Abstract：To demonstrate the estrogenic activities of glyphosate and clarify the underlying molecular mechanism, 1~3days old Japanese medaka were exposed to 0.2, 2, 20, 200, 2000μg/L of glyphosate for 5weeks. Transcription levels of vitellogenin (VTG I) and enzyme genes involved in 17β-E2biosynthesis and metabolism were measured by Q-RT-PCR. While glyphosate markedly up-regulated VTG transcription levels in both female and male fish, the upward trend was inhibited at the high glyphosate concentrations (at 200μg/L and 2000μg/L for female, at 2000μg/L for male). The gender specific molecular mechanism was observed. In female fish, VTG induction would be due to the increase of transcription levels of FSH gene in brain and CYP19A gene in the gonad, and therefore enhancing the biosynthesis of 17β-E2. However in male fish, the inhibited CYP1A, CYP1B and CYP3A transcription levels which would inhibit 17β-E2metabolism would be the reasonable explanation.
