title: Deuterium oxide dilution: a novel method to study apical water layers and transepithelial water transport.
abstract: Lung epithelia regulate the water flux between gas filled airways and the interstitial compartment in order to maintain organ function. Current methodology to assess transepithelial water transport is limited. We present a D2O dilution method to quantify submicroliter volumes of aqueous solutions on epithelial cell layers. Evaluating D2O/H2O mixtures using mid-infrared (2-25 μm) attenuated total reflection (ATR) spectroscopy, with a resolution of 0.06% vol/vol change, corresponding to 24 nL, was achieved. Using this method, we demonstrate that water transport across NCI-H441 lung epithelial cell layers and apical surface liquid (ASL) volumes are coupled to dexamethasone dependent amiloride-sensitive ion transport. However, contrary to current dogma, electrogenic transport is not rate-limiting for water transport. This clearly indicates the need to directly assess net water rather than ion transport across epithelial cell layers. The presented D2O dilution method enables such direct and quick quantification of transepithelial water transport with high resolution.
authors.affiliation: Institute of Analytical and Bioanalytical Chemistry, University of Ulm, Ulm, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Neubauer
authors.forename: Jonas
authors.initials: J
authors.lastname: Korbmacher
authors.forename: Manfred
authors.initials: M
authors.lastname: Frick
authors.forename: Johanna
authors.initials: J
authors.lastname: Kiss
authors.forename: Melanie
authors.initials: M
authors.lastname: Timmler
authors.forename: Paul
authors.initials: P
authors.lastname: Dietl
authors.forename: Oliver H
authors.initials: OH
authors.lastname: Wittekindt
authors.forename: Boris
authors.initials: B
authors.lastname: Mizaikoff
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D001692:Biological Transport; D017666:Deuterium Oxide / Q000032:analysis; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D007201:Indicator Dilution Techniques; D008168:Lung / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water; D017666:Deuterium Oxide