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1 Department of Pediatrics and 2 Cardiovascular-Pulmonary Research Laboratory, University of Colorado Health Sciences Center, Denver, Colorado 80262
Hypoxia reduces
alveolar liquid clearance and the nasal potential difference, a marker
of airway epithelial sodium transport. The mechanisms underlying this
impaired epithelial sodium transport in vivo remain uncertain. We
hypothesized that epithelial sodium transport impaired by hypoxia would
recover quickly with reoxygenation and that hypoxia decreases the
expression of lung epithelial sodium channels and Na,K-ATPases. We
studied adult rats exposed to normoxia, hypoxia
(FIO2 = 0.1) for 24 h, or
hypoxia followed by recovery in normoxia. Nasal potential differences
decreased by 40% with hypoxia (P < 0.001), returning
to baseline levels with reoxygenation. Lung Na,K-ATPase activity
decreased by 40% with hypoxia (P = 0.003), recovering
to baseline levels with reoxygenation. Lung expression of mRNA encoding
for epithelial sodium channel (ENaC)-
, -
, and -
or for
Na,K-ATPase-
1 did not change significantly with hypoxia or recovery nor did lung expression of ENaC-
, ENaC-
,
Na,K-ATPase-
1, or Na,K-ATPase-
1 protein.
We conclude that subacute exposure to moderate hypoxia reversibly
impairs airway epithelial sodium transport and lung Na,K-ATPase
activity but that those changes are not due to changes in the lung
expression of sodium-transporting proteins.
pulmonary edema; sodium channels
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