Functional Ion Channels in Pulmonary Alveolar Type I Cells Support a Role for Type I Cells in Lung Ion Transport

Efficient gas exchange in the lungs depends on regulation of the amount of fluid in the thin (average 0.2 μm) liquid layer lining the alveolar epithelium. Fluid fluxes are regulated by ion transport across the alveolar epithelium, which is composed of alveolar type I (TI) and type II (TII) cells. Th...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2006-03, Vol.103 (13), p.4964-4969
Main Authors: Johnson, Meshell D., Bao, Hui-Fang, Helms, My N., Chen, Xi-Juan, Tigue, Zac, Jain, Lucky, Dobbs, Leland G., Eaton, Douglas C.
Format: Article
Language:English
Subjects:
Animals
Biological Sciences
Cations
Cations - chemistry
Cell membranes
Cells
Cellular biology
Cultured cells
Electrophysiology
Epithelial cells
Epithelium
Fluids
Heart
Immunohistochemistry
Ion Channel Gating
Ion channels
Ion Channels - genetics
Ion Channels - metabolism
Ion Transport
Ions
Lungs
Nucleotides, Cyclic - metabolism
Patch-Clamp Techniques
Physiological regulation
Protein Subunits - genetics
Protein Subunits - metabolism
Pulmonary alveoli
Pulmonary Alveoli - cytology
Pulmonary Alveoli - metabolism
Rats
Rats, Sprague-Dawley
RNA, Messenger - genetics
Sodium
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Summary:Efficient gas exchange in the lungs depends on regulation of the amount of fluid in the thin (average 0.2 μm) liquid layer lining the alveolar epithelium. Fluid fluxes are regulated by ion transport across the alveolar epithelium, which is composed of alveolar type I (TI) and type II (TII) cells. The accepted paradigm has been that TII cells, which cover 95% of the surface area, provide a route for water absorption. Here we present data that TI cells contain functional epithelial Na⁺ channels (ENaC), pimozide-sensitive cation channels, K⁺ channels, and the cystic fibrosis transmembrane regulator. TII cells contain ENaC and cystic fibrosis transmembrane regulator, but few pimozide-sensitive cation channels. These findings lead to a revised paradigm of ion and water transport in the lung in which (i) Na⁺ and Cl⁻ transport occurs across the entire alveolar epithelium (TI and TII cells) rather than only across TII cells; and (ii) by virtue of their very large surface area, TI cells are responsible for the bulk of transepithelial Na⁺ transport in the lung.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0600855103