Modulation of Sodium Transport in Alveolar Epithelial Cells by Estradiol and Progesterone

The effects of estradiol (E2) and progesterone (P) on alveolar epithelial Na+ transport were studied in isolated alveolar epithelial cells from 18- to 19-d GA rat fetuses, grown to confluence in serum-free media supplemented with E2 (0-1 mu M) and P (0-2.8 mu M). Short-circuit currents (I-SC) were measured, showing an increase by E2 and P in a dose-dependent manner. The Na,K-ATPase subunits -alpha(1) and -beta(1) were detected by Western blotting, but total expression was not significantly altered. Furthermore, all three epithelial Na+ channel (ENaC) subunits -alpha, -beta, and -gamma were detected, with trends toward a higher expression in the presence of E2 and P. Real-time PCR revealed an increase of alpha- and beta-ENaC expression but no alteration of gamma-ENaC. In addition, the mRNA expression of cystic fibrosis transmembrane conductance regulator (CFTR) and Na,K-ATPase-beta(1) subunit were elevated in the presence of E2 and P. Single-channel patch clamp analysis demonstrated putative highly selective and nonselective cation channels in the analyzed cells, with a higher percentage of responsive patches under the influence of E2 and P. We conclude that E2 and P increased Na+ transport in alveolar epithelial cells by enhancing the expression and activity of ENaC and Na,K-ATPase. (Pediatr Res 69: 200-205, 2011)