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. 
