Modulation of sodium transport in alveolar epithelial cells by estradiol and progesterone

Abstract

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 μM) and P (0-2.8 μM). Short-circuit currents (ISC) were measured, showing an increase by E2 and P in a dose-dependent manner. The Na,K-ATPase subunits -α1 and -β1 were detected by Western blotting, but total expression was not significantly altered. Furthermore, all three epithelial Na channel (ENaC) subunits -α, -β, and -γ were detected, with trends toward a higher expression in the presence of E2 and P. Real-time PCR revealed an increase of α- and β-ENaC expression but no alteration of γ-ENaC. In addition, the mRNA expression of cystic fibrosis transmembrane conductance regulator (CFTR) and Na,K-ATPase-β1 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. © 2011 International Pediatric Research Foundation, Inc.