Sodium transport and intracellular sodium activity in cultured human nasal epithelium.
Human airway epithelia are predominantly Na(+)-absorbing epithelia. To investigate the mechanisms for Na+ absorption across airway epithelia, the driving forces and paths for Na+ translocation across each membrane were examined with double-barreled Na(+)-selective microelectrodes in cultured human nasal epithelium (HNE). Under control conditions, intracellular Na+ activity (acNa) was 23 +/- 1 mM (n = 44 preparations, 393 impalements). Amiloride (10(-4) M) hyperpolarized the apical membrane and increased the fractional apical membrane resistance but did not affect acNa. Exposure to Na(+)-free luminal solution induced bioelectric responses similar to amiloride but also reduced acNa to 8 +/- 1 mM. Reduction of luminal Na+ concentration ([Na+]) in the presence of amiloride also reduced acNa without further changes in bioelectric parameters. Reduction of serosal [Na+] decreased aNac, a response blocked by bumetanide (10(-4) M). Ouabain (10(-4) M, serosal) led to a reduction in equivalent short-circuit current (Ieq) and increase in acNa. We conclude that 1) acNa is higher in HNE than in most mammalian epithelial cells, 2) the apical membrane expresses a conductive Na+ path, and 3) the basolateral membrane transports Na+ via the Na(+)-K(+)-adenosinetriphosphatase and a Na(+)-K(+)-2Cl- cotransport system.
Willumsen
N J
NJ
Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill 27514.
Boucher
R C
RC
D000293:Adolescent; D000328:Adult; D000584:Amiloride / Q000494:pharmacology; D000666:Amphotericin B / Q000494:pharmacology; D001692:Biological Transport; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D004594:Electrophysiology; D005260:Female; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009297:Nasal Mucosa / Q000378:metabolism*; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D012704:Serous Membrane / Q000378:metabolism; D012964:Sodium / Q000493:pharmacokinetics* / Q000494:pharmacology
D002034:Bumetanide; D010042:Ouabain; D000584:Amiloride; D000666:Amphotericin B; D012964:Sodium