Abstract
H441 cells, a bronchiolar epithelial cell line, develop a cAMP-regulated benzamil-sensitive Na+ transport pathway on permeable supports (Itani OA, Auerbach SD, Husted RF, Volk KA, Ageloff S, Knepper MA, Stokes JB, Thomas CP. Am J Physiol Lung Cell Mol Physiol 282: L631-L641, 2002). To understand the molecular basis for the stimulation of Na+ transport, we delineated the role of specific intracellular pathways and examined the effect of cAMP on alphabetagamma-epithelial Na+ channel (ENaC) and sgk1 expression. Na+ transport increases within 5 min of cAMP stimulation and is sustained for >24 h. The sustained effect of cAMP on Na+ transport is abolished by LY-294002, an inhibitor of phosphatidylinositol 3-kinase, by H89, an inhibitor of PKA, or by SB-202190, an inhibitor of p38 MAP kinase. The sustained effect of cAMP was associated with increases in alpha-ENaC mRNA and protein but without a detectable increase in betagamma-ENaC and sgk1. The early effect of cAMP on Na+ transport is brefeldin sensitive and is mediated via PKA. These results are consistent with a model where the early effect of cAMP is to increase trafficking of Na+ channels to the apical cell surface whereas the sustained effect requires the synthesis of alpha-ENaC.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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1-Methyl-3-isobutylxanthine / pharmacology
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Biological Transport / drug effects
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Cell Line
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Chromones / pharmacology
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Colforsin / pharmacology
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Cyclic AMP / physiology*
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Cyclic AMP-Dependent Protein Kinases / metabolism*
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Dexamethasone / pharmacology
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Enzyme Inhibitors / pharmacology
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Epithelial Sodium Channels
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Humans
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Immediate-Early Proteins
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Kinetics
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Lung
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Morpholines / pharmacology
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Nuclear Proteins / metabolism*
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Phosphatidylinositol 3-Kinases / metabolism*
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Protein Serine-Threonine Kinases / metabolism*
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Respiratory Mucosa / drug effects
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Respiratory Mucosa / physiology*
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Sodium / metabolism*
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Sodium Channels / physiology
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p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors
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p38 Mitogen-Activated Protein Kinases / metabolism
Substances
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Chromones
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Enzyme Inhibitors
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Epithelial Sodium Channels
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Immediate-Early Proteins
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Morpholines
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Nuclear Proteins
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Sodium Channels
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Colforsin
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Dexamethasone
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Sodium
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Cyclic AMP
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Protein Serine-Threonine Kinases
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serum-glucocorticoid regulated kinase
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Cyclic AMP-Dependent Protein Kinases
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p38 Mitogen-Activated Protein Kinases
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1-Methyl-3-isobutylxanthine