Abstract: We investigated the changes of the expression of antioxidant enzymes and detoxification enzymes and cytochrome P450 3A (CYP3A) in liver tissue of Rana dybowskii after exposure to atrazine and chlorpyrifos in tadpoles stage. Experiments were carried out under different concentrations of atrazine and chlorpyrifos, either alone or combined. The activities of catalase (CAT), superoxide dismutase (SOD), acetylcholinesterase (AChE), carboxylesterase (CbE), and relative expression of CYP3A mRNA were measured in the liver tissue of Rana dybowskii at the period of metamorphosis completion. The results showed that the activities of antioxidant enzymes (SOD and CAT) and detoxification enzymes (AchE and CbE) and relative expression of CYP3A mRNA in the liver tissue were significantly decreased with increasing pesticide concentrations. These results suggested that exposure of to single and combined pesticides at tadpole stage could make Rana dybowskii toxic at the period of metamorphosis completion, and significantly changed the activities of antioxidant enzymes and detoxification enzymes, and relative expression of CYP3A mRNA. The expression of CYP3A mRNA showed similar responses with the levels of antioxidant enzymes and detoxification enzymes.

Key words: Rana dybowskii, antioxidant enzyme, CYP3A, atrazine, chlorpyrifos.