González Miriam, Reyes Ricardo, Damas Carmen, Alonso Rafael, Bello Aixa R
Cell Biology Section, University of La Laguna School of Biology and FICIC, 38230 La Laguna, Tenerife, Spain.
Gen Comp Endocrinol. 2008 Feb 1;155(3):857-68. doi: 10.1016/j.ygcen.2007.10.007. Epub 2007 Nov 6.
Estradiol is a critical factor in the anterior pituitary secretory activity of mammalian females. Previous reports have demonstrated the presence of oestrogen receptor alpha (ERalpha) and beta (ERbeta) in specific anterior pituitary cells from ovariectomized rats, as well as in the whole anterior pituitary at particular stages of the rat oestrous cycle. However, the ERalpha and ERbeta distribution patterns in specific hormone producing cells of the anterior pituitary during the oestrous cycle remain to be clarified. The purpose of this study was to determine the cellular and subcellular distribution of both ER-subtypes during the rat oestrous cycle, using immunochemistry at light- and electron-microscope levels. ERalpha-immunoreactive (ir) cells mainly corresponded to PRL-ir cells and, to a lesser extent, to TSH-, FSH- and GH-ir cells. ERbeta-ir cells corresponded to a few GH-, PRL- and FSH-ir cells, whichever the phase of the cycle. ERalpha-ir was found either in the cytoplasm and/or the nucleus, depending on the phase of the oestrous cycle, while ERbeta-ir was always detected in the cytoplasm. Both ER-subtypes were immunoreactives inside the rough endoplasmic reticulum (RER), secretory vesicles (SV) and free in the cytosol. The highest number of ERalpha-ir cells was consistently found at pro-oestrus midday and the lowest at metaoestrous, while the number of ERbeta-ir cells was low in all stages of the cycle. These results indicate that the genomic actions of oestrogen in the anterior pituitary cells during the oestrous cycle are mediated by ERalpha. However, the localization of ERalpha and ERbeta in the RER and SV suggest a different translational and/or post-translational pathway, which could be involved in non-genomic mechanisms.
雌二醇是哺乳动物雌性动物垂体前叶分泌活动的关键因素。先前的报道已证明，在去卵巢大鼠的特定垂体前叶细胞中以及在大鼠发情周期的特定阶段的整个垂体前叶中存在雌激素受体α（ERα）和β（ERβ）。然而，发情周期中垂体前叶特定激素产生细胞中的ERα和ERβ分布模式仍有待阐明。本研究的目的是利用光镜和电镜水平的免疫化学方法，确定大鼠发情周期中两种ER亚型的细胞和亚细胞分布。ERα免疫反应性（ir）细胞主要对应于PRL-ir细胞，在较小程度上对应于TSH-、FSH-和GH-ir细胞。无论发情周期处于哪个阶段，ERβ-ir细胞都对应于少数GH-、PRL-和FSH-ir细胞。根据发情周期的阶段，ERα-ir可在细胞质和/或细胞核中发现，而ERβ-ir始终在细胞质中检测到。两种ER亚型在粗面内质网（RER）、分泌囊泡（SV）内以及细胞质中均有免疫反应性。始终在发情前期中午发现ERα-ir细胞数量最多，在发情后期数量最少，而ERβ-ir细胞数量在周期的所有阶段都很低。这些结果表明，发情周期中雌激素在垂体前叶细胞中的基因组作用是由ERα介导的。然而，ERα和ERβ在RER和SV中的定位表明存在不同的翻译和/或翻译后途径，这可能参与非基因组机制。
