Urbatzka R, Lutz I, Opitz R, Kloas W
Department of Inland Fisheries, Leibniz-Institute of Freshwater Biology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
Gen Comp Endocrinol. 2006 Apr;146(2):119-25. doi: 10.1016/j.ygcen.2005.10.005. Epub 2005 Dec 5.
Environmental pollutants can interfere with the endocrine system of a variety of animals and are suggested to contribute to the worldwide decline of amphibians. In this study, the effects of endocrine disrupting compounds (EDC) on the hypothalamus-pituitary-gonad axis, regulating reproduction, were investigated in Xenopus laevis by determining their potential impact on gene expression of gonadotropin releasing hormone (GnRH), luteinizing hormone beta-subunit (LHbeta) and follicle-stimulating hormone beta-subunit (FSHbeta) in brain and pituitary using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). One environmental sample and four model compounds, ethinylestradiol (EE2), tamoxifen (TAM), methyldihydrotestosterone (MDHT), and flutamide (FLU), corresponding to (anti)estrogenic and (anti)androgenic modes of action were used at 10(-8)M during a four weeks exposure of adults of both sexes. In general, males had a higher LHbeta mRNA level compared to females, while the mRNA expression of FSHbeta and GnRH did not differ between both sexes. EE2 and MDHT treatment decreased LHbeta mRNA expression in the brain of male X. laevis, while only EE2 but not MDHT reduced LHbeta mRNA in females indicating classical negative feed-back mechanisms on hypophyseal gonadotropin expression. TAM increased LHbeta mRNA and FSHbeta mRNA expression in female X. laevis while none of the other treatments showed an effect on FSHbeta mRNA expression. GnRH expression was not changed by any treatment and exposure of X. laevis to Lambro river water had no significant effect on any of the genes examined. It is reported for the first time in amphibians that gonadotropin mRNA expression is differentially regulated by (anti)estrogenic and (anti)androgenic EDC and that gender-specific patterns of gene expression exist.
环境污染物会干扰多种动物的内分泌系统，并被认为是导致全球两栖动物数量减少的原因之一。在本研究中，通过使用半定量逆转录聚合酶链反应（RT-PCR）测定内分泌干扰化合物（EDC）对非洲爪蟾下丘脑-垂体-性腺轴（调节生殖）的影响，研究其对大脑和垂体中促性腺激素释放激素（GnRH）、促黄体生成素β亚基（LHβ）和促卵泡生成素β亚基（FSHβ）基因表达的潜在影响。使用一种环境样品和四种模型化合物，即乙炔雌二醇（EE2）、他莫昔芬（TAM）、甲基二氢睾酮（MDHT）和氟他胺（FLU），它们分别对应（抗）雌激素和（抗）雄激素作用模式，在为期四周的实验中，以10⁻⁸M的浓度对成年雌雄非洲爪蟾进行暴露处理。总体而言，雄性的LHβ mRNA水平高于雌性，而FSHβ和GnRH的mRNA表达在两性之间没有差异。EE2和MDHT处理降低了雄性非洲爪蟾大脑中LHβ mRNA的表达，而只有EE2而非MDHT降低了雌性的LHβ mRNA，这表明存在对垂体促性腺激素表达的经典负反馈机制。TAM增加了雌性非洲爪蟾中LHβ mRNA和FSHβ mRNA的表达，而其他处理均未对FSHβ mRNA表达产生影响。任何处理均未改变GnRH的表达，并且非洲爪蟾暴露于兰布罗河水中对所检测的任何基因均无显著影响。首次在两栖动物中报道促性腺激素mRNA表达受（抗）雌激素和（抗）雄激素EDC的差异调节，并且存在基因表达的性别特异性模式。
