A regulated apical Na+ conductance in dexamethasone-treated H441 airway epithelial cells

S. J. Ramminger, K. Richard, S. K. Inglis, S. C. Land, R. E. Olver, S. M. Wilson

    Research output: Contribution to journalArticle

    35 Citations (Scopus)

    Abstract

    Treating H441 cells with dexamethasone raised the abundance of mRNA encoding the epithelial Na+ channel a- and -subunits and increased transepithelial ion transport (measured as short-circuit current, Isc) from <4 µA·cm–2 to 10–20 µA·cm–2. This dexamethasone-stimulated ion transport was blocked by amiloride analogs with a rank order of potency of benzamil = amiloride > EIPA and can thus be attributed to active Na+ absorption. Studies of apically permeabilized cells showed that this increased transport activity did not reflect a rise in Na+ pump capacity, whereas studies of basolateral permeabilized cells demonstrated that dexamethasone increased apical Na+ conductance (GNa) from a negligible value to 100–200 µS·cm–2. Experiments that explored the ionic selectivity of this dexamethasone-induced conductance showed that it was equally permeable to Na+ and Li+ and that the permeability to these cations was approximately fourfold greater than to K+. There was also a small permeability to N-methyl-D-glucammonium, a nominally impermeant cation. Forskolin, an agent that increases cellular cAMP content, caused an ~60% increase in Isc, and measurements made after these cells had been basolaterally permeabilized demonstrated that this response was associated with a rise in GNa. This cAMP-dependent control over GNa was disrupted by brefeldin A, an inhibitor of vesicular trafficking. Dexamethasone thus stimulates Na+ transport in H441 cells by evoking expression of an amiloride-sensitive apical conductance that displays moderate ionic selectivity and is subject to acute control via a cAMP-dependent pathway.
    Original languageEnglish
    Pages (from-to)L411-L419
    JournalAmerican Journal of Physiology: Lung Cellular and Molecular Physiology
    Volume287
    Issue number2
    Publication statusPublished - Aug 2004

    Fingerprint

    Dexamethasone
    Epithelial Cells
    Cations
    Permeability
    Epithelial Sodium Channels
    Brefeldin A
    Amiloride
    Ion Transport
    Colforsin
    Messenger RNA

    Keywords

    • Airway epithelium
    • Epithelial sodium channel
    • Ussing chambers
    • Glucocorticoids
    • Apical membrane

    Cite this

    Ramminger, S. J. ; Richard, K. ; Inglis, S. K. ; Land, S. C. ; Olver, R. E. ; Wilson, S. M. / A regulated apical Na+ conductance in dexamethasone-treated H441 airway epithelial cells. In: American Journal of Physiology: Lung Cellular and Molecular Physiology. 2004 ; Vol. 287, No. 2. pp. L411-L419.
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    A regulated apical Na+ conductance in dexamethasone-treated H441 airway epithelial cells. / Ramminger, S. J.; Richard, K.; Inglis, S. K.; Land, S. C.; Olver, R. E.; Wilson, S. M.

    In: American Journal of Physiology: Lung Cellular and Molecular Physiology, Vol. 287, No. 2, 08.2004, p. L411-L419.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - A regulated apical Na+ conductance in dexamethasone-treated H441 airway epithelial cells

    AU - Ramminger, S. J.

    AU - Richard, K.

    AU - Inglis, S. K.

    AU - Land, S. C.

    AU - Olver, R. E.

    AU - Wilson, S. M.

    N1 - dc.publisher: American Physiological Society The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. dc.description.sponsorship: Wellcome Trust Tenovus Scotland

    PY - 2004/8

    Y1 - 2004/8

    N2 - Treating H441 cells with dexamethasone raised the abundance of mRNA encoding the epithelial Na+ channel a- and -subunits and increased transepithelial ion transport (measured as short-circuit current, Isc) from <4 µA·cm–2 to 10–20 µA·cm–2. This dexamethasone-stimulated ion transport was blocked by amiloride analogs with a rank order of potency of benzamil = amiloride > EIPA and can thus be attributed to active Na+ absorption. Studies of apically permeabilized cells showed that this increased transport activity did not reflect a rise in Na+ pump capacity, whereas studies of basolateral permeabilized cells demonstrated that dexamethasone increased apical Na+ conductance (GNa) from a negligible value to 100–200 µS·cm–2. Experiments that explored the ionic selectivity of this dexamethasone-induced conductance showed that it was equally permeable to Na+ and Li+ and that the permeability to these cations was approximately fourfold greater than to K+. There was also a small permeability to N-methyl-D-glucammonium, a nominally impermeant cation. Forskolin, an agent that increases cellular cAMP content, caused an ~60% increase in Isc, and measurements made after these cells had been basolaterally permeabilized demonstrated that this response was associated with a rise in GNa. This cAMP-dependent control over GNa was disrupted by brefeldin A, an inhibitor of vesicular trafficking. Dexamethasone thus stimulates Na+ transport in H441 cells by evoking expression of an amiloride-sensitive apical conductance that displays moderate ionic selectivity and is subject to acute control via a cAMP-dependent pathway.

    AB - Treating H441 cells with dexamethasone raised the abundance of mRNA encoding the epithelial Na+ channel a- and -subunits and increased transepithelial ion transport (measured as short-circuit current, Isc) from <4 µA·cm–2 to 10–20 µA·cm–2. This dexamethasone-stimulated ion transport was blocked by amiloride analogs with a rank order of potency of benzamil = amiloride > EIPA and can thus be attributed to active Na+ absorption. Studies of apically permeabilized cells showed that this increased transport activity did not reflect a rise in Na+ pump capacity, whereas studies of basolateral permeabilized cells demonstrated that dexamethasone increased apical Na+ conductance (GNa) from a negligible value to 100–200 µS·cm–2. Experiments that explored the ionic selectivity of this dexamethasone-induced conductance showed that it was equally permeable to Na+ and Li+ and that the permeability to these cations was approximately fourfold greater than to K+. There was also a small permeability to N-methyl-D-glucammonium, a nominally impermeant cation. Forskolin, an agent that increases cellular cAMP content, caused an ~60% increase in Isc, and measurements made after these cells had been basolaterally permeabilized demonstrated that this response was associated with a rise in GNa. This cAMP-dependent control over GNa was disrupted by brefeldin A, an inhibitor of vesicular trafficking. Dexamethasone thus stimulates Na+ transport in H441 cells by evoking expression of an amiloride-sensitive apical conductance that displays moderate ionic selectivity and is subject to acute control via a cAMP-dependent pathway.

    KW - Airway epithelium

    KW - Epithelial sodium channel

    KW - Ussing chambers

    KW - Glucocorticoids

    KW - Apical membrane

    M3 - Article

    VL - 287

    SP - L411-L419

    JO - American Journal of Physiology: Lung Cellular and Molecular Physiology

    JF - American Journal of Physiology: Lung Cellular and Molecular Physiology

    SN - 1040-0605

    IS - 2

    ER -