Fleischer N, Liker H, Stoller T, D'Ambra R, Shields D
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York.
Mol Endocrinol. 1989 Oct;3(10):1652-8. doi: 10.1210/mend-3-10-1652.
Somatostatin (SRIF) is a 14-amino acid peptide hormone that is synthesized as part of a larger precursor, prepro-SRIF, consisting of a signal peptide and a proregion of 80-90 amino acids; mature SRIF is located at the carboxyl-terminus of the precursor. We have used a recombinant retroviral expression vector encoding anglerfish prepor-SRIF-I to infect rat pituitary GH3 cells. The aim of these studies was to investigate the intracellular storage and secretion of the total pool of endogenous GH compared to that of SRIF. Several clonal lines of GH3 cells expressing high or low levels of SRIF were treated with TRH, forskolin, or depolarizing concentrations of potassium, and the levels of intracellular and secreted GH or SRIF were determined using highly sensitive RIAs. Approximately 65% of the total GH was secreted basally, whereas less than 20% of the SRIF-immunoreactive material was basally secreted. Forskolin treatment or potassium depolarization stimulated GH release, but only about 50% above basal levels. In contrast, SRIF secretion was stimulated approximately 5-fold in response to these secretagogues. Based on its lower basal rate of secretion compared to GH and its enhanced release in response to a variety of secretagogues, we conclude that the heterologously expressed SRIF is preferentially targeted to the regulated pathway in GH3 cells.
生长抑素（SRIF）是一种由14个氨基酸组成的肽类激素，它作为一种更大前体——前生长抑素原（prepro - SRIF）的一部分被合成，前生长抑素原由一个信号肽和一个80 - 90个氨基酸的前体区域组成；成熟的SRIF位于前体的羧基末端。我们使用了一种编码安康鱼前生长抑素原 - I的重组逆转录病毒表达载体来感染大鼠垂体GH3细胞。这些研究的目的是调查内源性生长激素（GH）与SRIF总库的细胞内储存和分泌情况。用促甲状腺激素释放激素（TRH）、福斯高林或去极化浓度的钾处理表达高水平或低水平SRIF的几个GH3细胞克隆系，并使用高度敏感的放射免疫分析法（RIA）测定细胞内和分泌的GH或SRIF水平。大约65%的总GH是基础分泌的，而基础分泌的SRIF免疫反应性物质不到20%。福斯高林处理或钾去极化刺激了GH释放，但仅比基础水平高约50%。相比之下，对这些促分泌素的反应中，SRIF分泌被刺激了约5倍。基于其与GH相比更低的基础分泌率以及对多种促分泌素反应中增强的释放，我们得出结论，在GH3细胞中，异源表达的SRIF优先靶向调节性分泌途径。
