中文摘要：

为评估重金属镉（Cd^2＋）对鱼类抗氧化酶活性的影响,本文采用静水生物测试的方法,将尼罗罗非鱼暴露于不同浓度水平（0、0.5、1.5、3.0和6.0 mg/L）的Cd^2＋溶液中,21 d后测定尼罗罗非鱼肌肉、肝脏、肾脏、脾脏和鳃5种组织中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）的活性和谷胱甘肽（GSH）的含量。结果表明：重金属镉对尼罗罗非鱼抗氧化酶活性产生影响。尼罗罗非鱼肝脏组织的SOD、CAT活性和GSH含量显著高于其他4种组织,具有组织特异性。肝脏组织的SOD、CAT活性和GSH含量随着镉浓度的升高呈下降趋势,高浓度组（3.0 mg/L）和极高浓度组（6.0 mg/L）尼罗罗非鱼肝脏组织的SOD活性显著低于对照组（P〈0.05）。肝脏组织中SOD、CAT活性和暴露水体中镉的浓度水平呈现明显的剂量-效应关系。与对照组相比,暴露组尼罗罗非鱼肾脏组织中SOD、CAT活性及GSH含量均处于诱导状态;对于鳃组织而言,SOD、CAT活性呈现低浓度（0.5 mg/L）时被诱导,高浓度时被抑制。不同暴露组尼罗罗非鱼肌肉和脾脏组织中SOD、CAT活性与对照组没有显著性差异（P〉0.05）。

英文摘要：

In order to assess the effects of cadmium on the antioxidant defense system of fish species,the activities of superoxide dismutase（ SOD）,catalase（ CAT） and content of glutathione（ GSH） in muscle,liver,kidney,spleen and gill tissues of Orechromis niloticus exposed to cadmium at concentrations of 0、0. 5、1. 0、3. 0、6. 0 mg / L for 21 days by static experiment test. The results showed that SOD,CAT activity and GSH content in liver tissues were significantly higher than other tissues（ P〈0. 05）. The activity of SOD and CAT,and content of GSH were decreased with cadmium concentration accumulating in liver. There was significantly lower of activities of SOD,CAT and content of GSH in 3. 0 mg / L and 6. 0 mg / L for exposure group than those of in the control group（ P〈0. 05）. At the sametime,SOD and CAT activities and cadmium concentrations showed a strong relationship of stoichiometry with the range of exposure dosages,different induction of cadium to activities of SOD,CAT and content of GSH in liver of Orechromis niloticus juveniles. However,enzyme activities is induced at the concentration of 0. 5 mg / L,which decreased in gill with the increasing concentration of cadmium（ P〈0. 05）. There was no significant difference of SOD and CAT activity between exposure group and the control group in muscle and spleen tissues（ P〈0. 05）.