亚致死剂量铜对蚯蚓P450酶和抗氧化酶活性的长期影响

以赤子爱胜蚓(Eiseniafetida)为供试生物,通过人工污染草甸棕壤的方法,研究了暴露于含有亚致死剂量Cu(100、200、300、400mg·kg-1)的土壤中8周时间内蚯蚓体内细胞色素P450含量、谷胱甘肽转移酶(GST)、超氧化物歧化酶(SOD)及过氧化氢酶(CAT)活性的变化.结果显示,各指标在暴露1周时均无显著变化,但在第8周时各指标均受到显著抑制.P450含量在100mg·kg-1剂量水平下暴露2周时表现出显著的诱导效应;GST、SOD和CAT活性则均在第3周开始表现出显著的诱导效应,且SOD和CAT在100mg·kg-1剂量下即出现诱导现象,而GST则在200mg·kg-1剂量下显现诱导现象.暴露时间大于4周时,P450含量及GST活性开始表现出抑制效应,SOD及CAT活性则在暴露大于6周后显现抑制效应.以上指标对污染物的响应模式为:无显著变化→诱导→抑制.铜是蚯蚓生长的必需元素,蚯蚓自身对Cu的适应机制,以及对铜的长期摄取能危害蚯蚓正常代谢可解释上述响应模式产生的原因.但各指标在对毒性的响应敏感性上存在差异,其中,P450响应最为敏感,而SOD、CAT最不敏感.因此,在生态毒性诊断时,应选择不同指标作为一套指标体系相互补充,以增强污染诊断的灵敏性及长期诊断性.

Long-term effect of copper with sublethal dose on cytochrome P450 and antioxidant enzyme activities of earthworms

Earthworms(Eisenia fetida) as test subjects are exposed to sub-lethal dose(100,200,300 and 400 mg · kg-1) of Copper(Cu) for 8 weeks according to the method of meadow brown soil polluted artificially.At the 1st,2nd,3rd,4th,6th and 8th week,the cytochrome P450,glutathione-s-transferase(GST),superoxide dismutase(SOD) and catalase(CAT) were tested.The results show that the variation of all indices is not significant in the 1st week,while at the 8th week they change significantly.The response behavior of all indices during exposure can be summarized as:insignificant change→induction→inhibition.The reasons for such response behavior are that Cu is the essential metal for earthworms and earthworms have adaptive mechanism for Cu,but absorbing over-dose Cu for long time will do harm to earthworms’ normal metabolism.However,the experimental results show that the response sensitivities of different indexes to Cu are different.The P450 content was the most sensitive index,while SOD and CAT activity were the least.Therefore,the four indices should be used together as a set of biomarkers to improve the sensitivity and efficiency when diagnosing different exposure concentrations.