rENaC is the predominant Na+ channel in the apical membrane of the rat renal inner medullary collecting duct

Kenneth A Volk; Rita D Sigmund; Peter M Snyder; Fiona J McDonald; Michael J Welsh; John B Stokes

doi:10.1172/JCI118344

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rENaC is the predominant Na+ channel in the apical membrane of the rat renal inner medullary collecting duct

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rENaC is the predominant Na+ channel in the apical membrane of the rat renal inner medullary collecting duct

Kenneth A Volk, Rita D Sigmund, Peter M Snyder, Fiona J McDonald, Michael J Welsh and John B Stokes

The Journal of clinical investigation, Vol.96(6), pp.2748-2757

12/1995

DOI: 10.1172/JCI118344

PMCID: PMC185984

PMID: 8675644

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Abstract

The terminal nephron segment, the inner medullary collecting duct (IMCD), absorbs Na+ by an electrogenic process that involves the entry through an apical (luminal) membrane Na+ channel. To understand the nature of this Na+ channel, we employed the patch clamp technique on the apical membrane of primary cultures of rat IMCD cells grown on permeable supports. We found that all ion channels detected in the cell-attached configuration were highly selective for Na+ (Li+) over K+. The open/closed transitions showed slow kinetics, had a slope conductance of 6-11 pS, and were sensitive to amiloride and benzamil. Nonselective cation channels with a higher conductance (25-30 pS), known to be present in IMCD cells, were not detected in the cell-attached configuration, but were readily detected in excised patches. The highly selective channels had properties similar to the recently described rat epithelial Na+ channel complex, rENaC. We therefore asked whether rENaC mRNA was present in the IMCD. We detected mRNA for all three rENaC subunits in rat renal papilla and also in primary cultures of the IMCD. Either glucocorticoid hormone or mineralocorticoid hormone increased the amount of alpha-rENaC subunit mRNA but had no effect on the mRNA level of the beta-rENaC or gamma-rENaC subunits. From these data, taken in the context of other studies on the characteristics of Na+ selective channels and the distribution of rENaC mRNA, we conclude that steroid stimulated Na+ absorption by the IMCD is mediated primarily by Na+ channels having properties of the rENaC subunit complex.

Details

Title: Subtitle: rENaC is the predominant Na+ channel in the apical membrane of the rat renal inner medullary collecting duct
Creators: Kenneth A Volk - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA
Rita D Sigmund - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA
Peter M Snyder - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA
Fiona J McDonald - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA
Michael J Welsh - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA
John B Stokes - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242, USA
Resource Type: Journal article
Publication Details: The Journal of clinical investigation, Vol.96(6), pp.2748-2757
DOI: 10.1172/JCI118344
PMID: 8675644
PMCID: PMC185984
ISSN: 0021-9738
eISSN: 1558-8238
Language: English
Date published: 12/1995
Academic Unit: Neurology; Molecular Physiology and Biophysics; Pulmonary, Critical Care, and Occupational Medicine; Cardiovascular Medicine; Fraternal Order of Eagles Diabetes Research Center; Neurosurgery; Medicine Administration; Internal Medicine
Record Identifier: 9984013112102771

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