense system and related gene expression in juvenile common carp after chronic treatment with tributyltin.

Recently, residual organotin compounds have generally been recognised as relevant sources of aquatic environmental pollutants. However, the effects of these contaminants on the glutathione (GSH)-antioxidant system of fishes have not been adequately studied. In the current study, the chronic effects of tributyltin (TBT) found within antifouling paints for ships, on the GSH antioxidant system and related gene expression in the liver of juvenile common carp (Cyprinus carpio) were investigated. Fishes were exposed to sub-lethal concentrations of TBT (75 ng/L, 0.75 and 7.5 μg/L) for 15, 30 and 60 days. GSH levels and GSH-related enzymes activities, including glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST), were quantified in the fish liver. The levels of malondialdehyde were also measured as a marker of oxidative damage. In addition, the expression levels of gstp1, gr and gpx1 in common carp chronically exposed to TBT were determined. The results of the current study indicate that chronic exposure of TBT results in reactive oxygen species stress in the liver of common carp, and mRNA expression levels are more sensitive than related enzyme levels. In short, the measured GSH-related indices could potentially be used as molecular indicators for monitoring organotin compounds in the aquatic environment.