Regulation of pituitary function by pituitary hormones

垂体激素对垂体功能的调节

基本信息

批准号：
07454226
负责人：
KIKUYAMA Sakae
金额：
$ 4.99万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Hormonal messenger molecules are released from specific cells into the general circulation to reach distant target cells. However, the molecules can also be released to influence the function of neighboring cells as paracrine or autocrine system.In the bullfrog pituitary, PRL cells frequently located in contact with gonadotropin cells. It was found that PRL enhances the responsiveness of LH cells to GnRH in vitro. The responsiveness to GnRH became less conspicuous as the cell density was reduced. Addition of PRL to the medium enhanced the responsiveness to the secretagogue, and addition of antiserum against PRL lowered the responsiveness to a certain extent. Secondly, experiments were performed to study the effect of free alpha-subunit of glycoprotein hormones existing in the secretory granules of PRL.It was found that addition of alpha-subunit into the culture medium enhanced the release of PRL.On the other hand, we have found that a considerable number of cells exhibited secretion of … More both PRL and GH when the pituitaries were dispersed and cultured. This suggested that either transcription or translation of PRL and/or GH had been blocked until the cells were dispersed and cultured. Cycloheximide blocked the appearance of such cells. These findings indicated that the cells secreting both PRL and GH after dispersal and culture possessed the mRNAs for these hormones before they were transferred to an in vitro system. In addition, several of the PRL-immunoreactive cells possesses GHmRNA.Prolactin mRNA was also expressed in several of the GH immunoreactive cells.In conclusion, paracrine and autocrine regulation of pituitary cell function in amphibians were elucidated : (1) PRL acts directly on gonadotrophs to enhance their responsiveness to GnRH in a paracrine fashion. (2) Both translation of PRL mRNA in GH cells and translation of GH mRNA in PRL cells are triggered by cell dispersion and/or culture, suggesting the presence of paracrine factors that inhibit the translation of PRLmRNA in GH cells and of GHmRNA in PRL cells. (3) Alpha-subunit secreted by PRL cells acts as an autocrine and/or paracrine factor to enhance the release of PRL. Less

激素信使分子从特定细胞释放到全身循环中以到达远处的靶细胞。然而，这些分子也可以被释放以影响邻近细胞的功能，例如旁分泌或自分泌系统。在牛蛙垂体中，PRL细胞经常位于接触处。发现PRL在体外增强LH细胞对GnRH的反应性，随着细胞密度的降低，对GnRH的反应性变得不那么明显。其次，通过实验研究了PRL分泌颗粒中存在的糖蛋白激素游离α亚基的作用。发现在培养基中添加α亚基可增强PRL的释放。另一方面，我们发现当垂体处于关闭状态时，相当数量的细胞同时分泌PRL和GH。这表明，在细胞被分散和培养之前，PRL和/或GH的转录或翻译被阻断。这些发现表明，在分散和培养后，细胞分泌PRL和GH。在转移到体外系统之前，培养物中含有这些激素的 mRNA。此外，一些 PRL 免疫反应性细胞含有 GHmRNA。催乳素 mRNA 在一些细胞中也有表达。 GH 免疫反应性细胞。总之，阐明了两栖动物垂体细胞功能的旁分泌和自分泌调节：（1）PRL 直接作用于促性腺激素，以旁分泌方式增强其对 GnRH 的反应性（2）PRL mRNA 在 GH 细胞中的两种翻译。 PRL 细胞中 GH mRNA 的翻译是由细胞分散和/或培养触发的，表明在细胞中存在抑制 PRLmRNA 翻译的旁分泌因子。 (3) PRL 细胞分泌的 GH 亚基作为自分泌和/或旁分泌因子，增强 PRL 的释放。