Lee S H, Pritchard J B
Am J Physiol. 1983 Mar;244(3):F278-88. doi: 10.1152/ajprenal.1983.244.3.F278.
Brush border membrane vesicles were prepared from striped mullet (Mugil cephalus) kidney. As judged by the marker enzyme activities, these membranes were enriched 10- to 15-fold compared with the initial homogenate. Uptake of D-glucose was phlorizin sensitive and Na+ dependent. L-glucose uptake was unaffected by either phlorizin or Na+. D-Glucose uptake reflected entry into the osmotically active intravesicular space, not binding to the membranes. When Na+ was increased from 25 to 100 mM, the maximum velocity of glucose uptake was increased from 92 to 423 pmol . s-1 . mg protein-1, whereas the apparent Km (1.27 +/- 0.23) was not altered as Na+ increased. 22Na+ uptake by these membrane vesicles was stimulated by D-glucose and inhibited by phlorizin. These results indicated that Na+ and glucose entered the vesicles via a cotransport process. Consistent with this interpretation, it was possible to show that glucose uptake could be driven by either the chemical or electrical component of the Na+ electrochemical gradient and that the contributions of these two components were additive when both were present. Finally, it was shown that the coupling ratio between Na+ and glucose was approximately 1:1. Accordingly, these results indicate that reabsorption of D-glucose across the brush border membranes is coupled to the transmembrane electrochemical gradient of sodium ions.
从条纹鲻鱼（Mugil cephalus）肾脏制备刷状缘膜囊泡。根据标记酶活性判断，这些膜与初始匀浆相比富集了10至15倍。D-葡萄糖的摄取对根皮苷敏感且依赖于Na⁺。L-葡萄糖的摄取不受根皮苷或Na⁺的影响。D-葡萄糖的摄取反映了进入具有渗透活性的囊泡内空间，而不是与膜结合。当Na⁺浓度从25 mM增加到100 mM时，葡萄糖摄取的最大速度从92增加到423 pmol·s⁻¹·mg蛋白⁻¹，而表观Km（1.27±0.23）并未随Na⁺增加而改变。这些膜囊泡对²²Na⁺的摄取受到D-葡萄糖的刺激并被根皮苷抑制。这些结果表明Na⁺和葡萄糖通过共转运过程进入囊泡。与该解释一致的是，可以证明葡萄糖摄取可以由Na⁺电化学梯度的化学或电成分驱动，并且当两者都存在时这两个成分的贡献是相加的。最后，表明Na⁺与葡萄糖之间的偶联比约为1:1。因此，这些结果表明D-葡萄糖跨刷状缘膜的重吸收与钠离子的跨膜电化学梯度偶联。
