Enhanced osmotic water permeability has been observed in Xenopus oocytes expressing
cystic fibrosis transmembrane conductance regulator (CFTR) protein. Subsequent studies
have shown that CFTR activates an endogenous water permeability in oocytes, but that
CFTR itself is not the water channel. Here, we show CFTR-dependent activation of
endogenous water permeability in normal but not in cystic fibrosis human airway epithelial
cells. Cell volume was measured by novel confocal xz laser scanning microscopy. Glycerol …