Zingg H H, Habener J F, Patel Y C
Adv Exp Med Biol. 1985;188:49-58. doi: 10.1007/978-1-4615-7886-4_4.
Our current knowledge of the processes regulating somatostatin biosynthesis is still scarce. Approaches used for the direct investigation of somatostatin biosynthesis in different tissues include 1) analysis of incorporation of labeled amino acids into somatostatin-like immunoreactivity (SLI), 2) cell-free translation of mRNA isolated from SLI producing tissues and 3) analysis of mRNA coding for somatostatin by cDNA blot hybridization. Amino acid incorporation into SLI has been studied in a variety of systems, including anglerfish and rat pancreas, frog retina, rat dorsal root ganglia, cerebral cortex and hypothalamus. We have studied the neuronal biosynthesis of somatostatin using monolayer cultures of neonatal rat hypothalamic cells. Following pulse labeling with [3H]phenylalanine, the cellular extracts contained material that bound specifically to an immobilized anti-somatostatin antibody. Analysis of the bound label by gel chromatography and HPLC provided evidence for the presence of labeled somatostatin-14 (S-14), somatostatin-28 (S-28) and a precursor molecule of Mr 15,000 (15 K SLI). Pulse-chase experiments demonstrated a transfer of label from 15K SLI to material corresponding to S-28 and S-14. Using cloned cDNAs complementary to somatostatin mRNA, the presence of somatostatin mRNA has been demonstrated in anglerfish pancreas and intestine, rat hypothalamus and antrum, as well as in a rat medullary thyroid carcinoma and a rat pancreatic cell line. We have recently studied the developmental regulation of somatostatin gene expression in the rat brain and stomach. Messenger RNA hybridizing specifically to a rat somatostatin cDNA probe was already clearly detectable in tissue extracts derived from brains of one week old rat fetuses. A marked increase of somatostatin mRNA occurred between day 14 and day 21 of embryonic life. By contrast, in tissue extracts derived from stomach, somatostatin mRNA remained undetectable until shortly before birth. These marked differences in the tissue specific regulation of somatostatin gene expression during ontogenesis may reflect basic differences in the developmental regulation of somatostatin gene expression in neural vs. nonneural tissues or may be related to the onset of functional activity in the organs studied.
我们目前对调节生长抑素生物合成过程的了解仍然有限。用于直接研究不同组织中生长抑素生物合成的方法包括：1）分析标记氨基酸掺入生长抑素样免疫反应性物质（SLI）的情况；2）对从产生SLI的组织中分离出的mRNA进行无细胞翻译；3）通过cDNA印迹杂交分析编码生长抑素的mRNA。已在多种系统中研究了氨基酸掺入SLI的情况，包括安康鱼和大鼠胰腺、青蛙视网膜、大鼠背根神经节、大脑皮层和下丘脑。我们利用新生大鼠下丘脑细胞的单层培养物研究了生长抑素的神经元生物合成。用[³H]苯丙氨酸进行脉冲标记后，细胞提取物中含有能与固定化抗生长抑素抗体特异性结合的物质。通过凝胶色谱法和高效液相色谱法对结合的标记物进行分析，证实了标记的生长抑素-14（S-14）、生长抑素-28（S-28）和一个分子量为15,000的前体分子（15K SLI）的存在。脉冲追踪实验表明，标记物从15K SLI转移到了与S-28和S-14相对应的物质中。利用与生长抑素mRNA互补的克隆cDNA，已在安康鱼胰腺和肠道、大鼠下丘脑和胃窦以及大鼠甲状腺髓样癌和大鼠胰腺细胞系中证实了生长抑素mRNA的存在。我们最近研究了大鼠脑和胃中生长抑素基因表达的发育调控。在一周龄大鼠胎儿脑组织提取物中，已能明显检测到与大鼠生长抑素cDNA探针特异性杂交的信使RNA。在胚胎期第14天至第21天之间，生长抑素mRNA显著增加。相比之下，在胃组织提取物中，直到出生前不久才检测到生长抑素mRNA。在个体发育过程中，生长抑素基因表达的组织特异性调控存在这些显著差异，可能反映了神经组织与非神经组织中生长抑素基因表达发育调控的基本差异，也可能与所研究器官功能活动的开始有关。
