Larsen P J, Bersani M, Holst J J, Møller M, Mikkelsen J D
Institute of Medical Anatomy B, University of Copenhagen, Denmark.
J Neurosci. 1992 Mar;12(3):946-61. doi: 10.1523/JNEUROSCI.12-03-00946.1992.
Antisera raised against various synthetic peptide fragments of the pro-somatostatin molecule were used to visualize immunohistochemically the distributions of different pro-somatostatin fragments in the hypothalamus and posterior pituitary of the Mongolian gerbil. To define the nature of the immunoreactive somatostatin-related molecular forms, gel chromatography combined with radioimmunoassays of hypothalamic and posterior pituitary extracts was performed. Within the hypothalamus, only trace amounts of somatostatin-28 and somatostatin-28(1-12) were present, whereas pro-somatostatin(1-76), pro-somatostatin(1-64), and somatostatin-14 peptides were present in equimolar amounts. In contrast, the posterior pituitary lobe contained equal amounts of somatostatin-14, somatostatin-28, and somatostatin-28(1-12) but no pro-somatostatin(1-76), indicating that pro-somatostatin is further processed during the axonal flow to posterior pituitary nerve terminals. The gel chromatographic data were further substantiated by immunohistochemical data. Thus, perikarya containing all of these five immunoreactivities were strictly confined to the periventricular area and parvocellular subset of the paraventricular nucleus. However, the number of somatostatin-28- and somatostatin-28(1-12)-immunoreactive perikarya was approximately 20% of the number of somatostatin-14- and pro-somatostatin(1-64)-immunoreactive cells. In other hypothalamic areas only somatostatin-14 and pro-somatostatin(1-64) immunoreactivities were detectable in cell bodies. These cell bodies were encountered in the organum vasculosum laminae terminalis; the suprachiasmatic, ventromedial, arcuate, perifornical, and posterior hypothalamic nuclei; and the median preoptic and retrochiasmatic areas. In situ hybridization histochemistry revealed that the cellular distribution of pro-somatostatin mRNA corresponds to that of somatostatin-14 and pro-somatostatin immunoreactivity, suggesting that the immunoreactive material observed within the cell bodies is synthetized there and that the differences in density of immunoreactivities may be explained by intracellular processing of pro-somatostatin. Somatostatinergic nerve fibers and terminals in hypothalamic areas and the posterior pituitary lobe were immunoreactive to all of the employed antisera. From the present results, obvious differences between intrahypothalamic and hypothalamo-pituitary somatostatinergic neurons emerge. Within hypothalamic neurons not projecting to the median eminence and the posterior pituitary lobe, pro-somatostatin is posttranslationally processed in the cell body predominantly into pro-somatostatin(1-64) and somatostatin-14. Otherwise, within periventricular neurons projecting to the median eminence and the posterior pituitary lobe, pro-somatostatin is posttranslationally processed during the axonal flow into pro-somatostatin(1-64), somatostatin-14, somatostatin-28, and somatostatin-28(1-12).
用针对促生长抑素分子不同合成肽片段制备的抗血清，通过免疫组织化学方法观察了不同促生长抑素片段在蒙古沙鼠下丘脑和垂体后叶中的分布。为确定免疫反应性生长抑素相关分子形式的性质，对下丘脑和垂体后叶提取物进行了凝胶色谱分析并结合放射免疫测定。下丘脑内仅存在痕量的生长抑素-28和生长抑素-28(1-12)，而促生长抑素(1-76)、促生长抑素(1-64)和生长抑素-14肽以等摩尔量存在。相反，垂体后叶中生长抑素-14、生长抑素-28和生长抑素-28(1-12)含量相等，但不存在促生长抑素(1-76)，这表明促生长抑素在轴浆运输至垂体后叶神经末梢的过程中会进一步加工。凝胶色谱数据得到了免疫组织化学数据的进一步证实。因此，含有所有这五种免疫反应性的核周体严格局限于室周区和室旁核的小细胞亚群。然而，生长抑素-28和生长抑素-28(1-12)免疫反应性核周体的数量约为生长抑素-14和促生长抑素(1-64)免疫反应性细胞数量的20%。在其他下丘脑区域，仅在细胞体中可检测到生长抑素-14和促生长抑素(1-64)免疫反应性。这些细胞体见于终板血管器、视交叉上核、腹内侧核、弓状核、穹窿周核和下丘脑后核，以及视前正中核和视交叉后区。原位杂交组织化学显示，促生长抑素mRNA的细胞分布与生长抑素-14和促生长抑素免疫反应性的分布一致，提示在细胞体内观察到的免疫反应性物质是在那里合成的，免疫反应性密度的差异可能由促生长抑素的细胞内加工来解释。下丘脑区域和垂体后叶中的生长抑素能神经纤维和终末对所有使用的抗血清均有免疫反应性。根据目前的结果，下丘脑内和下丘脑-垂体生长抑素能神经元之间出现了明显差异。在下丘脑内不投射至正中隆起和垂体后叶的神经元中，促生长抑素在细胞体内主要经翻译后加工为促生长抑素(1-64)和生长抑素-14。否则，在投射至正中隆起和垂体后叶的室周神经元中，促生长抑素在轴浆运输过程中经翻译后加工为促生长抑素(1-64)、生长抑素-14、生长抑素-28和生长抑素-28(1-12)。
