Corneal endothelium transports fluid in the absence of net solute transport
Corneal endothelium transports fluid in the absence of net solute transport
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DOI：
10.1016/j.bbamem.2007.05.020
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发表时间：
2007-09-01
影响因子：
3.4
通讯作者：
Fischbarg, Jorge
中科院分区：
文献类型：
--
作者：
Diecke, Friedrich P. J.;Ma, Li;Fischbarg, Jorge
角膜内皮将液体从角膜基质输送到房水，从而通过保持基质相对脱水来维持基质透明度。这种液体转运机制被认为是由 HCO3- 和 Cl- 沿同一方向（从基质到房水）的跨细胞转运驱动的。与这些阴离子运动平行，为了实现电中性，存在沿相同方向的细胞旁 Na+ 和跨细胞 K+ 传输。由此产生的溶质净流可能会产生驱动流体输送的局部渗透梯度。然而，有报道称，名义上不含 HCO3 的溶液中仍有大约 50% 的残留流体输送。我们已经研究了这种残余液体输送的驱动力。我们确认，在名义上不含 HCO3 的溶液中，48% 的控制流体运输仍然存在。当另外抑制Cl-通道时，仍保留30%的控制流体运动。添加碳酸酐酶抑制剂没有进一步的作用。这些操作结合起来抑制所有阴离子的跨细胞转运，没有阴离子，就不可能有任何溶质的净转运，因此不存在局部渗透梯度，但仍存在残留的液体运动。只有进一步添加苯扎米尔（一种上皮 Na+ 通道抑制剂）才能完全消除液体转运。我们的数据与跨细胞局部渗透不一致，而是支持电渗耦合驱动的细胞旁流体运输的范例。 (C) 2007 Elsevier B.V. 保留所有权利。
The comeal endothelium transports fluid from the comeal stroma to the aqueous humor, thus maintaining stromal transparency by keeping it relatively dehydrated. This fluid transport mechanism is thought to be driven by the transcellular transports of HCO3- and Cl- in the same direction, from stroma to aqueous. In parallel to these anion movements, for electroneutrality, there are paracellular Na+ and transcellular K+ transports in the same direction. The resulting net flow of solute might generate local osmotic gradients that drive fluid transport. However, there are reports that some 50% residual fluid transport remains in nominally HCO3 free solutions. We have examined the driving force for this residual fluid transport. We confirm that in nominally HCO3- free solutions, 48% of control fluid transport remains. When in addition Cl- channels are inhibited, 30% of control fluid movement still remains. Addition of a carbonic anhydrase inhibitor has no further effect. These manipulations combined inhibit the transcellular transport of all anions, without which there cannot be any net transport of solute and consequently no local osmotic gradients, yet there is residual fluid movement. Only the further addition of benzamil, an inhibitor of epithelial Na+ channels, abolishes fluid transport completely. Our data are]inconsistent with transcellular local osmosis and instead support the paradigm of paracellular fluid transport driven by electro-osmotic coupling. (C) 2007 Elsevier B.V. All rights reserved.