Masters B A, Werner H, Roberts C T, LeRoith D, Raizada M K
Department of Physiology, University of Florida College of Medicine, Gainesville 32610.
Endocrinology. 1991 May;128(5):2548-57. doi: 10.1210/endo-128-5-2548.
Astrocytic glial cells from 1- and 21-day-old rat brains were established in primary culture to study the expression of insulin-like growth factor-I (IGF-I) receptors and IGF-I-stimulated glucose transporter (Glut-1). Astrocytes from both age groups expressed specific high affinity IGF-I receptors, whose relative affinities for IGF-I, IGF-II, and insulin were comparable. However, the total number of binding sites and IGF-I receptor mRNA levels were 148% and 240% higher in astrocytes from 21-day-old compared with 1-day-old brains. IGF-I caused a dose-dependent stimulation of [3H]2-deoxy-D-glucose [( 3H]dGlc) uptake in astrocytes from 1-day-old brains. This was associated with increases in Glut-1 protein and mRNA levels. In contrast, astrocytes from 21-day-old brains exhibited a 58% decrease in the binding capacity and a 77% decrease in the steady state levels of Glut-1 protein and its mRNA. In addition, IGF-I failed to stimulate the Glut-1 system in these cells. This lack of IGF-I effect is not due to an alteration inherent to the Glut-1 system, since 12-O-tetradecanoyl-phorbol-13-acetate stimulated [3H]dGlc uptake and Glut-1 protein and its mRNA levels. These observations suggest that changes in basal and IGF-I-stimulated Glut-1 system in brain astrocytes may be developmentally regulated.
为研究胰岛素样生长因子-I（IGF-I）受体和IGF-I刺激的葡萄糖转运蛋白（Glut-1）的表达，将1日龄和21日龄大鼠脑内的星形胶质细胞进行原代培养。两个年龄组的星形胶质细胞均表达特异性高亲和力IGF-I受体，其对IGF-I、IGF-II和胰岛素的相对亲和力相当。然而，与1日龄脑内的星形胶质细胞相比，21日龄脑内星形胶质细胞的结合位点总数和IGF-I受体mRNA水平分别高出148%和240%。IGF-I可引起1日龄脑内星形胶质细胞对[3H]2-脱氧-D-葡萄糖（[3H]dGlc）摄取的剂量依赖性刺激。这与Glut-1蛋白和mRNA水平的增加有关。相比之下，21日龄脑内的星形胶质细胞结合能力下降了58%，Glut-1蛋白及其mRNA的稳态水平下降了77%。此外，IGF-I未能刺激这些细胞中的Glut-1系统。IGF-I效应的缺乏并非由于Glut-1系统固有的改变，因为12-O-十四烷酰佛波醇-13-乙酸酯可刺激[3H]dGlc摄取以及Glut-1蛋白及其mRNA水平。这些观察结果表明，脑星形胶质细胞中基础和IGF-I刺激的Glut-1系统的变化可能受发育调控。
