Román Y, Alfonso A, Louzao M C, Vieytes M R, Botana L M
Departamento de Farmacología, Universidad de Santiago de Compostela, Facultad de Veterinaria, 27002 Lugo, Spain.
Pflugers Arch. 2001 Nov;443(2):234-9. doi: 10.1007/s004240100677.
D-Glucose uptake in isolated rabbit enterocytes was studied using confocal microscopy and 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-D-glucose (2-NDBG), a D-glucose fluorescent analogue, by analysing the fluorescence of apical and basal enterocyte zones. Under normal conditions, apical fluorescence was always higher than basal, presumably due to the location of the Na+-D-glucose cotransporter in the brush-border membrane. After blocking this transporter with phlorizin, apical and basal fluorescence values were similar. This suggests that both brush-border and basolateral membranes participate in phlorizin-insensitive D-glucose transport, since transport across only one membrane cannot explain the uniform overall fluorescence observed. Similarly, after inhibiting the Na+-D-glucose cotransporter by incubating the enterocytes in a medium containing 0.5 mM Na+, neither apical nor basal fluorescence predominated. In contrast, with 130.5 mM extracellular Na+, apical fluorescence was clearly higher than basal fluorescence. These results suggest that phlorizin-insensitive, Na+-independent 2-NDBG uptake occurred through both brush-border and basolateral membranes, probably via the glucose uniporters GLUT2 and GLUT5, suggesting that the latter is a D-glucose transporter.
利用共聚焦显微镜和2-[N-(7-硝基苯并-2-恶唑-1,3-二氮杂萘-4-基)氨基]-2-脱氧-D-葡萄糖(2-NDBG，一种D-葡萄糖荧光类似物)，通过分析肠上皮细胞顶端和基底区域的荧光，研究了分离的兔肠上皮细胞对D-葡萄糖的摄取。在正常情况下，顶端荧光总是高于基底荧光，这可能是由于Na+-D-葡萄糖共转运蛋白位于刷状缘膜上。用根皮苷阻断该转运蛋白后，顶端和基底荧光值相似。这表明刷状缘膜和基底外侧膜都参与了对根皮苷不敏感的D-葡萄糖转运，因为仅通过一层膜的转运无法解释观察到的均匀整体荧光。同样，在含有0.5 mM Na+的培养基中孵育肠上皮细胞以抑制Na+-D-葡萄糖共转运蛋白后，顶端和基底荧光均不占优势。相反，在细胞外Na+浓度为130.5 mM时，顶端荧光明显高于基底荧光。这些结果表明，对根皮苷不敏感、不依赖Na+的2-NDBG摄取通过刷状缘膜和基底外侧膜发生，可能是通过葡萄糖单向转运体GLUT2和GLUT5，这表明后者是一种D-葡萄糖转运体。
