Nitric oxide inhibits Na+ absorption across cultured alveolar type II monolayers.
We examined the mechanisms by which nitric oxide (.NO) decreased vectorial Na+ transport across confluent monolayers of rat alveolar type II (ATII) cells grown on permeable supports. Amiloride (10 microM) applied to the apical side of monolayers inhibited approximately 90% of the equivalent (Ieq) and the short-circuit (Isc) current, with an half-maximal inhibitory concentration (IC50) of 0.85 microM, indicating that Na+ entry into ATII cells occurred through amiloride-sensitive Na+ channels. .NO generated by spermine NONOate and papa NONOate added to both sides of the monolayers decreased Ieq and increased transepithelial resistance in a concentration-dependent fashion (IC50 = 0.4 microM .NO). These changes were prevented or reversed by addition of oxyhemoglobin (50 microM). Incubation of ATII monolayers with 8-bromoguanosine 3',5'-cyclic monophosphate (400 microM) had no effect on transepithelial Na+ transport. When the basolateral membranes of ATII cells were permeabilized with amphotericin B (10 microM) in the presence of a mucosal-to-serosal Na+ gradient (145:25 mM), .NO (generated by 100 microM papa NONOate) inhibited approximately 60% of the amiloride-sensitive Isc. In addition, after permeabilization of the apical membranes, .NO inhibited the Isc [a measure of Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity] by approximately 60%. We concluded that .NO at noncytotoxic concentrations decreased Na+ absorption across cultured ATII monolayers by inhibiting both the amiloride-sensitive Na+ channels and Na(+)-K(+)-ATPase through guanosine 3',5'-cyclic monophosphate-independent mechanisms.
Guo
Y
Y
Department of Anesthesiology, University of Alabama at Birmingham 35294, USA.
DuVall
M D
MD
Crow
J P
JP
Matalon
S
S
D000042:Absorption; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D015222:Sodium Channels; D009569:Nitric Oxide; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D006152:Cyclic GMP