Cotransport of water by the Na+-K+-2Cl- cotransporter NKCC1 in mammalian epithelial cells
Cotransport of water by the Na+-K+-2Cl- cotransporter NKCC1 in mammalian epithelial cells
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DOI：
10.1113/jphysiol.2010.194738
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发表时间：
2010-11-01
影响因子：
5.5
通讯作者：
Alvarez-Leefmans, Francisco J.
中科院分区：
文献类型：
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作者：
Hamann, Steffen;Herrera-Perez, Jose J.;Alvarez-Leefmans, Francisco J.
在胎儿人眼睫状体色素上皮（PE）细胞的汇合培养物中研究了Na + -K + -2Cl（-）协同转运蛋白（NKCC1）的水转运。由 NKCC1 介导的水、Na+ 和 Cl- 通量之间的相互依赖性是从细胞水体积的变化推断出来的，并通过荧光染料钙黄绿素的细胞内自猝灭进行监测。等渗去除外部 Cl- 或 Na+ 导致水从细胞中快速流出，这种情况被布美他尼 (10 μM) 抑制。当返回到对照溶液时，水快速流入，需要同时存在外部 Na+ 和 Cl-。水流入可能会逆着跨膜渗透梯度向上坡进行，这表明离子通量中包含的能量可以转移到水通量中。外部[Cl-]变化引起的水流入以S形方式饱和，K-m为60 mm，而外部[Na+]变化引起的水流入遵循一级动力学，K-m约为40 mM。这些参数与 NKCC1 介导的离子传输一致。我们的发现支持了之前的一项研究，其中我们表明 NKCC1 的水运输是离子梯度和渗透梯度之间平衡的结果。 NKCC1 中盐和水运输之间的耦合代表了细胞水稳态的一个新方面，其中细胞可以独立于跨膜渗透梯度的方向改变其体积。这与上皮细胞和对称细胞都有相关性。
Water transport by the Na+-K+-2Cl(-) cotransporter (NKCC1) was studied in confluent cultures of pigmented epithelial (PE) cells from the ciliary body of the fetal human eye. Interdependence among water, Na+ and Cl- fluxes mediated by NKCC1 was inferred from changes in cell water volume, monitored by intracellular self-quenching of the fluorescent dye calcein. Isosmotic removal of external Cl- or Na+ caused a rapid efflux of water from the cells, which was inhibited by bumetanide (10 mu M). When returned to the control solution there was a rapid water influx that required the simultaneous presence of external Na+ and Cl-. The water influx could proceed uphill, against a transmembrane osmotic gradient, suggesting that energy contained in the ion fluxes can be transferred to the water flux. The influx of water induced by changes in external [Cl-] saturated in a sigmoidal fashion with a K-m of 60 mm, while that induced by changes in external [Na+] followed first order kinetics with a K-m of about 40 mM. These parameters are consistent with ion transport mediated by NKCC1. Our findings support a previous investigation, in which we showed water transport by NKCC1 to be a result of a balance between ionic and osmotic gradients. The coupling between salt and water transport in NKCC1 represents a novel aspect of cellular water homeostasis where cells can change their volume independently of the direction of an osmotic gradient across the membrane. This has relevance for both epithelial and symmetrical cells.