Alpha-adrenergic regulation of Na-Cl cotransport in human airway epithelium.
The demonstration of abnormal beta-adrenergic and cAMP-modulated apical Cl- channels in cystic fibrosis (CF) airway epithelial cells suggests that other transporters, which are required for Cl- secretion, may also be abnormally regulated. A basolateral cotransporter was investigated by determining the initial rate of 36Cl efflux from cells isolated from CF nasal polyps or trachea and non-CF trachea. Cells were preequilibrated with radioactive tracer at 25 degrees C, and tracer transport was initiated by 10-fold dilution of an aliquot of cells in radioisotope-free medium. The initial rate of Cl transport was calculated from the linear portion of the efflux curves. In CF and non-CF cells, base-line Cl- transport was not blocked by furosemide but was stimulated twofold by l-epinephrine in Ca2+-deficient and Ca2+-replete transport medium. In both types of cells, furosemide blocked 70 and 77%, respectively, of the stimulated Cl- transport. Prazosin, an alpha 1-adrenergic antagonist, blocked the effects of l-epinephrine and methoxamine, an alpha 1-adrenergic agonist, stimulated prazosin- and furosemide-sensitive Cl transport. Ionomycin mimicked the effects of l-epinephrine. l-Isoproterenol, a beta-adrenergic agonist, did not affect Cl transport. The results of this study indicate an alpha 1-adrenergic stimulation of furosemide-sensitive Cl transport in human airway epithelium that functions normally in CF airway epithelial cells. The transport mechanism is probably a Na-Cl or Na-K-2Cl cotransport located in the basolateral membrane and requires elevated intracellular Ca2+ for activation.
Liedtke
C M
CM
Department of Pediatrics, Rainbow Babies and Children Hospital, Cleveland, Ohio 44106.
D002352:Carrier Proteins / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology*; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005665:Furosemide / Q000494:pharmacology; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D008729:Methoxamine / Q000494:pharmacology*; D009298:Nasal Polyps / Q000378:metabolism*; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D049992:Sodium Chloride Symporters; D027981:Symporters; D014132:Trachea / Q000378:metabolism*
D002352:Carrier Proteins; D002712:Chlorides; D011942:Receptors, Adrenergic, alpha; D049992:Sodium Chloride Symporters; D027981:Symporters; D005665:Furosemide; D008729:Methoxamine; D007545:Isoproterenol; D011224:Prazosin; D004837:Epinephrine