Study On Combined Toxicity Of Selenium And Mercury,Cadmium,Zinc

In recent years,selenium-enriched agricultural products have been more popular.Studies have shown that selenium-enriched foods have improved human antioxidant capacity,antagonize other heavy metallic toxicity,but the relationship between selenium content and strong metal ability is still unclear.And current research is mostly carried out in animals and plants or their exile cells,rarely involve molecular weight.In order to explore the toxic effects of Se on DNA,a plasmid DNA assay was used to quantitatively analyze the joint toxicity of mixed system.Based on single toxicity,this experiment designed binary,ternary and quaternary mixed systems and explored the law of toxicity change of the combined systems.The combined effects were evaluated by toxicity unit method,additive index method and mixed toxicity index method.The main conclusions of this study are as follows:（1）Through the plasmid DNA experiment of a single heavy metal sample,it is found that the four heavy metals have obvious concentration-effect relationship with plasmid DNA when they exist alone.TD₂₀values of Hg²⁺,Cd²⁺,Zn²⁺and Se⁴⁺on plasmid DNA are 0.026,0.911,1.009 and 0.116 mmol/L respectively,that is,the order of toxicity to DNA is Hg²⁺>Se⁴⁺>Cd²⁺>Zn²⁺.（2）Eight binary combinations were designed by the straight-line bisection ray method,and plasmid DNA experiments were carried out on binary heavy metal samples.The results showed that the S<1,AI>0 and MTI>1 of the binary combination system of Hg²⁺+Cd²⁺showed synergistic effect.And when the molar concentration ratio of Cd to Se is 1:1,the absolute value of AI is the largest,which means that the synergistic effect is the strongest.The binary combination system of Hg²⁺+Zn²⁺,Hg²⁺+Se⁴⁺,Zn²⁺+Se⁴⁺showed antagonism,which indicated that Zn²⁺,Se⁴⁺could antagonize the toxicity of Hg²⁺.The AI of Cd²⁺+Zn²⁺binary combination system is less than 0,which shows antagonism.When the molar concentration ratio of Zn to Cd is 6.7:1,the absolute value of AI is 8.01,which shows that the higher the content of Zn²⁺,the stronger the antagonism to Cd²⁺.The Cd²⁺+Se⁴⁺combination system is antagonistic when the molar concentration ratio of Cd²⁺to Se⁴⁺is 2.6:1,2.1:1,1.4:1and 0.9:1,and the absolute value of AI is 1.10 when the concentration ratio of Cd and Se is 2.1:1,which is the strongest antagonistic effect.When the molar concentration ratio of Cd²⁺and Se⁴⁺is 8.0:1,it shows that the higher the content of Se⁴⁺,the stronger the ability of antagonizing Cd²⁺,but when the concentration of Se⁴⁺is very low,it will produce synergistic toxicity.（3）Eight ternary mixed systems were designed by uniform design concentration ratio method,and plasmid DNA assay were carried out on ternary heavy metal samples.The AI of ternary heavy metal mixed systems was less than 0,showing antagonistic effect,which indicated that Zn²⁺and Se⁴⁺could antagonize the toxicity of Hg²⁺and Cd²⁺when they existed singly or simultaneously.TD₂₀value of ternary system of Hg²⁺+Zn²⁺+Se⁴⁺and Cd²⁺+Zn²⁺+Se⁴⁺are all greater than 1mmol/L,while that of ternary system of Hg²⁺+Cd²⁺+Zn²⁺and Hg²⁺+Cd²⁺+Se⁴⁺are all less than0.9mmol/L.It indicated that Zn²⁺and Se⁴⁺had stronger antagonistic ability when they existed at the same time.Compared with the toxicity 1:1:1 system,the absolute value of AI of mass concentration 1:1:1 system is larger and the antagonistic effect is stronger.（4）Five quaternary mixed systems were designed by uniform design concentration ratio method.Plasmid DNA assay were carried out on quaternary heavy metal samples.The AI<0 of quaternary heavy metal mixed systems was antagonistic,which indicated that Zn²⁺and Se⁴⁺could antagonize the synergistic toxicity of Hg²⁺and Cd²⁺.Multivariate analysis of variance showed that the effects of four main effects and their interactions on DNA damage rate reached a significant level（P<0.05）,which indicated that a single heavy metal with low toxicity also significantly affected the combined toxic effect of the mixed system on DNA.