Letter: Na+ transport defect in cystic fibrosis.

Using the technique of 3H-ouabain binding to isolate cells Quissell and Pitot 
concluded that the Na+-K+ ATPase functions normally in fibroblasts from cystic 
fibrosis patients. However this finding may not be very relevant to 
the Na+ transport defect occurring in this genetic disease. The Na+ 
transport abnormality in cystic fibrosis seems to be confined to exocrine 
glands. It is unknown at present whether the defect resides in 
an active or passive transport step of the cation. At least 
with isolated sweat gland tissue and erythrocytes from cystic fibrosis patients, 
Na+-K+ ATPase activity has been found to be normal. However a 
decrease in the ethacrynic acid-sensitive efflux, a Na+ exchange mechanism, has 
been reported in cystic fibrosis erythrocytes. These findings suggest that there 
is no fundamental abnormality in the Na+-K+ ATPase enzyme in the 
disease, but there may be a defect in an ethacrynic acid-sensitive 
transport step. Therefore in order to obtain a better understanding of 
the cation transport defect one should measure the binding of labelled 
ethacrynic-acid rather than ouabain. 