NMR measurements of the diffusional permeability of water in cultured colonic epithelial cancer cells

The water residence time and diffusional water permeability in colonic epithelial T84 cancer cells was measured using H-1 NMR spectroscopy; the values estimated were 35.2 +/- 2.8 ms and (7.4 +/- 0.6) x 10(-3) cm s(-1), respectively. Water permeability was inhibited to similar to 10% of its original value by the mercurial diuretic, p-chloromercuribenzenesulforrate (PCMBS; I mM), and fully restored by dithiothreitol (DTT; I mM). The permeability was also inhibited reversibly to similar to 55%, by extracellular glibenclamide (I mM), an inhibitor of some ATP-binding cassette (ABC) transporters, including the cystic fibrosis transmembrane conductance regulator (CFTR). Addition of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IMBX 0.1 - 1 mM) and the adenylate cyclase activator, forskolin (0.1 - 1 mM) did not alter water permeability. It is concluded that in T84 cells water diffuses through the membrane lipid bilayer and via channels that are inhibited by PCMBS, including the channels that are known to be inhibited by glibenclamide. (c) 2005 International Federation for Cell Biology. Published by Elsevier Ltd. All rights reserved.