CHAPEL HILL - By studying patients with a rare genetic disorder, scientists at the University of North Carolina at Chapel Hill and colleagues have proven that movement of salt and liquid in and out of lung surface cells plays a central role in regulating the lungs' internal liquid coating.
The finding is important because it confirms a theory of how lungs protect themselves and may suggest better ways of treating cystic fibrosis, the most common lethal genetic illness among whites, the researchers say.
"We found that this rare disorder, which is called systemic pseudohypoaldosteronism, is in a sense the exact opposite of cystic fibrosis," said Dr. Michael R. Knowles, professor of medicine at the UNC-CH School of Medicine and director of the Cystic Fibrosis Therapeutics Development Center. "People with this illness are born without functioning sodium channels that remove salt and liquid coating the airways, and so there is too much liquid. On the other hand, airway cells in people with cystic fibrosis remove too much liquid so that the coating becomes too thick."
In cystic fibrosis, overly sticky lung secretions retard the countless microscopic hair-like structures called cilia that continuously sweep dust and bacteria out of the lungs in a natural cleansing mechanism, Knowles said. Infections and the resulting lung damage eventually kill young patients.
A report on the findings appears in Thursday's issue (July 15) of the New England Journal of Medicine.
Researchers studied in detail nine pseudohypoaldosteronism patients ranging in age from 1.5 years to 22 years in North Carolina, California and Israel.
They tested for mutations in lung surface cell sodium channel genes,
estimated sodium transport rates in the airways and determined the volume and
ion composition of airway surface liquids. They also reviewed clinical
information about patients, collected laboratory data relevant to lung
Contact: David Williamson
University of North Carolina at Chapel Hill