R. Wodopia et al., Hypoxia decreases proteins involved in epithelial electrolyte transport inA549 cells and rat lung, AM J P-LUNG, 279(6), 2000, pp. L1110-L1119
Citations number
37
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY
Fluid reabsorption from alveolar space is driven by active Na reabsorption
via epithelial Na channels (ENaCs) and Na-K-ATPase. Both are inhibited by h
ypoxia. Here we tested whether hypoxia decreases Na transport by decreasing
the number of copies of transporters in alveolar epithelial cells and in l
ungs of hypoxic rats. Membrane fractions were prepared from A549 cells expo
sed to hypoxia (3% O-2) as well as from whole lung tissue and alveolar type
II cells from rats exposed to hypoxia. Transport proteins were measured by
Western blot analysis. In A549 cells, alpha (1)- and beta (1)-Na-K-ATPase,
Na/K/2Cl cotransport, and ENaC proteins decreased during hypoxia. In whole
lung tissue, alpha (1)-Na-K-ATPase and Na/K/2Cl cotransport decreased. alp
ha- and beta -ENaC mRNAs also decreased in hypoxic lungs. Similar results w
ere seen in alveolar type II cells from hypoxic rats. These results indicat
e a slow decrease in the amount of Na-transporting proteins in alveolar epi
thelial cells during exposure to hypoxia that also occurs in vivo in lungs
from hypoxic animals. The reduced number of transporters might account for
the decreased transport activity and impaired edema clearance in hypoxic lu
ngs.