Document Detail

Cotransport of water by the Na+-K+-2Cl(-) cotransporter NKCC1 in mammalian epithelial cells.
MedLine Citation:
PMID:  20819947     Owner:  NLM     Status:  MEDLINE    
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 μm). 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 Km of 60 mm, while that induced by changes in external [Na+] followed first order kinetics with a Km 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.
Steffen Hamann; José J Herrera-Perez; Thomas Zeuthen; Francisco J Alvarez-Leefmans
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of physiology     Volume:  588     ISSN:  1469-7793     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2010 Nov 
Date Detail:
Created Date:  2010-11-09     Completed Date:  2011-03-10     Revised Date:  2013-05-28    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  4089-101     Citation Subset:  IM    
Nordic Centre for Water Imbalance Related Disorders, Institute of Cellular and Molecular Medicine, The Panum Institute, University of Copenhagen, Copenhagen, Denmark.
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MeSH Terms
Biological Transport / physiology
Bumetanide / pharmacology
Cell Membrane Permeability / drug effects,  physiology*
Cells, Cultured
Chlorides / pharmacokinetics
Ciliary Body / cytology,  physiology*
Epithelial Cells / cytology,  physiology*
Osmosis / physiology
Protein Isoforms / physiology
Sodium / pharmacokinetics
Sodium Potassium Chloride Symporter Inhibitors / pharmacology
Sodium-Potassium-Chloride Symporters / physiology*
Water / metabolism*
Reg. No./Substance:
0/Chlorides; 0/Protein Isoforms; 0/Sodium Potassium Chloride Symporter Inhibitors; 0/Sodium-Potassium-Chloride Symporters; 0/sodium-potassium-chloride cotransporter 1 protein; 28395-03-1/Bumetanide; 7440-23-5/Sodium; 7732-18-5/Water
Comment In:
J Physiol. 2010 Nov 1;588(Pt 21):4063-4   [PMID:  21037312 ]
J Physiol. 2011 Feb 15;589(Pt 4):781-2   [PMID:  21486847 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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