Oxidative damage and changes in Glutathione S-transferase activity in juvenile African catfish, Clarias gariepinus   exposed to cypermethrin and chlorpyrifos

Cypermethrin and chlorpyrifos are broad-spectrum insecticides routinely used as household and agricultural insecticides. Since aquatic environments serve as sinks for numerous environmental pollutants, the effects of these substances on the resident aquatic organisms can be quite serious. In this study, we investigated the effects of exposure of African catfish to cypermethrin and chlorpyrifos on oxidative damage and the activity of glutathione S-transferase (GST). Juvenile African catfish were exposed to 1.25 µg/L cypermethrin, 1.25 µg/L chlorpyrifos, 2.5 µg/L cypermethrin or 2.5 µg/L chlorpyrifos for 96 h. Control fish were maintained in borehole water. At the end of the 96 h exposure, tissue lipid peroxidation (LPO), protein carbonylation and GST activities were determined. Contaminant exposure resulted in a significant increase (p < 0.05) in the levels of LPO and protein carbonylation and the activity of GST in the gills, liver and muscle of exposed fish compared to the controls. Oxidative damage was more serious in the groups exposed to chlorpyrifos compared to those exposed to cypermethrin, thus implying that chlorpyrifos is more toxic to these fish than cypermethrin. The results of this study indicate that the pollution of aquatic ecosystems with cypermethrin and chlorpyrifos may cause oxidation of biomolecules (lipids and proteins) that are involved in essential physiological and biochemical activities in animals.

Keywords
Insecticides; oxidative stress; African catfish; lipid peroxidation; protein carbonylation; GST activity