Mertani H C, Waters M J, Jambou R, Gossard F, Morel G
CNRS URA 1454, Faculty of Medicine, University Lyon-I, Oullins, France.
Neuroendocrinology. 1994 May;59(5):483-94. doi: 10.1159/000126695.
GH is synthesized by the somatotrophs in the pituitary, where it may have paracrine actions. In order to identify the GH target cells in rat pituitary, the cellular distributions of rat GH receptor binding protein messenger ribonucleic acid (rGH-RBP mRNA) and protein were investigated at the electronmicroscopic level, using in situ hybridization and immunocytology, respectively, on ultrathin frozen sections of rat pituitary. Ultrastructural distribution of 125I-bGH, 30 min after intracardiac administration was also performed in order to determine the pituitary cell types that bind the labeled hormone. In situ hybridization was performed using digoxigenin-labeled oligonucleotide probe revealed by indirect immunogold reaction. rGH-RBP mRNA was readily identified in the cytoplasmic matrix, associated with the endoplasmic reticulum and the nucleus of the somatotrophs, the lactotrophs and the gonadotrophs. No significant signal was detected in the corticotrophs or thyrotrophs. The number of gold particles in each pituitary cell type was estimated by direct counting, and was compared to the results of hybridization performed on rat liver sections as a control. The results showed that the level of rGH-RBP mRNA was higher in hepatocytes than in the pituitary cells, and was higher in the somatotrophs and lactotrophs than in the gonadotrophs. Immunocytological detection of rGH-RBP was performed using two monoclonal antibodies (mAbs 43 and 263) directed against independent epitopes of the extracellular domain of the rGH-R. Indirect immunocytological detection showed regionalization of rGH-RBP; it was present in the cytoplasmic matrix and the nucleus of the hepatocytes and in discrete pituitary cells: somatotrophs, lactotrophs and gonadotrophs, but not in thyrotrophs or corticotrophs. Gold particle number was also higher in somatotrophs and lactotrophs than in gonadotrophs and higher in the nucleus compared to the cytoplasmic matrix. Radioiodinated GH was uptaken 30 min after injection by the same three pituitary cell types, showing evidence for the functional role of the GH receptor. In conclusion, we find that the cellular localization of rGH-RBP mRNA and protein is similar in discrete cell subpopulations of the pituitary, suggesting a direct effect of GH on somatotrophs, lactotrophs and gonadotrophs, through paracrine, autocrine or intracrine mechanisms.
生长激素（GH）由垂体中的生长激素细胞合成，在垂体中它可能具有旁分泌作用。为了确定大鼠垂体中的GH靶细胞，分别采用原位杂交和免疫细胞化学方法，在大鼠垂体超薄冰冻切片上，从电子显微镜水平研究大鼠生长激素受体结合蛋白信使核糖核酸（rGH-RBP mRNA）和蛋白的细胞分布。为了确定与标记激素结合的垂体细胞类型，还进行了心内注射125I-bGH 30分钟后的超微结构分布研究。使用间接免疫金反应显示的地高辛标记寡核苷酸探针进行原位杂交。rGH-RBP mRNA很容易在细胞质基质中被识别，与生长激素细胞、催乳素细胞和促性腺激素细胞的内质网和细胞核相关。在促肾上腺皮质激素细胞或促甲状腺激素细胞中未检测到明显信号。通过直接计数估计每种垂体细胞类型中的金颗粒数量，并与作为对照的大鼠肝脏切片上进行的杂交结果进行比较。结果表明，rGH-RBP mRNA水平在肝细胞中高于垂体细胞，在生长激素细胞和催乳素细胞中高于促性腺激素细胞。使用针对rGH-R细胞外结构域独立表位的两种单克隆抗体（mAbs 43和263）进行rGH-RBP的免疫细胞化学检测。间接免疫细胞化学检测显示rGH-RBP的区域化；它存在于肝细胞的细胞质基质和细胞核以及离散的垂体细胞中：生长激素细胞、催乳素细胞和促性腺激素细胞，但不存在于促甲状腺激素细胞或促肾上腺皮质激素细胞中。生长激素细胞和催乳素细胞中的金颗粒数量也高于促性腺激素细胞，并且细胞核中的金颗粒数量高于细胞质基质。注射放射性碘标记的GH 30分钟后，同样这三种垂体细胞类型摄取了该激素，这表明生长激素受体具有功能作用。总之，我们发现rGH-RBP mRNA和蛋白在垂体离散细胞亚群中的细胞定位相似，表明生长激素通过旁分泌、自分泌或内分泌机制对生长激素细胞、催乳素细胞和促性腺激素细胞有直接作用。
