Fan X, Childs G V
Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77555, USA.
Endocrinology. 1995 May;136(5):2284-93. doi: 10.1210/endo.136.5.7720677.
Evidence has shown that epidermal growth factor (EGF), transforming growth factor-alpha (TGF alpha) and their receptors (EGF receptors) are present in the anterior pituitary, indicating that the growth factors are synthesized in situ and act locally. Studies have demonstrated that EGF could stimulate the hypothalamus-pituitary-adrenal (HPA) cortex axis, particularly at the pituitary level in vivo and in vitro, and also stimulate TGF alpha messenger RNA (mRNA) expression in cultured bovine pituitary cells. Recently, our studies have demonstrated that some stresses up-regulated EGF mRNA expression in the anterior pituitary, as detected by ribonuclease protection assay, further indicating the possible roles of EGF in the stress response. However, little is yet known about the sources and targets (sites of EGF receptors) of the growth factors in the pituitary. Therefore, this study was designed to localize EGF and TGF alpha mRNA and their receptors as well as to assess the effects of cold stress (CS) on their expression in the subsets of pituitary cells. In situ hybridization immunocytochemistry coupled with immunocytochemistry and dual immunocytochemistry studies revealed the presence of 1) EGF mRNA in somatotropes and gonadotropes; 2) TGF alpha mRNA in somatotropes, gonadotropes, and lactotropes; and 3) EGF receptors in all subsets of pituitary cells. CS (30 min) induced the expression of EGF mRNA in corticotropes and thyrotropes. EGF expression was not altered in somatotropes and gonadotropes. No significant changes were detected in TGF alpha mRNA expression in the pituitary cells after 30 min of CS. Expression of EGF receptors was also increased after 30 min of CS. This resulted from increases in EGF receptor-labeled cells among thyrotropes and gonadotropes. The cold stress-induced expression of EGF mRNA in corticotropes and thyrotropes fits with their overall activation after this type of stress. The increase in EGF receptor-labeled cells among thyrotropes may point to an important autocrine role for EGF in maintaining TSH responses to cold. On the other hand, the significance of EGF receptor up-regulation in gonadotropes (FSH-containing cells) caused by CS remains unknown.
有证据表明，表皮生长因子（EGF）、转化生长因子-α（TGFα）及其受体（EGF受体）存在于垂体前叶，这表明这些生长因子是在原位合成并在局部发挥作用。研究表明，EGF可刺激下丘脑-垂体-肾上腺（HPA）皮质轴，尤其是在体内和体外的垂体水平，还可刺激培养的牛垂体细胞中TGFα信使核糖核酸（mRNA）的表达。最近，我们的研究表明，通过核糖核酸酶保护试验检测到，一些应激会使垂体前叶中EGF mRNA的表达上调，这进一步表明EGF在应激反应中可能发挥的作用。然而，关于垂体中这些生长因子的来源和靶点（EGF受体的位点），目前所知甚少。因此，本研究旨在定位EGF和TGFα mRNA及其受体，并评估冷应激（CS）对垂体细胞亚群中它们表达的影响。原位杂交免疫细胞化学结合免疫细胞化学和双重免疫细胞化学研究显示：1）生长激素细胞和促性腺激素细胞中存在EGF mRNA；2）生长激素细胞、促性腺激素细胞和催乳激素细胞中存在TGFα mRNA；3）垂体细胞的所有亚群中都存在EGF受体。CS（30分钟）诱导促肾上腺皮质激素细胞和促甲状腺激素细胞中EGF mRNA的表达。生长激素细胞和促性腺激素细胞中EGF的表达未发生改变。CS 30分钟后，垂体细胞中TGFα mRNA的表达未检测到显著变化。CS 30分钟后，EGF受体的表达也增加了。这是由于促甲状腺激素细胞和促性腺激素细胞中EGF受体标记细胞的增加所致。冷应激诱导促肾上腺皮质激素细胞和促甲状腺激素细胞中EGF mRNA的表达，这与这类应激后它们的整体激活情况相符。促甲状腺激素细胞中EGF受体标记细胞的增加可能表明EGF在维持促甲状腺激素对寒冷的反应中具有重要的自分泌作用。另一方面，CS导致促性腺激素细胞（含促卵泡激素细胞）中EGF受体上调的意义尚不清楚。
