Cotransport of water by the Na+/glucose cotransporter
Cotransport of water by the Na+/glucose cotransporter
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DOI：
10.1073/pnas.93.23.13367
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发表时间：
1996-11-12
影响因子：
11.1
通讯作者：
Wright, EM
中科院分区：
文献类型：
--
作者：
Loo, DDF;Zeuthen, T;Wright, EM
在没有流体静力学或渗透梯度的情况下，水穿过上皮细胞膜运输。一个典型的例子是小肠，每天吸收 10 升水。尽管水吸收是活性溶质运输的次要因素，但溶质和水流之间的耦合机制尚不清楚。我们已经测试了这样的假设：水转运通过共转运蛋白（例如刷状缘 Na+/葡萄糖共转运蛋白）与溶质转运直接相关。 Na+/葡萄糖协同转运蛋白在非洲爪蟾卵母细胞中表达，并在糖转运和非转运条件下测量细胞体积的变化。我们证明了 260 个水分子直接与每个运输的糖分子结合，并估计在人体肠道中每天吸收 5 升水。其他动物和植物协同转运蛋白，如 Na+/Cl-/γ-氨基丁酸、Na+/碘化物和 H+/氨基酸转运蛋白也能够转运水，这表明协同转运蛋白在水稳态中发挥重要作用。
Water is transported across epithelial membranes in the absence of ally hydrostatic or osmotic gradients. A prime example is the small intestine, where 10 liters of water are absorbed each day. Although water absorption is secondary to active solute transport, the coupling mechanism between solute and water flow is not understood. We have tested the hypothesis that water transport is directly linked to solute transport by cotransport proteins such as the brush border Na+/glucose cotransporter. The Na+/glucose cotransporter was expressed in Xenopus oocytes, and the changes in cell volume were measured under sugar-transporting and non-transporting conditions. We demonstrate that 260 water molecules are directly coupled to each sugar molecule transported and estimate that in the human intestine this accounts for 5 liters of water absorption per day. Other animal and plant cotransporters such as the Na+/Cl-/gamma-aminobutyric acid, Na+/iodide and H+/amino acid transporters are also able to transport water and this suggests that cotransporters play an important role in water homeostasis.