Evidence for apical sodium channels in frog lung epithelial cells

1989 ◽  
Vol 256 (4) ◽  
pp. C764-C771 ◽  
Author(s):  
H. Fischer ◽  
W. Van Driessche ◽  
W. Clauss
Keyword(s):  
Epithelial Cells ◽  
Short Circuit ◽  
Lung Epithelial Cells ◽  
Power Density Spectrum ◽  
Fluctuation Analysis ◽  
Na Transport ◽  
Density Spectrum ◽  
Isolated Lung ◽  
Lung Epithelial ◽  
Single Channel Currents

To reveal the mechanism of Na+ transport across Xenopus lung epithelium, we recorded short-circuit current (Isc), transepithelial resistance (Rt), and current noise spectra while the isolated lung tissues were mounted in an Ussing-type chamber. Mean values of Isc and Rt obtained while the tissue was bilaterally incubated with NaCl-Ringer solution were Isc = 11.57 +/- 1.19 microA.cm-2 and Rt = 0.82 +/- 0.07 k omega.cm2. Amiloride added to the mucosal (apical) side depressed Isc by 61 to 99%. Ouabain abolished Isc totally when added to the basolateral compartment. Adenosine 3',5'-cyclic monophosphate (cAMP), epinephrine, and a variety of other compounds did not alter Isc significantly. Transepithelial depolarization with serosal KCl solution reduced Isc to 6.22 +/- 1.37 microA.cm-2. Amiloride-sensitive current and the kinetics of amiloride interaction were not significantly affected by depolarization. Fluctuation analysis of Isc in the presence of amiloride revealed a Lorentzian component in the power density spectrum indicating apical Na+ channels. Assuming pseudo-first order kinetics, we calculated single channel currents (iNa) and channel density (M): iNa = 0.29 +/- 0.04 pA and M = 0.24 +/- 0.04 micron 2. Our results show that the route for Na+ transport through lung epithelial cells follows the classical Koefoed-Johnson-Ussing model for tight epithelia.

Inhibition of amiloride-sensitive sodium-channel activity in distal lung epithelial cells by nitric oxide

1998 ◽  
Vol 274 (3) ◽  
pp. L378-L387 ◽  
Author(s):  
Jin Wen Ding ◽  
John Dickie ◽  
Hugh O’Brodovich ◽  
Yutaka Shintani ◽  
Bijan Rafii ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Epithelial Cells ◽  
Cell Function ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Lung Epithelial Cells ◽  
Flufenamic Acid ◽  
Activated Macrophages ◽  
Lung Epithelial ◽  
Distal Lung

Distal lung epithelial cells (DLECs) play an active role in fluid clearance from the alveolus by virtue of their ability to actively transport Na+ from the alveolus to the interstitial space. The present study evaluated the ability of activated macrophages to modulate the bioelectric properties of DLECs. Low numbers of lipopolysaccharide (LPS)-treated macrophages were able to significantly reduce amiloride-sensitive short-circuit current ( I sc) without affecting total I sc or monolayer resistance. This was associated with a rise in the flufenamic acid-sensitive component of the I sc. The effect was reversed by the addition of N-monomethyl-l-arginine to the medium, implying a role for nitric oxide. We hypothesized that macrophages exerted their effect by expressing inducible nitric oxide synthase (iNOS) in DLECs. The products of LPS-treated macrophages increased the levels of iNOS protein and mRNA transcripts in DLECs as well as causing a rise in iNOS activity. Immunofluorescence microscopy of LPS-stimulated macrophage-DLEC cocultures with anti-nitrotyrosine antibodies provided evidence for the generation of peroxynitrite in macrophages but not in DLECs. These data indicate that activated macrophages in the lung may contribute to impaired resolution of acute respiratory distress syndrome and suggest a novel mechanism whereby nitric oxide might alter cell function by altering its ion-transporting phenotype.

Long-term terbutaline exposure stimulates α1-Na+-K+-ATPase expression at posttranscriptional level in rat fetal distal lung epithelial cells

2010 ◽  
Vol 298 (1) ◽  
pp. L96-L104 ◽  
Author(s):  
Muhammad S. Rahman ◽  
Shephali Gandhi ◽  
Gail Otulakowski ◽  
Wenming Duan ◽  
Aparna Sarangapani ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Atpase Activity ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Lung Epithelial Cells ◽  
Intracellular Camp ◽  
Adult Type ◽  
Lung Epithelial ◽  
Distal Lung

Transepithelial Na+ transport through epithelial Na+ channels (ENaC) on the apical membrane and Na+-K+-ATPase activity on the basolateral membrane of distal lung epithelial cells are critical for alveolar fluid clearance. Acute exposure to β-adrenergic agonists stimulates lung fluid clearance by increasing Na+ transport. We investigated the effects of chronic exposure to the β2-adrenergic agonist terbutaline on the transepithelial Na+ transport in rat fetal distal lung epithelia (FDLE). FDLE monolayers exposed to 10−4 M terbutaline for 48 h had significantly increased propanolol-blockable transepithelial total and amiloride-sensitive short-circuit current ( Isc); however, when these chronically exposed monolayers were acutely exposed to additional β-agonists and intracellular cAMP upregulators, there was no further increase in Isc. Monolayers exposed to terbutaline for >48 h had Isc similar to control cells. Ouabain-sensitive Na+-K+-ATPase activity was increased in 48-h terbutaline-exposed FDLE whose apical membranes were permeabilized with nystatin. In contrast, terbutaline did not increase amiloride-sensitive apical membrane Isc in FDLE whose basolateral membranes were permeabilized with nystatin. Terbutaline treatment did not affect α-, β-, or γ-ENaC mRNA or α-ENaC protein steady-state levels, but increased total cellular levels and rate of synthesis of α1-Na+-K+-ATPase protein in FDLE in the absence of any change in α1-Na+-K+-ATPase mRNA. Total cellular β1-Na+-K+-ATPase mRNA and protein levels were not affected by terbutaline. These data suggest that FDLE have different responses from adult type II epithelial cells when chronically exposed to terbutaline, and their increased transepithelial Na+ transport occurs via a posttranscriptional increase in α1-Na+-K+-ATPase expression.

scholarly journals The gasotransmitter hydrogen sulphide decreases Na + transport across lung epithelial cells

2012 ◽  
Vol 26 (S1) ◽  
Author(s):  
Mike Althaus ◽  
Kevin Douglas Urness ◽  
Wolfgang Clauss ◽  
Deborah L Baines ◽  
Martin Fronius
Keyword(s):  
Epithelial Cells ◽  
Hydrogen Sulphide ◽  
Lung Epithelial Cells ◽  
Na Transport ◽  
Lung Epithelial

scholarly journals Oxygen‐evoked Na + transport in rat fetal distal lung epithelial cells

2001 ◽  
Vol 532 (1) ◽  
pp. 105-113 ◽  
Author(s):  
D. L. Baines ◽  
S. J. Ramminger ◽  
A. Collett ◽  
J. J. E. Haddad ◽  
O. G. Best ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Lung Epithelial Cells ◽  
Na Transport ◽  
Lung Epithelial ◽  
Distal Lung

Developmental differences in rabbit lung epithelial cell Na(+)-K(+)-ATPase

1990 ◽  
Vol 259 (6) ◽  
pp. L481-L487 ◽  
Author(s):  
D. L. Chapman ◽  
J. H. Widdicombe ◽  
R. D. Bland
Keyword(s):  
Epithelial Cells ◽  
Turnover Rate ◽  
Developmental Differences ◽  
Lung Epithelial Cells ◽  
Rabbit Lung ◽  
Fetal Cells ◽  
Na Pump ◽  
Isolated Lung ◽  
Lung Epithelial ◽  
Adult Cells

Previous studies showed that ouabain-sensitive rubidium (86Rb+) uptake by rabbit lung epithelial cells increases at birth, followed by a more gradual postnatal increase, reaching adult values by age 30 days. To see whether these changes in ouabain-sensitive cation transport were the result of changes in Na+ pump number or turnover rate, we measured binding of [3H]ouabain and ouabain-sensitive 86Rb+ uptake by freshly isolated lung epithelial cells harvested from near-term fetal, newborn, and adult rabbits. Ouabain-sensitive 86Rb+ uptake by fetal cells was 1/4 that of newborn cells and 1/10 that of adult cells. The maximal number of ouabain binding sites (Umax) was the same for fetal and newborn cells but almost threefold greater for adult cells. Na+ pump turnover rate, determined from ouabain-sensitive 86Rb+ uptake and Umax, was four times greater in newborn and adult cells than it was in fetal cells. Thus the increase in 86Rb+ uptake at birth could be explained by an increase in Na(+)-K(+)-adenosinetriphosphatase (ATPase) turnover rate, whereas the postnatal increase in 86Rb+ uptake could be accounted for by an increase in the amount of Na(+)-K(+)-ATPase per cell.

pH-regulated chloride secretion in fetal lung epithelia

2000 ◽  
Vol 278 (6) ◽  
pp. L1248-L1255 ◽  
Author(s):  
Carol J. Blaisdell ◽  
Rebecca D. Edmonds ◽  
Xi-Tao Wang ◽  
Sandra Guggino ◽  
Pamela L. Zeitlin
Keyword(s):  
Epithelial Cells ◽  
Short Circuit ◽  
Fetal Lung ◽  
Chloride Secretion ◽  
Lung Epithelial Cells ◽  
Apical Surface ◽  
Ussing Chambers ◽  
Lung Fluid ◽  
Lung Epithelial ◽  
Distal Lung

The fetal lung actively transports chloride across the airway epithelium. ClC-2, a pH-activated chloride channel, is highly expressed in the fetal lung and is located on the apical surface of the developing respiratory epithelium. Our goal was to determine whether acidic pH could stimulate chloride secretion in fetal rat distal lung epithelial cells mounted in Ussing chambers. A series of acidic solutions stimulated equivalent short-circuit current ( I eq) from a baseline of 28 ± 4.8 (pH 7.4) to 70 ± 5 (pH 6.2), 114 ± 12.8 (pH 5.0), and 164 ± 19.2 (pH 3.8) μA/cm2. These changes in I eq were inhibited by 1 mM cadmium chloride and did not result in large changes in [3H]mannitol paracellular flux. Immunofluorescent detection by confocal microscopy revealed that ClC-2 is expressed along the luminal surface of polarized fetal distal lung epithelial cells. These data suggest that the acidic environment of the fetal lung fluid could activate chloride channels contributing to fetal lung fluid production and that the changes in I eqseen in these Ussing studies may be due to stimulation of ClC-2.

Fetal lung cell-derived matrix alters distal lung epithelial ion transport

1995 ◽  
Vol 268 (5) ◽  
pp. L762-L771 ◽  
Author(s):  
O. M. Pitkanen ◽  
A. K. Tanswell ◽  
H. M. O'Brodovich
Keyword(s):  
Epithelial Cells ◽  
Ion Transport ◽  
Short Circuit ◽  
Alveolar Epithelial Cells ◽  
Lung Epithelial Cells ◽  
Bathing Solution ◽  
Type I ◽  
Ussing Chambers ◽  
Lung Epithelial ◽  
Distal Lung

Extracellular matrix (ECM) synthesized by the fetal mesenchymal cells provides a supporting structure for the growing airways and is important for airway branching and in the differentiation of the primitive epithelium. We studied whether ECM, in addition to its structural role in lung interstitium, influences the ion transport of rat fetal distal lung epithelial cells (FDLE). FDLE monolayers were cultured on two different fetal mixed lung cell (MLC)-derived matrix preparations and studied in Ussing chambers. FDLE on MLC matrix had an increased resting equivalent short-circuit current (Ieq). Amiloride (10(-4) M apically) decreased the Ieq significantly in all the FDLE monolayers. The residual Ieq was significantly larger in FDLE grown on MLC matrix (increased by 150 and 80% under baseline and beta 2-agonist-stimulated conditions, respectively) than on control filters and filters coated with type I collagen, and type IV collagen, laminin, or fibronectin. The matrix produced by MLC isolated at an earlier gestational stage decreased the FDLE's sensitivity to amiloride. The increased amiloride-insensitive Ieq was only modestly affected by the Na+/K+/Cl- cotransport inhibitor bumetanide (10(-4) M basally) but was abolished when the [Cl-] of the bathing solution was reduced to 10 mM. These observations demonstrated that MLC elaborated ECM is able to change the nature of the ion transport of FDLE. ECM may be an important factor governing the ion transporting phenotype of fetal type II alveolar epithelial cells.

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