镉对黑斑蛙精巢细胞色素P450酶及谷胱甘肽转移酶活性的影响

细胞色素P450酶(CYP450)和谷胱甘肽转移酶(GST)是动物体内主要的解毒酶,在外源毒物的转化和代谢过程中具有重要作用.本文在实验条件下, 将健康性成熟黑斑蛙(Rana nigromaculata)暴露于浓度分别为0.005、0.01、0.05、0.1、0.5和1.0 mg·L^-1的Cd溶液中30 d, 采用荧光分光光度法和紫外分光光度法测定精巢组织乙氧基异酚恶唑脱乙基酶(EROD)、红霉素N-脱甲基酶 (ERND)、氨基比林-N-脱甲基醇酶(APND)和谷胱甘肽转移酶(GST)活性,探讨Cd在精巢的可能代谢过程和毒性机理.结果表明, 与对照组比较, EROD和GST酶活性在0.5和1.0 mg·L^-1 Cd处理组被显著抑制; ERND酶活性在0.01~1.0 mg·L^-1 Cd处理组均被显著抑制;而APND酶活性在各处理组响应变化不明显.结果显示, 精巢EROD、ERND和GST对Cd胁迫的敏感性高于APND, 黑斑蛙精巢中EROD、ERND和GST酶活性的响应可用来评价环境中低水平Cd的污染效应.

Effects of cadmium on cytochrome P450 and GST activity in the testis of Rana nigromaculata

The two main anti-oxidation enzymes, cytochrome P450 (CYP 450) and glutathione S-transferase (GST), play an important role in transforming and metabolizing toxicants. To explore the reproductive toxicity and mechanism in testis of Rana nigromaculata by cadmium, the healthy adult frogs were exposed to 0.005, 0.01, 0.05, 0.1, 0.5, 1.0 mg·L^-1 of cadmium, respectively, for 30 days. The activities of 7-ethoxyresorufin-O-deethylase (EROD), erythromycin N-demethylase (ERND), aminopyrence N-demethylase (APND) and glutathione S-transferase (GST) in the testis of Rana nigromaculata were measured by UV spectrophotometry and fluorospectrophotometry. The protein carbonyl content was assessed with 2,4-dinitrophenylhydrazine and the amount of DNA-protein crosslink was assayed with KCI-SDS, and the ROS level in the liver was also detected. The results showed that the EROD and GST activity was inhibited significantly in 0.5 and 1.0 mg·L^-1 cadmium-treated group compared with control group. The ERND activity at the dosages of 0.01, 0.05, 0.1, 0.5 and 1.0 mg·L^-1 all significantly inhibited compared with that of the control, and APND activity did not change in all Cd groups compared to control. These results show that EROD, ERND and GST activity were more sensitive to cadmium than APND activity. This experiment indicated that the EROD, ERND and GST activity in the testis could be used as an alarming index for evaluating the chronic stress of low concentrations of cadmium in the environment.