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.