Sato Y, Ito T, Udaka N, Kanisawa M, Noguchi Y, Cushman S W, Satoh S
Department of Pathology, Yokohama City University School of Medicine, Japan.
Tissue Cell. 1996 Dec;28(6):637-43. doi: 10.1016/s0040-8166(96)80067-x.
The subcellular localization of five isoforms of facilitated-diffusion glucose transporters (GLUTs), from GLUT1 to GLUT5, in rat pancreatic islets was studied by immunohistochemistry using rabbit polyclonal antisera against mouse or rat GLUT peptides. Animals were perfusion-fixed with phosphate-buffered 4% paraformaldehyde and the pancreases were removed. Some specimens were embedded in paraffin, serially sectioned, and immunostained for glucagon, insulin, somatostatin, and the GLUTs for light microscopic observation. Others were prepared for immunoelectron microscopy by the post-embedding method. By these methods, GLUT2 immunostaining was observed on the lateral membranes of pancreatic beta-cells, whereas GLUT3 immunoreaction was predominantly localized in the cytoplasm of beta-cells and was not found in alpha-cells. In contrast, GLUT5 immunostaining was preferentially localized in the cytoplasm of alpha-cells compared to that of beta-cells. However, GLUT1 and GLUT4 were either barely or not at all detectable in any cells. These results suggest that rat islets take up glucose by at least three different processes and that blood glucose levels could be modulated differentially by: a high Km glucose transporter, GLUT2, in beta-cells; by a low Km glucose transporter, GLUT3, in beta-cells; and by a low Km glucose transporter, GLUT5, in alpha-cells.
利用抗小鼠或大鼠葡萄糖转运蛋白（GLUT）肽段的兔多克隆抗血清，通过免疫组织化学方法研究了大鼠胰岛中促进扩散型葡萄糖转运蛋白（GLUT1至GLUT5）五种同工型的亚细胞定位。动物用磷酸盐缓冲的4%多聚甲醛进行灌注固定，然后取出胰腺。一些标本用石蜡包埋，连续切片，并对胰高血糖素、胰岛素、生长抑素和GLUT进行免疫染色，用于光学显微镜观察。其他标本则采用包埋后法制备用于免疫电子显微镜观察。通过这些方法，在胰腺β细胞的侧膜上观察到GLUT2免疫染色，而GLUT3免疫反应主要定位于β细胞的细胞质中，在α细胞中未发现。相反，与β细胞相比，GLUT5免疫染色优先定位于α细胞的细胞质中。然而，在任何细胞中几乎都检测不到GLUT1和GLUT4，或者根本检测不到。这些结果表明，大鼠胰岛至少通过三种不同的过程摄取葡萄糖，并且血糖水平可能通过以下方式受到不同调节：β细胞中的高Km葡萄糖转运蛋白GLUT2；β细胞中的低Km葡萄糖转运蛋白GLUT3；以及α细胞中的低Km葡萄糖转运蛋白GLUT5。
