Wild type but not deltaF508 CFTR inhibits Na+ conductance when coexpressed in Xenopus oocytes

FEBS Lett. 1996 Feb 26;381(1-2):47-52. doi: 10.1016/0014-5793(96)00079-8.


Airway epithelial cells bearing mutations of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) possess an increased Na+ conductance along with their well described defect of cAMP dependent Cl- conductance. Currently it is not clear, how this occurs, and whether it is due to a CFTR control of epithelial Na+ conductances which might be defective in CF patients. In the present study, we have tried to identify possible interactions between both CFTR and the epithelial Na+ conductance by overexpressing respective cRNAs in Xenopus oocytes. The expression of all three (alpha, beta, gamma) subunits of the rat epithelial Na+ channel (rENaC) and wild type (wt) CFTR resulted in the expected amiloride sensitive Na+ and IBMX (1 mmol/l) activated Cl- currents, respectively. The amiloride sensitive Na+ conductance was, however, inhibited when the wt-CFTR Cl- conductance was activated by phosphodiesterase inhibition (IBMX). In contrast, IBMX had no such effect in deltaF508 and Na+ channels coexpressing oocytes. These results suggest that wt-CFTR, but not deltaF508-CFTR, is a cAMP dependent downregulator of epithelial Na+ channels. This may explain the higher Na+ conductance observed in airway epithelial cells of CF patients.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • Amiloride / pharmacology
  • Animals
  • Cell Membrane / drug effects
  • Cell Membrane / physiology
  • Chlorides / metabolism*
  • Cloning, Molecular
  • Cystic Fibrosis Transmembrane Conductance Regulator / biosynthesis
  • Cystic Fibrosis Transmembrane Conductance Regulator / physiology*
  • Female
  • Meglumine / pharmacology
  • Membrane Potentials / drug effects
  • Mutagenesis, Site-Directed
  • Oocytes / physiology*
  • Patch-Clamp Techniques
  • RNA, Complementary
  • Rats
  • Sodium / metabolism*
  • Sodium Channels / biosynthesis
  • Sodium Channels / physiology*
  • Xenopus laevis


  • Chlorides
  • RNA, Complementary
  • Sodium Channels
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • Meglumine
  • Amiloride
  • Sodium
  • 1-Methyl-3-isobutylxanthine