We investigated whether adenovirus-mediated transfer of genes encoding for subunits of the Na,K-ATPase increases transepithelial Na+ transport in rat fetal distal lung epithelial (FDLE) monolayers and renders them more resistant to hydrogen peroxide injury. FDLE cells, isolated from rat fetuses at a gestational age of 19 to 20 d (22 d = term), were seeded on filters and infected with replication-incompetent human type 5 adenoviruses containing complementary DNAs encoding for rat Na,K-ATPase α1 or β1 subunits (adα1 and adβ1, respectively). Once confluent monolayers were formed, the filters were mounted in Ussing chambers and short circuit currents (lsc) were measured. Increased levels of α1 or β1 subunit proteins after infection with adα1 and adβ1, respectively, were confirmed by Western blot analysis. Baseline lsc increased after transfection with 2 plaque-forming units (pfu) of adβ1 from 5.1 ± 0.3 to 6.1 ± 0.3 μA/cm2 (mean ± SEM; P < 0.05). Permeabilization of the apical membrane with amphotericin B caused a large increase in lsc; the ouabain-sensitive component of the amphotericin B-elicited lsc (ouabmax) was increased from 4.0 ± 0.2 (n = 69) in controls to 4.8 ± 0.2 (n = 15), 5.9 ± 0.3 (n = 53), 6.9 ± 0.4 (n = 25), 7.7 ± 0.9 (n = 16) in monolayers infected with 1, 2, 11, and 22 pfu of adβ1, respectively; transfection with adα1 had no effect on any measured variables. Further, transfection with adβ1 in comparison to noninfected monolayers resulted in higher baseline and ouabmax lsc after injury with 500 μM H2O2. We conclude that overexpression of the β1 subunit of the Na,K-ATPase may help maintain normal levels of vectorial Na+ transport across ATII cell monolayers in pathologic conditions.