Effects of paraquat on the freshwater fish Channa punctata (Bloch): non-enzymatic antioxidants as biomarkers of exposure.

Paraquat is a quaternary herbicide widely used for broadleaf weed control, which has been known to be a highly toxic compound for humans and animals. Therefore, analysis and development of biomarkers of exposure are undoubtedly valuable in evaluating the toxicity of paraquat contaminated water bodies. The effect of a single exposure of paraquat (1 ppm) for 24 h on various non-enzymatic antioxidants was studied in freshwater fish Channa punctata (Bloch). The levels of the reduced glutathione were significantly reduced in the liver and gill of exposed fish. The total and protein thiol levels were increased in all the tissues of the exposed fish. The non-protein thiol levels were reduced in liver and gill. The levels of ascorbic acid increased in liver. The uric acid level increased significantly in kidney and decreased significantly in gill of the exposed fish. The findings of the present investigation demonstrate the oxidative-stress-inducing potential of the herbicide paraquat in fish. This work indicated the possibility of using non-enzymatic antioxidants as biomarkers of exposure to environmental contamination and subsequent validation as a sensitive system for biomonitoring and ecotoxicological risk assessment.