Shiu R P, Paterson J A
Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Endocrinology. 1988 Sep;123(3):1456-60. doi: 10.1210/endo-123-3-1456.
This study compares the molecular characteristics of the insulin-like growth factor II (IGF-II) peptides synthesized and secreted by explants of neonatal brain and adult pituitary of rat to those produced by the Buffalo rat liver cell line (BRL-3A). Metabolic labeling, followed by immunoprecipitation and sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the rat brain and liver cells synthesized and secreted the following immunoreactive IGF-II peptides: 19, 11, 10, and 8.7 kilodaltons (kd), whereas the rat pituitary secreted the 10 and 8.7 kd peptides. However, the brain and pituitary explants failed to secrete the mature 7.5 kd IGF-II peptide which was a major species secreted by the liver cells. In the brain and pituitary, the predominant form of IGF-II peptide secreted was the 8.7 kd. This result suggests that 1) different mechanisms of processing of the IGF-II precursor and/or the preferential translation of different messenger RNA (mRNA) species may exist in different cell types, and 2) the 8.7 kd IGF-II peptide may be the biologically relevant molecule in the central nervous system of the rat.
本研究比较了大鼠新生脑和成年垂体的外植体合成与分泌的胰岛素样生长因子II（IGF-II）肽的分子特征，以及布法罗大鼠肝细胞系（BRL-3A）产生的IGF-II肽的分子特征。代谢标记，随后进行免疫沉淀和十二烷基硫酸钠聚丙烯酰胺凝胶电泳，结果显示大鼠脑和肝细胞合成并分泌了以下具有免疫反应性的IGF-II肽：19、11、10和8.7千道尔顿（kd），而大鼠垂体分泌的是10和8.7 kd的肽。然而，脑和垂体外植体未能分泌成熟的7.5 kd IGF-II肽，而该肽是肝细胞分泌的主要形式。在脑和垂体中，分泌的IGF-II肽的主要形式是8.7 kd。这一结果表明：1）不同细胞类型中可能存在IGF-II前体加工的不同机制和/或不同信使核糖核酸（mRNA）种类的优先翻译；2）8.7 kd IGF-II肽可能是大鼠中枢神经系统中具有生物学相关性的分子。
