Takata K, Kasahara T, Kasahara M, Ezaki O, Hirano H
Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan.
Cell Tissue Res. 1992 Jan;267(1):3-9. doi: 10.1007/BF00318685.
Glucose is actively absorbed via a Na(+)-dependent active glucose transporter (Na-GT) in the small intestine. We raised a polyclonal antibody against the peptide corresponding to amino acids 564-575 of rabbit intestinal Na-GT, and localized it immunohistochemically in the rat jejunum. By means of immunofluorescence staining, Na-GT was located at the brush border of the absorptive epithelial cells of the intestinal villi. Electron-microscopic examination showed that Na-GT was localized at the plasma membrane of the apical microvilli of these cells. Little Na-GT was found at the basolateral plasma membrane. Along the crypt-villus axis, all of the absorptive epithelial cells in the villus were positive for Na-GT. In addition to the brush border staining, the supranuclear positive staining, which was shown to be the Golgi apparatus by use of electron microscopy, was seen in cells located between the base to the middle of the villus. Cells in crypts exhibited little or no staining for Na-GT. Goblet cells scattered in the intestinal epithelium were negative for Na-GT staining. These observations show that Na-GT is specific to the apical plasma membrane of the absorptive epithelial cells, and that the onset of Na-GT synthesis may occur near the crypt-villus junction.
葡萄糖通过小肠中一种依赖钠离子的主动葡萄糖转运蛋白（Na-GT）被主动吸收。我们制备了一种针对兔肠道Na-GT氨基酸564 - 575对应肽段的多克隆抗体，并通过免疫组织化学方法将其定位在大鼠空肠中。通过免疫荧光染色，Na-GT位于肠绒毛吸收性上皮细胞的刷状缘。电子显微镜检查显示，Na-GT定位于这些细胞顶端微绒毛的质膜上。在基底外侧质膜上几乎没有发现Na-GT。沿着隐窝 - 绒毛轴，绒毛中的所有吸收性上皮细胞Na-GT均呈阳性。除了刷状缘染色外，在绒毛底部到中部之间的细胞中还可见核上阳性染色，通过电子显微镜观察证实为高尔基体。隐窝中的细胞对Na-GT染色很少或无染色。散在于肠上皮中的杯状细胞对Na-GT染色呈阴性。这些观察结果表明，Na-GT对吸收性上皮细胞的顶端质膜具有特异性，并且Na-GT合成的起始可能发生在隐窝 - 绒毛交界处附近。
