Lotan R M, Barzilai D
Endocrine Institute, Rambam Medical Center, Haifa, Israel.
Isr J Med Sci. 1990 Jan;26(1):5-11.
In Madin-Darby canine kidney (MDCK) cells, specific plasma membrane binding of [125I]insulin was undetectable. Correspondingly, neither insulin-stimulated incorporation of [14C]glucose into glycogen nor insulin-induced uptake of radiolabeled alpha-aminoisobutyrate ([ 3H]AIB) could be demonstrated. These results suggested that MDCK cells lack specific cell surface insulin receptors. To further examine this question intact MDCK cells were preincubated with antireceptor serum and subsequently labeled with [125I]protein A; however, insulin receptors were not detected. Control H4 hepatoma cells bound insulin, responded with increased glycogen synthesis and amino acid uptake, and possessed immunologically recognizable insulin receptor components. The insulin-associated response of stimulated [3H]AIB uptake was induced in MDCK cells by the insulinomimetic lectins concanavalin A (130-140% of basal value at concentrations of 10-40 micrograms/ml) and wheat germ agglutinin (140-160% of basal value at concentrations of 10-30 micrograms/ml). This stimulation was abolished by the respective lectin-specific monosaccharides D-mannose and N-acetyl-D-glucosamine. Together, these data indicate that the insulin-like activity of concanavalin A and wheat germ agglutinin can be elicited in MDCK cells even in the apparent absence of specific plasma membrane insulin-binding sites.
在犬肾传代细胞（MDCK）中，未检测到[125I]胰岛素与特定质膜的结合。相应地，既未证实胰岛素刺激[14C]葡萄糖掺入糖原，也未证实胰岛素诱导放射性标记的α-氨基异丁酸（[3H]AIB）的摄取。这些结果表明，MDCK细胞缺乏特异性细胞表面胰岛素受体。为了进一步研究这个问题，将完整的MDCK细胞与抗受体血清预孵育，随后用[125I]蛋白A进行标记；然而，未检测到胰岛素受体。对照H4肝癌细胞能结合胰岛素，糖原合成增加且氨基酸摄取有反应，并拥有可通过免疫识别的胰岛素受体成分。胰岛素模拟凝集素刀豆球蛋白A（在浓度为10 - 40微克/毫升时为基础值的130 - 140%）和麦胚凝集素（在浓度为10 - 30微克/毫升时为基础值的140 - 160%）可诱导MDCK细胞中受刺激的[3H]AIB摄取的胰岛素相关反应。这种刺激被各自的凝集素特异性单糖D - 甘露糖和N - 乙酰 - D - 葡萄糖胺消除。总之，这些数据表明，即使明显缺乏特异性质膜胰岛素结合位点，刀豆球蛋白A和麦胚凝集素的胰岛素样活性仍可在MDCK细胞中引发。
