Transcellular sodium transport in cultured cystic fibrosis human nasal epithelium

Am J Physiol. 1991 Aug;261(2 Pt 1):C332-41. doi: 10.1152/ajpcell.1991.261.2.C332.


Cystic fibrosis (CF) airway epithelia exhibit raised transepithelial Na+ transport rates, as determined by open-circuit isotope fluxes and estimates of the amiloride-sensitive equivalent short-circuit current (Ieq). To study the contribution of apical and basolateral membrane paths to raised Na+ transport in CF, CF nasal epithelial cultures were studied with double-barreled Na(+)-selective microelectrodes and the Ussing chamber technique. Intracellular Na+ activity (acNa) was 24.1 +/- 1.5 mM (n = 36), a value similar to acNa of normal nasal epithelial cells. Reduction of luminal [Na+] to 3 mM abolished Ieq and reduced acNa. Amiloride (10(-4) M) abolished Ieq but increased acNa from 20 +/- 2 to 36 +/- 7 mM (n = 10). Amiloride-induced increase in acNa was not affected by serosal [Na+] reduction but was blocked by preexposure to reduced luminal [Na+]. Amphotericin B increased Ieq during amiloride exposure, indicating that amiloride did not inhibit NA(+)-K(+)-ATPase. Ouabain abolished Ieq and slowly raised acNa. Reduction of serosal [Na+] led to a decrease in acNa that was blocked by bumetanide. It is concluded that 1) CF airway epithelia exhibit an increased apical membrane Na+ permeability, 2) acNa is regulated to a normal level in CF cells despite increased transcellular Na+ fluxes, 3) the abnormal increase in acNa in response to amiloride is dependent on luminal Na+, 4) Na+ is transported across the basolateral membrane by a bumetanide-sensitive cotransport mechanism, and 5) ouabain inhibits the basolateral Na(+)-K(+)-ATPase, causing slow dissipation of the chemical and electrical gradients across the cell membranes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Amiloride / pharmacology
  • Amphotericin B / pharmacology
  • Biological Transport
  • Bumetanide / pharmacology
  • Cells, Cultured
  • Child
  • Cystic Fibrosis / metabolism*
  • Electrophysiology
  • Epithelium
  • Female
  • Humans
  • Male
  • Nasal Mucosa / metabolism*
  • Osmolar Concentration
  • Ouabain / pharmacology
  • Sodium / pharmacokinetics*
  • Sodium / pharmacology


  • Bumetanide
  • Ouabain
  • Amiloride
  • Amphotericin B
  • Sodium