Effects On Antioxidant Defense System And Lipid Peroxidation Of Nemertean, Cephalothrix Simula By Heavy Metals

Cephalothrix simula(Iwata) is one of the most common nemertean along the coast of Qingdao.In present study,the nemertean were exposed in copper(Cu) ion solutions at concentration of 0.005,0.018,0.056 mg/l,and zinc(Zn) ion solutions at concentration of 0.14,0.43,1.35 mg/l,cadmium(Cd) ion solutions at concentration of 0.5,1.6,5.0 mg/l for 96 h.Then heavy metal accumulation in vivo,variations of antioxidant enzyme activities,metallothionein(MT) contents and malondialdehyde (MDA) contents of the nemertean were determined respectively.The aim is to explore the effects of heavy metals on the antioxidant defense system and lipid peroxidation of the nemertean,and then accumulate the knowledge that the nemertean was used as a bioindicator to monitor heavy metal pollutants.The results are as follows.The results of heavy metal accumulation in vivo showed that positive correlation existed between the contents of metal ions in vivo and in exposed solutions,and in groups of higher concentrations of ion solutions,the contents of metal ions in vivo were more than the lower ones.In addition,a linear correlation appeared between the contents of metal ions in vivo and the exposed time,the contents of metal ions in vivo were increased by exposed time extended.When the nemertean were exposed in 0.006 mg/l Cu²⁺ solutions,the significant increase of Cu concentrations in vivo appeared at 24 h(p＜0.05),while in 0.018 and 0.056 mg/l Cu²⁺ solutions,it appeared at 12 and 6 h(p＜0.05).Similarly,in Zn²⁺ treatment groups,the significant increase appeared at 24,12 and 6 h(p＜0.05).But in Cd²⁺ treatment groups,it all appeared at 6 h(p＜0.05).The data revealed that the nemertean C.simula has a high ability to accumulate Cu,Zn and Cd,especially Cd. Determination of the activities of CAT,SOD and GPX of C.simula illustrated that activities of CAT,SOD and GPX showed distinct changes at 6-12 h(p＜0.05) except for GPX in groups of 0.006 and 0.018 mg/l Cu²⁺ treatment.CAT was significantly inhibited by the three heavy metal ions and its activity reached the nadir level at 6 or 12 h(p＜0.05) before it started to increase.SOD activities were significantly increased within 48 h in a Cu²⁺ solution,it was only induced after 24 h in Zn solutions.However,it was inhibited before 72 h in Cd²⁺ solutions.Additionally, the activity of GPX reached maximum at 24 h in Cu²⁺ solution and at 6 h in Zn²⁺ solution,but it was significantly inhibited at 6 or 12 h in Cd²⁺ solution.These results revealed that CAT,SOD and GPX of C.simula are sensitive to Cu,Zn and Cd ions in vivo,especially CAT,which might be considered as a biomarker of Cu,Zn and Cd monitor within short time.Variations of MT contents demonstrated MT was significantly induced by three heavy metal ions and at the same time in groups of higher concentrations of metal solutions the contents of MT in vivo were induced more than the lower ones.In groups of 0.018 and 0.056 mg/l Cu²⁺ solutions,MT contents increased fast and got the highest points at 12 h(p＜0.05),then slowly decreased till 48 h.After that increased gradually till 96 h(p＜0.05),but in group of 0.006 mg/l Cu²⁺ treatment the contents of MT got the highest points at 24 h(p＜0.05).When in 0.14,0.43 and 1.35 mg/l of Zn²⁺ treatment,MT contents got the highest points at 12 h(p＜0.05),and rapidly decreased. After 24 h,MT contents tended to be steady.However,when exposed in 0.5,1.6 and 5.0 mg/l of Cd²⁺ solution,variations of MT were similar to that in Zn²⁺ treatment,but MT contents got the highest points at 6 h(p＜0.05),then rapidly decreased till 12 h. Variations of MT contents in vivo after heavy metal ions treatments reflected that MT in C.simula might be considered as a biomarker to monitor heavy metals pollutants.Variations of MDA contents after the worms were exposed in Cu,Zn and Cd solutions at different concentrations for 96 h demonstrated that the contents of MDA distinctly changed at 6 h(p＜0.05) in all the treatment groups,except for in the 5.0 mg/l Cd²⁺ treatment.MDA contents in Cu²⁺ treatment groups were all higher than that of control groups.In 0.056 mg/l Cu²⁺ treatment,it quickly increased and reached the peak values at 6 h,then slowly decreased and tended to be steady,but in groups of 0.006 and 0.018 mg/l Cu²⁺ solutions peak values of MDA contents appeared at 72 h(p＜0.05).While in three concentrations of Zn²⁺ solutions,MDA contents all kept lower than control values(except for 0.43 mg/l Zn²⁺ treatment at 96 h),and rapidly decreased at 6 h(p＜0.05),then gradually increased.However,in groups of 0.5 and 1.6 mg/l Cd²⁺ treatments,the significant increase of MDA content appeared at 6 h(p＜0.05),then the values in all concentration treatments decreased to the nadir at 12 h(p＜0.05),and then gradually increased,but differently,in 5.0 mg/l Cd²⁺ treatment,it was near to control values at 48 h,and then slowly decreased.In group of 1.6 mg/l Cd²⁺ treatment,MDA content reached the second peak values at 48 h.Present data showed that three heavy metal ions could affect lipid peroxidation and MDA content in C.simula.And the variations of MDA content implied the toxicity of three heavy metal ions to C.simula,and mignt be used as a biomarker to monitor indirectly heavy metal pollution.