Expression of airway epithelial sodium channel in the preterm infant is related to respiratory distress syndrome but unaffected by repeat antenatal beta-methasone.

BACKGROUND

The airway epithelial sodium channel (ENaC) is rate limiting for postnatal alveolar fluid clearance. Increased lung water content is a feature of respiratory distress syndrome (RDS), which is reduced by antenatal corticosteroid treatment in preterm infants.

OBJECTIVES

Since corticosteroids also induce ENaC gene expression, we studied whether a repeat dose of antenatal beta-methasone affects postnatal expression of airway ENaC.

METHODS

17 pregnant women with imminent preterm birth were randomized to receive a single repeat dose of beta-methasone (12 mg) or placebo (repeat beta-methasone: 8 infants, gestational age (GA) 30.8 +/- 2.2 weeks; placebo: 14 infants, GA 30.4 +/- 2.7 weeks). Expression of alpha-, beta- and gammaENaC subunits in nasal epithelium 1-5 and 20-29 h postnatally was analyzed with reverse transcription-PCR.

RESULTS

There were no differences between the study groups in RDS incidence or ENaC subunit expression (all p > 0.38). Regression coefficients for association of alphaENaC expression at 1-5 h with GA in infants with and without RDS differed significantly (p = 0.023). At 20-29 h, alphaENaC expression was lower in infants with RDS (p = 0.048).

CONCLUSIONS

A single repeat dose of antenatal beta-methasone did not increase ENaC expression, which may in part explain the absence of reduction in RDS incidence.