Toxic effects of chlorpyrifos on antioxidant enzymes and target enzyme acetylcholinesterase interaction in mosquito fish, Gambusia affinis

The recovery effect of chlorpyrifos (CPF) on antioxidant enzymes, locomotor behaviour and the target enzyme acetylcholinesterase (AChE) interaction were studied after exposure to 297 μg L−1 (LC50 for 96 h) in mosquito fish, Gambusia affinis. Activities of the antioxidant enzymes—superoxide dismutase, catalase, glutathione reductase in viscera, and AChE in brain were inhibited at 96 h of exposure. However, induction in lipid peroxidation was observed. The antioxidant levels were restored to near control by 16–18 days. Similarly, swimming speed and AChE were also recovered but comparatively needs longer period. In vitro AChE study indicated that CPF alters the apparent Km values, resulting in a competitive type of inhibition and the inhibitory constant Ki was found to be 4.57 × 10−4 M. The results showed that the organophosphate CPF besides its inhibitory effect on target enzyme AChE also inhibits antioxidant enzymes, which can be used as biomarkers in the pesticide-contaminated aquatic streams.