Dexamethasone upregulates the Na-K-ATPase in rat alveolar epithelial cells.
Previous studies in kidney, heart, and liver cells have demonstrated that dexamethasone regulates the expression of Na-K-ATPase. In the lungs, Na-K-ATPase has been reported in alveolar epithelial type II (ATII) cells and is thought to participate in active Na+ transport and lung edema clearance. The aim of this study was to determine whether Na-K-ATPase would be regulated by dexamethasone in cultured rat ATII cells. Regulation of the Na-K-ATPase by dexamethasone could lead to a greater understanding of its role in active Na+ transport and lung edema clearance. Rat ATII cells were isolated, plated for 24 h, and exposed to 10(-7) and 10(-8) M dexamethasone. These cells were harvested at 0, 3, 6, 12, and 24 h after dexamethasone exposure for determination of steady-state Na-K-ATPase mRNA transcript levels, protein expression, and function. The steady-state Na-K-ATPase beta1-mRNA transcript levels increased in ATII cells 6, 12, and 24 h after dexamethasone exposure (P < 0.05). However, the steady-state alpha1-mRNA transcript levels were unchanged. The protein expression for the alpha1- and beta1-subunits increased in ATII cells exposed to dexamethasone compared with controls in association with a temporal increase in Na-K-ATPase function after dexamethasone exposure. These results suggest that dexamethasone regulates Na-K-ATPase in ATII cells possibly by transcriptional, translational, and posttranslational mechanisms.
Barquin
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Pulmonary and Critical Care Medicine, Michael Reese Hospital and Medical Center, Chicago, Illinois 60616, USA.
Ciccolella
D E
DE
Ridge
K M
KM
Sznajder
J I
JI
D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004847:Epithelial Cells / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D011650:Pulmonary Alveoli / Q000201:enzymology*; D011654:Pulmonary Edema / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012413:Rubidium / Q000493:pharmacokinetics; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis*; D013997:Time Factors
D003907:Dexamethasone; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium