Hu L, Lawson D M
Department of Physiology, Wayne State University, School of Medicine, Detroit, Michigan 48201, USA.
J Endocrinol. 1996 Jan;148(1):113-20. doi: 10.1677/joe.0.1480113.
In this study we examined the effects of dopamine (DA) and its withdrawal on in vitro prolactin (PRL) release from subpopulations of lactotrophs from two regions of the anterior pituitary obtained from untreated ovariectomized (OVX) rats or OVX rats treated with estrogen, progesterone or a combination of the two. Anterior pituitaries were cut horizontally into an inner (dorsal) zone and an outer (ventral) zone. Each of these regions was enzymatically dispersed and the resulting cells were otherwise untreated (unseparated) or centrifuged through a discontinuous Percoll gradient to separate the cells into two subpopulations (light and heavy cells). Each of these types of cells was perifused for 1 h with culture medium containing 1 microM DA followed by medium devoid of DA for 1 h. Prolactin released into the perifusion medium, collected as 5-min fractions, was measured by radioimmunoassay and normalized to the number of lactotrophs in the cellular pools as determined by immunocytochemistry. In the presence of DA, PRL release from unseparated cells of the outer zone was significantly increased by estradiol treatment compared with the release from similar cells from OVX rats. (Differences were considered significant where P < 0.05.) However, no effect of estradiol treatment was observed with unseparated cells of the inner zone or light or heavy cells from either zone. Progesterone had no effect on any cell type when administered alone. However, when progesterone was given following estradiol, PRL release from unseparated cells of the inner zone was increased significantly compared with similar cells from the other steroid-treated groups. Similar significant increases were observed with light and heavy cells of the outer zone, but there was no effect of the combined steroid treatment on light or heavy cells from the inner zone. When DA was withdrawn, prolactin release was significantly increased from all cells except unseparated cells of the outer zone of OVX rat pituitaries. However, when the cells of the outer zone from OVX rats were separated into light and heavy cells, they responded to the withdrawal of DA with significant and equivalent increases in prolactin release. Light cells of the inner zone of pituitaries from OVX rats were more responsive to DA withdrawal than were heavy cells. Estradiol increased the response to the withdrawal of DA by light and heavy cells of the outer zone and heavy cells of the inner zone. Progesterone significantly reversed these effects of estradiol on separated cells. These results suggest that lactotrophs in two regions of rat pituitaries respond differently to dopamine and to its withdrawal, that subpopulations of lactotrophs within these regions also respond differently and that steroids modulate these responses.
在本研究中，我们检测了多巴胺（DA）及其撤除对来自未处理的去卵巢（OVX）大鼠或经雌激素、孕激素或二者联合处理的OVX大鼠垂体前叶两个区域的不同亚群催乳素细胞体外催乳素（PRL）释放的影响。垂体前叶被水平切成一个内侧（背侧）区和一个外侧（腹侧）区。将每个区域进行酶解分散，所得细胞不做处理（未分离）或通过不连续的Percoll梯度离心，将细胞分离成两个亚群（轻细胞和重细胞）。将每种类型的细胞用含1 μM DA的培养基灌流1小时，随后用不含DA的培养基灌流1小时。收集灌流培养基中5分钟间隔的样品，用放射免疫分析法测定释放的催乳素，并根据免疫细胞化学法测定的细胞库中催乳素细胞的数量进行标准化。在DA存在的情况下，与来自OVX大鼠的相似细胞相比，雌二醇处理显著增加了外侧区未分离细胞的PRL释放。（P < 0.05时差异被认为具有显著性。）然而，在内侧区未分离细胞或两个区域的轻细胞或重细胞中未观察到雌二醇处理的影响。单独给予孕激素对任何细胞类型均无影响。然而，当在雌二醇之后给予孕激素时，与其他类固醇处理组的相似细胞相比，内侧区未分离细胞的PRL释放显著增加。在外侧区的轻细胞和重细胞中也观察到类似的显著增加，但类固醇联合处理对内侧区的轻细胞或重细胞没有影响。当撤除DA时，除OVX大鼠垂体外侧区未分离细胞外，所有细胞的催乳素释放均显著增加。然而，当将OVX大鼠外侧区的细胞分离成轻细胞和重细胞时，它们对DA撤除的反应是催乳素释放显著且等量增加。OVX大鼠垂体内侧区的轻细胞对DA撤除的反应比重细胞更敏感。雌二醇增加了外侧区轻细胞和重细胞以及内侧区重细胞对DA撤除的反应。孕激素显著逆转了雌二醇对分离细胞的这些作用。这些结果表明，大鼠垂体两个区域的催乳素细胞对多巴胺及其撤除的反应不同，这些区域内催乳素细胞的亚群反应也不同，并且类固醇调节这些反应。
