Open AccessHypotonic Shock Modulates Na+ Current via a Cl- and Ca2+/Calmodulin Dependent Mechanism in Alveolar Epithelial Cells
Author(s) -
André Dagenais,
Marie-Claude Tessier,
Sabina Tatur,
Emmanuelle Brochiero,
Ryszard Grygorczyk,
Yves Berthiaume
Publication year - 2013
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0074565
Subject(s) - epithelial sodium channel , amiloride , apyrase , apical membrane , ion transporter , chemistry , tonicity , transepithelial potential difference , transcellular , calmodulin , microbiology and biotechnology , medicine , biophysics , endocrinology , biology , sodium , biochemistry , extracellular , membrane , organic chemistry , enzyme
Alveolar epithelial cells are involved in Na + absorption via the epithelial Na + channel (ENaC), an important process for maintaining an appropriate volume of liquid lining the respiratory epithelium and for lung oedema clearance. Here, we investigated how a 20% hypotonic shock modulates the ionic current in these cells. Polarized alveolar epithelial cells isolated from rat lungs were cultured on permeant filters and their electrophysiological properties recorded. A 20% bilateral hypotonic shock induced an immediate, but transient 52% rise in total transepithelial current and a 67% increase in the amiloride-sensitive current mediated by ENaC. Amiloride pre-treatment decreased the current rise after hypotonic shock, showing that ENaC current is involved in this response. Since Cl - transport is modulated by hypotonic shock, its contribution to the basal and hypotonic-induced transepithelial current was also assessed. Apical NPPB, a broad Cl - channel inhibitor and basolateral DIOA a potassium chloride co-transporter (KCC) inhibitor reduced the total and ENaC currents, showing that transcellular Cl - transport plays a major role in that process. During hypotonic shock, a basolateral Cl - influx, partly inhibited by NPPB is essential for the hypotonic-induced current rise. Hypotonic shock promoted apical ATP secretion and increased intracellular Ca 2+ . While apyrase, an ATP scavenger, did not inhibit the hypotonic shock current response, W7 a calmodulin antagonist completely prevented the hypotonic current rise. These results indicate that a basolateral Cl - influx as well as Ca 2+ /calmodulin, but not ATP, are involved in the acute transepithelial current rise elicited by hypotonic shock.