Urbatzka Ralph, Lorenz Claudia, Wiedemann Caterina, Lutz Ilka, Kloas Werner
CIIMAR, Centre of Marine and Environmental Research, Laboratory of Ecotoxicology, Genomics and Evolution, Rua dos Bragas 289, 4050-123 Porto, Portugal.
Department of Ecophysiology and Aquaculture, Leibniz-Institute for Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
Comp Biochem Physiol C Toxicol Pharmacol. 2014 Mar;160:1-8. doi: 10.1016/j.cbpc.2013.11.003. Epub 2013 Nov 13.
Steroids are known to influence the reproductive pituitary-gonadal axis in adult amphibians. Here, we studied the effects of hormones on pituitary and gonadal mRNA expression during the development of Xenopus laevis. Tadpoles at NF 58 (prometamorphosis) and at NF 66 (freshly metamorphosed) were exposed for three days to 17β-estradiol (E2), tamoxifen (TAM), testosterone (T), dihydrotestosterone (DHT) at 10(-7)M, and flutamide (FLU) at 10(-6)M. In both genders at NF 58 and 66, T and DHT decreased luteinizing hormone beta (lhβ), but increased follicle stimulating hormone beta (fshβ), while FLU induced lhβ specifically in males. In the testis steroidogenic genes (p450 side chain cleavage enzyme, p450scc; steroid acute regulatory protein, star) at NF 58 showed a similar pattern as for lhβ, while the response at NF 66 was only partially present. In females, TAM induced lhβ at NF 58, while E2 decreased lhβ and increased fshβ at NF 66. In the ovaries, no alterations were observed for the steroidogenic genes. Summarizing, gonadotropic and steroidogenic mRNA expression may indicate control of androgen level during testis differentiation in male tadpoles at NF 58. In females the non-responsiveness of steroidogenic genes could be a sign of gonadal quiescence during pre-pubertal stages.
已知类固醇会影响成年两栖动物的生殖垂体 - 性腺轴。在此，我们研究了激素对非洲爪蟾发育过程中垂体和性腺mRNA表达的影响。处于NF 58（前变态期）和NF 66（刚变态完成）的蝌蚪分别暴露于10⁻⁷M的17β - 雌二醇（E2）、他莫昔芬（TAM）、睾酮（T）、双氢睾酮（DHT）以及10⁻⁶M的氟他胺（FLU）中三天。在NF 58和66阶段的两性中，T和DHT降低了促黄体生成素β（lhβ），但增加了促卵泡生成素β（fshβ），而FLU仅在雄性中诱导lhβ。在NF 58阶段，睾丸中的类固醇生成基因（细胞色素P450侧链裂解酶，p450scc；类固醇急性调节蛋白，star）表现出与lhβ相似的模式，而在NF 66阶段的反应仅部分存在。在雌性中，TAM在NF 58阶段诱导lhβ，而E2在NF 66阶段降低lhβ并增加fshβ。在卵巢中，未观察到类固醇生成基因有变化。综上所述，促性腺激素和类固醇生成mRNA表达可能表明在NF 58阶段雄性蝌蚪睾丸分化过程中雄激素水平受到控制。在雌性中，类固醇生成基因无反应可能是青春期前性腺静止的一个标志。
