Abstract:In order to study the toxic effects of diethyl phthalate (DEP) on fish for biomarkers, the carps ([WTBX]Cyprinus carpio[WTBZ] Linnaeus) were exposed to 0.125(T1), 0.5(T2), 2.0(T3) and 8.0(T4) mg·L-1 of DEP for 2 and 20 days, respectively, with water and tween-80 as controls. The effects of DEP on antioxidant defense system and injury indicators in kidney and energy metabolism enzymes in gill were carried out. And the tissue structures of kidney and gill were observed through conventional histological sections and HE staining techniques. The results indicated that there were no obvious differences of anti-hydroxyl radical ability and MDA content in DEP treatment groups compared with the control groups when exposed for 2 days. However, GSH-PX activities and anti-superoxide anion radical ability at each treatment group and SOD activities at T3 and T4 groups and CAT activities at T1 group increased significantly. CAT activities at T3 and T4 groups decreased markedly. Meanwhile, there were no obvious changes in MAO activities of kidney at each treatment group. But activities of ATPase in gill of each DEP treatment group and LDH in gill at T2, T3 and T4 groups and contents of CRE in serum at T3 and T4 increased significantly. When exposed for 20 days, anti-superoxide anion radical ability at T2 and T3 DEP groups, SOD and GSH-PX activities at T1 and MDA contents at T2, T3 and T4 groups increased significantly. CAT activities at every treatment group, anti-hydroxyl radical ability at T3 and T4, anti-superoxide anion radical ability and GSH-PX and SOD activities at T4 were inhibited remarkably. The results also show that,, there were no significant differences in ATPase activities in gill at all treatment groups. However, LDH activities in gill at each DEP treatment group and CRE contents in serum at T2, T3 and T4 groups increased significantly, and MAO activity in kidney at T3 and T4 decreased obviously. At the same time, the gill at T4 group and the kidney at T3 and T4 groups were damaged. This study could provide a theoretic evidence for the evaluation of ecological risk to water environments and biomarkers of DEP.