Abstract: To clarify the effects of atrazine and chlorpyrifos on the activities of antioxidant enzyme and the gene expression of B cell CLL/lymphoma 6B (bcl6b) in muscle of Oryzias latipes, we measured superoxide dismutase (SOD) activity, glutathione peroxidase (GSH-PX) activity, and bcl6b mRNA expression withOryzias latipes being treated by exposure to different concentrations of atrazine and chlorpyrifos alone or together at different periods. The results showed that activities of antioxidant enzyme (SOD, GSH-PX) in muscle of Oryzias latipes significantly decreased with increasing pesticide concentration, while the relative expression of bcl6b mRNA significantly increased. After recovered for 30 days, the activities of both antioxidant enzymes (SOD, GSH-PX) were significantly increased as compared to their counterparts at the end of recovery in the moderate concentration or high concentration group, while the expression of bcl6b mRNA was significantly decreased after recovery. These results suggest that the exposure of Oryzias latip es to single or combined atrazine and chlorpyrifos had toxic effect, causing significant changes in the activities of antioxidant enzyme (SOD, GSH-PX) and the expression of bcl6b mRNA. The expression ofbcl6b mRNA was contrary to the change trend of antioxidant enzyme levels. After the environmental conditions being improved, the activities of those two enzymes and the expression of bcl6b mRNA could be effectively recovered.

Key words: nitrogen addition, nutrient resorption., ecological stoichiometry, multi-element