Cellular Cl- transport in cultured cystic fibrosis airway epithelium.
Cultured human nasal epithelia derived from cystic fibrosis (CF) patients were studied with double-barreled, Cl- -selective microelectrodes to measure membrane potentials and intracellular Cl- activity (aClc). The aClc of CF cultures was 46.5 +/- 2.5 mM (n = 28), a value not significantly different from aClc of normal human nasal cells. Reduction of the luminal [Cl-] from 120 to 3 mM failed to reveal any apical Cl- permeability (conductive or nonconductive) in CF cultures. Bumetanide (10(-4) M, serosal) led to a 10 mM decrease in aClc without affecting the electrical parameters of the cells. Reduction of serosal [Cl-] led to a marked decrease in aClc (from 58.0 +/- 6.7 to 26.8 +/- 2.9 mM) that could partly be blocked by bumetanide. Reduction of serosal [Cl-] led to a rapid depolarization (5.4 +/- 0.7 mV) of the basolateral membrane potential (Vb), a decrease of the fractional apical membrane resistance (0.03 +/- 0.01), and an increase (34 +/- omega.cm2) in the transepithelial resistance (Rt). We conclude that 1) the apical membrane of CF airway epithelia is impermeable to Cl-, and 2) Cl- transport across the basolateral membrane occurs mainly through a bumetanide-inhibitable cotransport system but also through a Cl- conductance, neither of which appears to be affected by CF.
Willumsen
N J
NJ
Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill 27514.
Davis
C W
CW
Boucher
R C
RC
D000293:Adolescent; D000328:Adult; D000584:Amiloride / Q000494:pharmacology; D001692:Biological Transport; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D002712:Chlorides / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D009297:Nasal Mucosa / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism
D002712:Chlorides; D002034:Bumetanide; D000584:Amiloride; D011188:Potassium