Study On Combined Effects Of Pesticides Contamination On Endocrine Disrupting In Zebrafish

Endocrine disrupting pesticides are common exist in the environment,and can cause great harm to humans and wildlife.Current studies on endocrine disruptors have caused the attention of scientists around the world.And endocrine disrupting pesticides in the environment do not exist in the form of monomer,and most are in the form of the mixture.While traditional risk assessment that only focus on the single toxicity effect of contaminants and ignore the practice of joint toxicity effect,may underestimate the environmental risk of endocrine disruptors and potential threats.So joint endocrine effects of mixed pesticides to organism are very urgent and necessary.In the current study,the combined effects of several pesticides?malathion,fenitrothion,cypermethrin,prochloraz,bifenthrin and acetochlor?which are widely used in agricultural products at current,and can detect in the water ecological system were studied on the acute toxicity test under lethal doses by using the zebrafish as a model organism.On this basis,estrogen endocrine effect and thyroid endocrine disrupting effect of the binary mixed pesticides under low dose exposure to zebrafish different life stages were studied for the specific biomarkers of zebrafish endocrine disruptors by adopting the means of molecular biology.These results can provide a certain basis on mixed pesticide pollution of zebrafish risk assessment,as well as provide a certain amount of pesticide toxicology basis on the limited standards.The main conclusions are as follows:The single and joint acute toxicity test of four kinds of pesticides on zebrafish larvae showed that the 96 h-LC₅₀ values of cypermethrin,malathion,fenitrothion and prochloraz were 0.12,17.88,12.39and 1.45mg/L,respectively.According to pesticide toxicity ratio of the 96 h-LC_50,binary mixtures?cypermethrin+malathion,fenitrothion+cypermethrin,cypermethrin+prochloraz and fenitrothion+prochloraz?showed synergistic effect on zebrafish larvae in 24,48,72 and 96 h.Malathion+fenitrothion showed a synergistic effect in 24 h,but an additive effect in 48,72 and 96 h.The combined of malathion+prochloraz showed antagonism.All ternary or quaternary mixtures of pesticides showed synergistic effect on zebrafish larvae.Based on the acute toxicity test,estrogen endocrine effectsof genes of hypothalamu-pituitary-gonadal axis were investiged after exposure to the single and joint of bifenthrin,malathion and prochloraz at sublethal doses on zebrafish embryos.Cypermethrin and malathion had estrogenic effect on zebrafish embryos at certain concentrations,and could significantly induced estrogen receptors and aromatase gene expression.A certain time and acertain dose,exposure to binary mixtures of cypermethrin+malathion and malathion+prochloraz could significantly enhance the estrogenic effect,and could significantly alter ERa,ER?1,ER?2,CYP19b and CYP19a gene expression.The single and joint of the malathion and cypermethrin were also studied on endocrine disrupting effects of estrogen after male adult zebrafish were exposed for 21d in this paper.The results showed that the exposed groups could not damage the liver and gonad of male zebrafish.Exposure to cypermethrin?0.1?g/L?,all of malathion and binary mixture of cypermethrin+malathion,VTG and E2 in male zebrafish were increased compared to the control group,suggesting that estrogen effect was increase.At genes of the expression level,exposure to 1?g/L cypermethrin+250?g/L malathion on male zebrafish for 21d,vtg1 gene were significantly induced,showed that 1?g/L cypermethrin+250?g/L malathion may induce significantly estrogenic effect compared to the combined exposure group.The thyroid endocrine disrupting effects of the single and joint of bifenthrin and acetochlor on zebrafish embryos were studied.The bifenthrin and acetochlor on the zebrafish embryos showed that the72 h-LC₅₀ and 96 h-LC₅₀ of bifenthrin on zebrafish embryos were 0.50 and 0.34 mg/L,respectively.The72 h-LC₅₀ and 96 h-LC₅₀ of acetochlor on zebrafish embryos were 4.78 and 4.56 mg/L,respectively.According to pesticide toxicity ratio?1:1?of the 96 h-LC_50,binary mixture of bifenthrin+acetochlor showed antagonisc effect.Based on the acute toxicity test,according to the single pesticide 96 h-LC₅₀,thyroid endocrine disrupting effects were studied after zebrafish embryos were exposed to the single and joint of bifenthrin and acetochlor at sublethal doses for 14 d.The test results showed that the single and joint of bifenthrin and acetochlor could affect the oxidative stress and damage antioxidant system on zebrafish.The single and joint of bifenthrin and acetochlor could also significantly alter thyroid hormone levels?T3 and T4?.The binary of bifenthrin and acetochlor could strengthen thyroid endocrine disrupting effects on zebrafish compared to the simple pesticides.At the same time,binary mixture of 3?g/L bifenthrin+10?g/L acetochlor could significantly change the thyroid hormone genes expression of the HPG axis.Binary mixture of 3?g/L bifenthrin+10?g/L acetochlor could significantly enhance the effect of thyroid endocrine disturbance via combining with thyroid receptor TR?,and significantly induced by CRH and Tshb gene expression compared to the simple pesticides.