In:
American Journal of Physiology-Lung Cellular and Molecular Physiology, American Physiological Society, Vol. 282, No. 4 ( 2002-04-01), p. L631-L641
Abstract:
H441 cells, a bronchiolar epithelial cell line, develop a glucocorticoid-regulated amiloride-sensitive Na + transport pathway on permeable supports (R. Sayegh, S. D. Auerbach, X. Li, R. Loftus, R. Husted, J. B. Stokes, and C. P. Thomas. J Biol Chem 274: 12431–12437, 1999). To understand its molecular basis, we examined the effect of glucocorticoids (GC) on epithelial Na + channel (ENaC)-α, -β, and -γ and sgk1 expression and determined the biophysical properties of Na + channels in these cells. GC stimulated the expression of ENac-α, -β, and -γ and sgk1 mRNA, with the first effect seen by 1 h. These effects were abolished by actinomycin D, but not by cycloheximide, indicating a direct stimulatory effect on ENaC and sgk1 mRNA synthesis. The GC effect on transcription of ENaC-α mRNA was accompanied by a significant increase in ENaC-α protein levels. GC also stimulated ENaC-α, -β, and -γ and sgk1 mRNA expression in A549 cells, an alveolar type II cell line. To determine the biophysical properties of the Na + channel, single-channel currents were recorded from cell-attached H441 membranes. An Na + -selective channel with slow kinetics and a slope conductance of 10.8 pS was noted, properties similar to ENaC-α, -β, and -γ expressed in Xenopus laevis oocytes. These experiments indicate that amiloride-sensitive Na + transport is mediated through classic ENaC channels in human lung epithelia and that GC-regulated Na + transport is accompanied by increased transcription of each of the component subunits and sgk1.
Type of Medium:
Online Resource
ISSN:
1040-0605
,
1522-1504
DOI:
10.1152/ajplung.00085.2001
Language:
English
Publisher:
American Physiological Society
Publication Date:
2002
detail.hit.zdb_id:
1477300-4
SSG:
12
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