Upregulation of sodium conductive pathways in alveolar type II cells in sublethal hyperoxia.
We investigated whether exposure of rats to sublethal hyperoxia (85% O2 for 7 days) raises the levels of proteins antigenically related to Na+ channels in alveolar type II (ATII) cells and, if so, whether this rise was accompanied by an increase in conductive Na+ transport in vitro. ATII cells were isolated from the lungs of these rats at the end of the exposure period. In Western blot studies, a polyclonal antibody raised against Na+ channel protein (NaAb), recognized in a specific manner a 135 +/- 10 kDa polypeptide in plasma membrane vesicles of ATII cells from both control and oxygen-exposed rats. However, higher levels of immunoreactivity were seen in ATII cells from oxygen-exposed rats. When ATII cells were patched in the whole cell mode using symmetrical solutions (150 mM Na(+)-glutamate), outward rectified Na+ currents were observed. When corrected for cell capacitance, both inward and outward currents of ATII cells from rats exposed to hyperoxia were significantly higher than control. Addition of either 1 microM amiloride or 1 microM 5-(N-ethyl-N-isopropyl)-2'-4'-amiloride in the bath solution decreased the magnitude of outward currents of both control and hyperoxic ATII cells by approximately 50%. Taken together, these results indicate that exposure of rats to sublethal hyperoxia results in upregulation of ATII cell conductive pathways with low affinity to amiloride and increased Na+ transport. This may be an early adaptive response that limits the degree of alveolar edema in injured lungs.
Haskell
J F
JF
Department of Anesthesiology, University of Alabama at Birmingham 35233-6810.
Yue
G
G
Benos
D J
DJ
Matalon
S
S
D000222:Adaptation, Physiological; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D000242:Cyclic AMP / Q000378:metabolism; D004553:Electric Conductivity; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism / Q000502:physiology*
D012964:Sodium; D000242:Cyclic AMP; D010100:Oxygen