Increased resistance of cystic fibrosis fibroblasts to ouabain toxicity.

Diploid skin fibroblasts derived from several unrelated patients with cystic fibrosis (CF) were tested for resistance to the cytotoxic effects of ouabain in comparison with cells from normal individuals. Cells from CF and normal individuals were plated at low density and exposed to ouabain at different concentrations for 24 hr. Dose-response curves showed that CF cells survived significantly better than did normal cells at all ouabain concentrations from 0.1 nM to 1 micronM in potassium-deficient medium. In medium containing the usual amount of potassium (6.25 mM), survival of the CF cells exposed to ouabain was decreased to that of the normal cells. If the glucose concentration of the potassium-deficient medium was decreased to 10% of the usual amount, the resistance of the CF cells to ouabain disappeared and their survival was identical to that of the normal cells. These findings may be useful in understanding the biochemical basis of CG and its clinical manifestations.