Huhtaniemi I
Department of Physiology, University of Turku, Finland.
Reprod Fertil Dev. 1995;7(5):1025-35. doi: 10.1071/rd9951025.
The endocrine function of the mammalian pituitary-gonadal axis begins in utero. This is important particularly for the ontogeny and function of the male reproductive organs, the induction of which is critically dependent on the two fetal testicular hormones, testosterone and anti-müllerian hormone. In contrast, ovarian endocrine activity begins only after birth. The earliest phases of testicular hormone production are probably under autocrine or paracrine regulation, but the dependence on gonadotrophins starts in fetal life. During maturation of the hypothalamic-pituitary-testicular axis, the target organs acquire their responsiveness (viz receptors) before the onset of secretion of the tropic hormonal stimulus. The last link to develop is the feedback regulation, and the whole axis is functional in the developing male rat during the last days of gestation. Although gonadotrophin secretion starts in both sexes simultaneously, the fetal ovary is endocrinologically quiescent--its gonadotrophin responsiveness and endocrine activity begin only after birth. The fetal and postnatal periods of testicular activity have crucial effects on male sexual differentiation, whereas in the female, early sexual development occurs autonomously without influence of ovarian function. The purpose of this review is to elucidate some of the recent findings on the molecular mechanisms involved in the perinatal maturation of the rat hypothalamic-pituitary-gonadal axis.
哺乳动物垂体 - 性腺轴的内分泌功能始于子宫内。这对于雄性生殖器官的个体发育和功能尤为重要，雄性生殖器官的诱导关键依赖于两种胎儿睾丸激素，即睾酮和抗苗勒管激素。相比之下，卵巢内分泌活动仅在出生后才开始。睾丸激素产生的最早阶段可能受自分泌或旁分泌调节，但对促性腺激素的依赖始于胎儿期。在下丘脑 - 垂体 - 睾丸轴成熟过程中，靶器官在促性腺激素刺激分泌开始之前就获得了它们的反应能力（即受体）。最后形成的环节是反馈调节，在妊娠最后几天，整个轴在发育中的雄性大鼠体内发挥功能。尽管促性腺激素分泌在两性中同时开始，但胎儿卵巢在内分泌方面处于静止状态——其对促性腺激素的反应能力和内分泌活动仅在出生后才开始。睾丸活动的胎儿期和出生后时期对雄性性别分化有至关重要的影响，而在雌性中，早期性发育是自主发生的，不受卵巢功能影响。本综述的目的是阐明一些关于大鼠下丘脑 - 垂体 - 性腺轴围产期成熟所涉及分子机制的最新研究发现。
