Sodium transport and intracellular sodium activity in cultured human nasal epithelium
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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 wereexamined 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.
Original language | English |
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Journal | American Journal of Physiology: Cell Physiology |
Volume | 261 |
Issue number | 2 |
Pages (from-to) | C319-C331 |
ISSN | 0363-6143 |
Publication status | Published - 1991 |
ID: 304831