The Estrogenic Activities Of Glyphosate In Medaka Fish And Analysis Of The Molecular Mechanism

In order to provide systematic experimental data and research the mode of action (MOA)of organophosphorus deeply, the hypothalamic-pituitary-gonadal-liver axis (HPGL axis)quantitative real-time PCR detection system of medaka fish was established in this study.Using this system, the estrogenic acitivity and MOA of glyphosate were further evaluated.The detail results are as follows：1. According to the gene expression profiles of HPGL axis pathways in male medakaexposed to glyphosate, Vtg1and Vtg2, biomarker for estrogenic activities in fish,transcription levels were significantly up-regulated when the concentrations of Glyphosate at2μg/L,20ug/L,200μg/L. CYP17mRNA relative expression levels were suppressed at2μg/L,20μg/L and200μg/L significantly. At0.2μg/L and2000μg/L concentrations,17β-HSDIexpression increased significantly. In all concentrations, estrogen metabolizing enzymes weresignificantly suppressed, except CYP1A and CYP1B at0.2μg/L concentration.2. According to the gene expression profiles of HPGL axis pathways in female medakaexposed to glyphosate, female Vtg1, Vtg2and CHGL transcription levels were significantlyinduced when the concertration of Glyphosate at0.2μg/L,2μg/L,20ug/L. And the inductionwas recovered with the raise of Glyphosate concertrations, showing a dose-responserelationship. The transcription levels of mdGnRH, FSHβ, FSHR and CYP19A were allsignificantly induced at0.2μg/L concentration. At low concentrations of glyphosate, thechanges of CYP17gene expression were not significant, but with the concentration increasing,CYP17gene expression were inhibited significantly at20μg/L,200μg/L,2000μg/Lconcentration. In all concentrations, estrogen metabolizing enzymes were significantlysuppressed.Therefore, glyphosate was an environmental estrogen, and could induce the biomarkerfor estrogenic activities in fish. The gender-specific MOA for the estrogenic activity ofglyphosate was observed:In male medaka fish, the induction on the VTG gene expressions were mostly due to thefact that glyphosate significantly inhibited the transcription levels of CYP17and estrogenmetabolizing enzyme genes (CYP1A, CYP1B and CYP3A), which were involved in androgenic synthesis and estrogenic metabolisms, respectively.In female medaka fish, reasons for the induction on the VTG and CHGL geneexpressions were that glyphosate significantly inhibited the transcription levels of CYP17,estrogen metabolizing enzyme gene (CYP1A, CYP1B and CYP3A), and significantly inducedthe mdGnRH gene, which leaded to the increase of FSH levels and consequently promotingthe synthesis of estrogen.