Huang Y S, Rousseau K, Sbaihi M, Le Belle N, Schmitz M, Dufour S
Laboratoire de Physiologie Générale et Comparée, Muséum National d'Histoire Naturelle, URA 90, Centre National de la Recherche Scientifique, Paris, France.
Endocrinology. 1999 Mar;140(3):1228-35. doi: 10.1210/endo.140.3.6598.
It has been suggested that in mammals, glucocorticoids, beside their stress-related inhibitory effects on reproductive function, may also play a stimulatory role at the onset of puberty. Using the juvenile female eel as a model, we investigated the potential stimulatory role of cortisol (F) on pituitary gonadotropin (GtH-II). GtH-II levels were measured by RIA, and messenger RNA (mRNA) levels for alpha- and GtH-II beta-subunits were determined by dot blot using homologous probes. F treatment increased eel pituitary GtH-II content in vivo and in vitro. Using a long term, serum-free primary culture of pituitary cells, we studied the direct effect of F on GtH-II production. F increased the GtH-II cellular content in vitro in a dose- and time-dependent manner. The relative potencies of various corticosteroids on GtH-II were: triamcinolone acetonide > dexamethasone > F >> cortisone and aldosterone, indicating a glucocorticoid-specific receptor (GR). F stimulated GtH-II production through a selective increase in mRNA levels for GtH-II beta-subunit; no significant effect was observed on alpha-subunit mRNA levels. This stimulatory effect of F on GtH-II beta, played out directly at the pituitary cell level, recalls that of F on FSHbeta in the rat. The present study, performed in a primitive teleost at the juvenile stage, suggests that the role of F in the positive regulation of gonadotropins at puberty may have arisen early in vertebrate evolution.
有人提出，在哺乳动物中，糖皮质激素除了对生殖功能有与应激相关的抑制作用外，在青春期开始时可能也发挥刺激作用。我们以幼年雌性鳗鱼为模型，研究了皮质醇（F）对垂体促性腺激素（GtH-II）的潜在刺激作用。通过放射免疫分析法测定GtH-II水平，使用同源探针通过斑点印迹法测定α-亚基和GtH-IIβ-亚基的信使核糖核酸（mRNA）水平。F处理在体内和体外均增加了鳗鱼垂体GtH-II含量。我们使用垂体细胞的长期无血清原代培养，研究了F对GtH-II产生的直接影响。F在体外以剂量和时间依赖性方式增加了GtH-II细胞含量。各种皮质类固醇对GtH-II的相对效力为：曲安奈德>地塞米松>F>>可的松和醛固酮，表明存在糖皮质激素特异性受体（GR）。F通过选择性增加GtH-IIβ-亚基的mRNA水平来刺激GtH-II的产生；对α-亚基mRNA水平未观察到显著影响。F对GtH-IIβ的这种刺激作用在垂体细胞水平直接发挥，让人联想到F对大鼠卵泡刺激素β（FSHβ）的作用。本研究在幼年阶段的一种原始硬骨鱼中进行，表明F在青春期对促性腺激素的正向调节中的作用可能在脊椎动物进化早期就已出现。
