Begeot M, Hemming F J, Aubert M L, Dubois P M
Laboratoire d'Histologie-Embryologie, CNRS UA 559, Oullins.
Ann Endocrinol (Paris). 1987;48(5):367-77.
Gonadotrophs were first detected at 18 days of gestation in normal rat fetus. Encephalectomy performed at 16 days of gestation did not modify the normal aspect of cells at term. In adenohypophysial primordia explanted from 13 days of gestation differentiated gonadotrophs were detected after culture (8 days) in medium containing insulin (minimal dose required: 0.5 microgram/ml) and transferrin (5 micrograms/ml). In contrast, in primordia explanted at 11 and 12 days of gestation, GnRH 10(-9) to 10(-12) M was required for the first 24 hours of culture to induce differentiation of cells which was obtained in synergy with insulin and transferrin. On the other hand, fetal hypothalamic GnRH and pituitary GnRH receptors were observed from 12 days of gestation which can explain the observations made on primordia explanted at 13 days. Lactotrophs first appeared at term in normal rat fetus. In vitro, differentiation of lactotrophs was not observed in primordia explanted from 13 days in the presence of insulin and transferrin alone, but it was induced by GnRH (10(-9) M) for the 24 hours of culture in the same medium. The action of GnRH was mediated through glycoproteins and specifically isolated alpha subunit. Indeed, purified LH alpha-subunit added in medium instead of GnRH induced differentiation of lactotrophs from 10(-9) M with an increase in the number of cells related to the dose of hormone. Differentiation of the two cell types is very linked in these culture conditions. Gonadotroph differentiation is regulated by an hypothalamic endocrine secretion whereas lactotroph differentiation is more dependent on a paracrine secretion.
在正常大鼠胎儿中，妊娠18天时首次检测到促性腺激素细胞。妊娠16天时进行脑切除术，足月时细胞外观未发生改变。从妊娠13天取出的腺垂体原基在含有胰岛素（所需最小剂量：0.5微克/毫升）和转铁蛋白（5微克/毫升）的培养基中培养（8天）后，检测到分化的促性腺激素细胞。相比之下，在妊娠11天和12天取出的原基中，培养的前24小时需要10⁻⁹至10⁻¹²M的促性腺激素释放激素（GnRH）来诱导细胞分化，这与胰岛素和转铁蛋白协同作用。另一方面，从妊娠12天开始观察到胎儿下丘脑GnRH和垂体GnRH受体，这可以解释在妊娠13天取出的原基上所做的观察结果。催乳激素细胞在正常大鼠胎儿足月时首次出现。在体外，仅在胰岛素和转铁蛋白存在的情况下，从妊娠13天取出的原基中未观察到催乳激素细胞的分化，但在相同培养基中培养24小时时，GnRH（10⁻⁹M）可诱导其分化。GnRH的作用是通过糖蛋白和特异性分离的α亚基介导的。事实上，在培养基中添加纯化的促黄体生成素α亚基代替GnRH，从10⁻⁹M开始诱导催乳激素细胞分化，细胞数量随激素剂量增加。在这些培养条件下，两种细胞类型的分化密切相关。促性腺激素细胞的分化受下丘脑内分泌分泌调节，而催乳激素细胞的分化更依赖旁分泌分泌。
