Eagle R C, Tortonese D J
Department of Anatomy, University of Bristol, Bristol BS2 8EJ, England, United Kingdom.
Biol Reprod. 2000 Sep;63(3):826-32. doi: 10.1095/biolreprod63.3.826.
Little is known about the neuroendocrine control of fertility in the horse. In this species, unusual features characterize the normal estrous cycle such as a prolonged preovulatory LH surge during the follicular phase and a distinctive FSH surge during the midluteal phase. This study investigated the distribution and hormonal identity of gonadotrophs in the pars distalis (PD) and pars tuberalis (PT) of the equine pituitary gland as possible morphological bases for the referred unusual endocrine characteristics. In addition, the proportion of gonadotrophs in relation to other pituitary cell types during both the estrous cycle and anestrus were investigated. Pituitary glands were collected from sexually active (n = 5) and seasonally anestrous (n = 5) mares in November, and single or double immunofluorescent staining was carried out on 6-microm sections using monoclonal antibodies to the LHbeta or FSHbeta subunits and a polyclonal antibody to ovine LHbeta. Gonadotrophs were densely distributed around the pars intermedia in the PD and in the caudal ventral region of the PT. In addition to isolated cells, clusters of gonadotrophs were found surrounding the capillaries. No significant differences were detected in the number of gonadotrophs between sexually active and anestrous mares in either the PD or PT. In the PD, gonadotrophs represented 22.7 +/- 5. 8% and 19.1 +/- 2.1% of the total cell density in sexually active and anestrous animals, respectively (P: > 0.05). However, in the PT, gonadotrophs accounted for a higher proportion of the total cell population in sexually active (6 +/- 0.1%) than in anestrous (1.2 +/- 0.05%) mares (P: < 0.02). Double immunofluorescence revealed that the majority of gonadotrophs were bihormonal (i.e., positive for LH and FSH); however, in the sexually active mare, a larger proportion of gonadotrophs (22.5 +/- 3.6%) were monohormonal for either LH or FSH, when compared to anestrous animals (9.7 +/- 1.2%; P: < 0.02). Based on these findings we conclude that: 1) although the relative distribution of gonadotrophs is similar to those reported for other species, a significantly larger proportion of gonadotroph cells is present in the equine pituitary gland; 2) gonadotroph density does not appear to differ between sexually active and anestrous mares in the PD; 3) a larger proportion of gonadotrophs is apparent in the PT of sexually active animals; and 4) although a large incidence of bihormonal gonadotrophs is present in the horse, specific LH or FSH cells differentiate predominantly during the sexually active phase.
关于马生育能力的神经内分泌控制，人们了解甚少。在这个物种中，正常发情周期具有一些不寻常的特征，比如卵泡期促黄体生成素（LH）排卵前激增持续时间延长，以及黄体中期促卵泡生成素（FSH）有明显激增。本研究调查了马垂体远侧部（PD）和结节部（PT）中促性腺激素细胞的分布及激素特性，作为上述异常内分泌特征可能的形态学基础。此外，还研究了发情周期和乏情期促性腺激素细胞相对于其他垂体细胞类型的比例。11月从性活跃（n = 5）和季节性乏情（n = 5）的母马采集垂体，使用针对LHβ或FSHβ亚基的单克隆抗体以及针对绵羊LHβ的多克隆抗体，对6微米切片进行单重或双重免疫荧光染色。促性腺激素细胞密集分布于PD的中间部周围以及PT的尾侧腹侧区域。除了单个细胞外，还发现促性腺激素细胞簇围绕着毛细血管。在PD或PT中，性活跃母马和乏情母马的促性腺激素细胞数量未检测到显著差异。在PD中，促性腺激素细胞分别占性活跃和乏情动物总细胞密度的22.7±5.8%和19.1±2.1%（P：>0.05）。然而，在PT中，促性腺激素细胞在性活跃母马（6±0.1%）中占总细胞群体的比例高于乏情母马（1.2±0.05%）（P：<0.02）。双重免疫荧光显示，大多数促性腺激素细胞是双激素的（即对LH和FSH均呈阳性）；然而，与乏情动物相比，性活跃母马中更大比例的促性腺激素细胞（22.5±3.6%）对LH或FSH呈单激素性（9.7±1.2%；P：<0.02）。基于这些发现，我们得出以下结论：1）尽管促性腺激素细胞的相对分布与其他物种报道的相似，但马垂体中促性腺激素细胞的比例显著更大；2）PD中性活跃和乏情母马的促性腺激素细胞密度似乎没有差异；3）性活跃动物的PT中促性腺激素细胞比例更高；4）尽管马中双激素促性腺激素细胞的发生率很高，但特定的LH或FSH细胞主要在性活跃期分化。
