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Negative feedback mechanism on LH- and FSH-mRNA expression of selected ED in Xenopus.

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 luteinizing hormone β-subunit (LHβ) and follicle-stimulating hormone β-subunit (FSHβ) in brain and pituitary using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR).

Lambro river water and four model compounds, ethinylestradiol (EE2), tamoxifen (TAM), methyldihydrotestosterone (MDHT), 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. EE2 and MDHT treatment decreased LHβ mRNA expression in the brain of male X. laevis, while only EE2 but not MDHT reduced LHβ mRNA in females indicating classical negative feed-back mechanisms on hypophyseal gonadotropin expression. TAM increased LHβ mRNA and FSHβ mRNA expression in female X. laevis while none of the other treatments showed an effect on FSHβ mRNA expression. 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 indicating disturbance of reproductive processes at higher regulatory centres.

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Institute of Freshwater Ecology and Inland Fisheries
Mueggelseedamm 310
12587 BERLIN
Germany
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