Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, IGB, Mueggelseedamm 301, 12587 Berlin, Germany.
Gen Comp Endocrinol. 2010 Sep 1;168(2):239-44. doi: 10.1016/j.ygcen.2010.02.012. Epub 2010 Feb 18.
The gonadotropins, luteinising hormone (LH) and follicle stimulating hormone (FSH), are important hormones regulating reproductive biology in vertebrates, especially the processes of steroidogenesis and gamete maturation. Despite the role of gonadotropins during the reproductive cycle in amphibians is well established, much less is known about the functional maturation of the hypothalamus-pituitary-gonad axis during larval development. Therefore, the present study aimed to analyze the expression profiles of hypophyseal LHbeta and FSHbeta mRNA and of their corresponding gonadal receptors (LH-R, FSH-R) in Xenopus laevis tadpoles during their ontogeny and sexual differentiation. The first significant elevation of LHbeta and FSHbeta mRNA was observed at late premetamorphosis. A clear raise of LHbeta mRNA was present during prometamorphic stages especially in males, while the LH-R only slowly increased during ontogeny with highest levels during metamorphic climax. In contrast, FSHbeta mRNA expression only slightly increased during ontogeny, however in both sexes the FSH-R mRNA was considerably elevated at prometamorphosis and further at metamorphic climax. Our results suggest that LHbeta and LH-R mRNA expression might be involved in initial maturation events of gametes, at least in males, while the gradually increase of FSH-R mRNA coincided with the advancing process of gamete maturation in both sexes. The present study provides for the first time evidence based on expression of gonadotropins and their corresponding gonadal receptors that the hypothalamus-pituitary-gonad axis evolves already at early stages of ontogeny and sexual differentiation in amphibians.
促性腺激素，黄体生成素（LH）和卵泡刺激素（FSH），是调节脊椎动物生殖生物学的重要激素，尤其是甾体生成和配子成熟过程。尽管在两栖动物的生殖周期中促性腺激素的作用已得到很好的证实，但对于下丘脑-垂体-性腺轴在幼虫发育过程中的功能成熟却知之甚少。因此，本研究旨在分析非洲爪蟾幼虫发育过程中脑下垂体 LHbeta 和 FSHbeta mRNA 及其相应的性腺受体（LH-R，FSH-R）的表达谱及其在性分化过程中的功能成熟。在后期的预变态期观察到 LHbeta 和 FSHbeta mRNA 的首次显著升高。在预变态阶段尤其是雄性中存在明显的 LHbeta mRNA 升高，而 LH-R 在发育过程中仅缓慢增加，在变态高峰期达到最高水平。相比之下，FSHbeta mRNA 的表达在发育过程中仅略有增加，但在两性中，FSH-R mRNA 在预变态期和进一步在变态高峰期都有显著升高。我们的结果表明，LHbeta 和 LH-R mRNA 的表达可能参与了配子的初始成熟事件，至少在雄性中是这样，而 FSH-R mRNA 的逐渐增加与两性配子成熟的进展过程相吻合。本研究首次提供了基于促性腺激素及其相应性腺受体表达的证据，表明在两栖动物的早期发育和性分化阶段，下丘脑-垂体-性腺轴已经进化。
