Ginsberg B H, Brown T J
Metabolism. 1982 Jul;31(7):728-32. doi: 10.1016/0026-0495(82)90205-0.
Previous studies using inhibitors have suggested that protein synthesis is necessary for "down-regulation" of insulin receptors. We have tested this hypothesis without the use of inhibitors by studying the ability of cells of the erythroid series to down-regulate their insulin receptors in vitro. The cells tested include mature erythrocytes and reticulocytes from rabbits and Friend erythroleukemia cells (a model for the basophilic erythroblast, a primitive nucleated erythrocyte). All cells were maintained at 37 degrees C for 18 hr +/- insulin (10(-8)M). Cultures were then incubated with phosphate buffered salines (pH 7.0) at 30 degrees C for 40 min to remove bound insulin. Receptors were quantitated by computerized analysis of Scatchard plots of subsequent insulin binding studies. Cells fully capable of both mRNA synthesis and protein synthesis, such as the undifferentiated and differentiated Friend erythroleukemia cell, had reduction of insulin receptors at 60% and 43%, respectively. Reticulocytes, which were capable of protein synthesis but not mRNA synthesis, had decreases of 25%-30% in 8 separate experiments. Mature erythrocytes, capable of neither RNA nor protein synthesis had no significant changes in receptor concentrations. Since mature erythrocytes do not "down-regulate" their insulin receptor concentration, studies of these receptors in erythrocytes of patients should be interpreted with caution.
以往使用抑制剂的研究表明，蛋白质合成对于胰岛素受体的“下调”是必要的。我们通过研究红系细胞在体外下调其胰岛素受体的能力，在不使用抑制剂的情况下检验了这一假设。所测试的细胞包括来自兔子的成熟红细胞和网织红细胞以及弗瑞德红白血病细胞（一种嗜碱性成红细胞模型，嗜碱性成红细胞是一种原始的有核红细胞）。所有细胞在37℃下培养18小时，±胰岛素（10⁻⁸M）。然后将培养物在30℃下用磷酸盐缓冲盐水（pH 7.0）孵育40分钟以去除结合的胰岛素。通过对后续胰岛素结合研究的Scatchard图进行计算机分析来定量受体。完全能够进行mRNA合成和蛋白质合成的细胞，如未分化和分化的弗瑞德红白血病细胞，胰岛素受体分别减少了60%和43%。能够进行蛋白质合成但不能进行mRNA合成的网织红细胞，在8次独立实验中减少了25%-30%。既不能进行RNA合成也不能进行蛋白质合成的成熟红细胞，其受体浓度没有显著变化。由于成熟红细胞不会“下调”其胰岛素受体浓度，因此在患者红细胞中对这些受体的研究应谨慎解释。
