Mixture Toxicity Of Mercury,Cadmium,Lead And Arsenic In Early Embryo Development Of Zebrafish(Danio Rerio) And Marker Genes Screening

Emission of heavy metals in environment has been increased dramatically along with the rapid industrialization and urbanization in the many regions of the world.The association of numerous adverse effects on human and animals with heavy metals exposure has been reported,particularly the mass methylmercury poisioning in Iraq awaken the public conscious.Nowdays the most researchers focus their interests on elucidating toxic effects and mechanisms related to individuals of heavy metals exposure.However peoples most often interact with a mixture of heavy metal compounds in the environment.Thus it is urgent need to assess the toxic effects of mixture.In this study,I selected mercury,cadmium,lead and arsenic,which are well-known most toxic metals as subjects,and assessed the toxic effects of individuals and mixture by exposure zebrafish embryos to heavy metals from 4 to 120 hpf(hours post fertilization).On the basis of our previous studies,quantitative polymerase chain reaction(q PCR)was employed to determine and validate the genes responses to individuals and mixtures exposure.The main conclusions are as follows:(1)Assessing toxic effects association with individuals and mixtures exposure.Reliance on assessing the endpoints such as coagulated embryos,lack of somite formation,non-detachment of the tail and lack of heartbeat,I determined the half lethality concentrations of mercury,cadmium,lead,arsenic and mixtures.In addition,developmental toxicity was observed in exposure zebrafish embryos to these heavy metals.(2)Validating the genes response to individuals and mixtures of heavy metals.Based on our previous studies,forty one genes including 7,16,8,4 and 17 genes(including duplicated genes)regulated by mercury,cadmium,lead,arsenic and mixture were selected and validated by q PCR.Finally,24 genes were determined as candidates for further study.(3)Investigating the candidates responses to exposure concentrations and duration.Increase in relative expression of candidate genes was observed with exposure concentrations and durations depended manner under the certain exposure condition.Obvious differences in gene expression were observed in individuals and mixtures of heavy metals exposure.Taken together,reliance on assessing the toxic effects associated with exposure zebrafish embryos to mercury,cadmium,lead,arsenic and mixtures,I determined the toxic effects,half lethality concentrations and validated 24 genes as the potentials biomarkers for assessing the toxic effects related to individuals and mixtures,laid a foundation for further evaluating the effectiveness of these genes and revealed the toxicity mechanism.