Chloride and potassium channels in cystic fibrosis airway epithelia.
Cystic fibrosis, the most common lethal genetic disease in Caucasians, is characterized by a decreased permeability in sweat gland duct and airway epithelia. In sweat duct epithelium, a decreased Cl- permeability accounts for the abnormally increased salt content of sweat. In airway epithelia a decreased Cl- permeability, and possibly increased sodium absorption, may account for the abnormal respiratory tract fluid. The Cl- impermeability has been localized to the apical membrane of cystic fibrosis airway epithelial cells. The finding that hormonally regulated Cl- channels make the apical membrane Cl- permeable in normal airway epithelial cells suggested abnormal Cl- channel function in cystic fibrosis. Here we report that excised, cell-free patches of membrane from cystic fibrosis epithelial cells contain Cl- channels that have the same conductive properties as Cl- channels from normal cells. However, Cl- channels from cystic fibrosis cells did not open when they were attached to the cell. These findings suggest defective regulation of Cl- channels in cystic fibrosis epithelia; to begin to address this issue, we performed two studies. First, we found that isoprenaline, which stimulates Cl- secretion, increases cellular levels of cyclic AMP in a similar manner in cystic fibrosis and non-cystic fibrosis epithelial cells. Second, we show that adrenergic agonists open calcium-activated potassium channels, indirectly suggesting that calcium-dependent stimulus-response coupling is intact in cystic fibrosis. These data suggest defective regulation of Cl- channels at a site distal to cAMP accumulation.
D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology; D003550:Cystic Fibrosis / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D010539:Permeability; D011188:Potassium / Q000378:metabolism*; D013566:Sympathomimetics / Q000494:pharmacology; D014132:Trachea / Q000378:metabolism*
D002712:Chlorides; D007473:Ion Channels; D013566:Sympathomimetics; D000242:Cyclic AMP; D011188:Potassium; D002118:Calcium