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.


OBJECTIVE
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.
Department of Pediatrics, Hospital for Children and Adolescents, Helsinki University Central Hospital, Helsinki, Finland. cecilia.janer@hus.fi
Cecilia
C
Janér
Otto
O
Helve
Olli M
OM
Pitkänen
M Anneli
MA
Kari
Outi M
OM
Peltoniemi
Mikko
M
Hallman
Petteri
P
Hovi
Sture
S
Andersson
D001623:Betamethasone / Q000008:administration & dosage*; D001997:Bronchopulmonary Dysplasia / Q000188:drug therapy; D004305:Dose-Response Relationship, Drug; D053503:Epithelial Sodium Channels / Q000235:genetics*; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D005865:Gestational Age; D005938:Glucocorticoids / Q000008:administration & dosage*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008297:Male; D009297:Nasal Mucosa / Q000502:physiology; D011247:Pregnancy; D011650:Pulmonary Alveoli / Q000502:physiology; D012127:Respiratory Distress Syndrome, Newborn / Q000188:drug therapy*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D053503:Epithelial Sodium Channels; D005938:Glucocorticoids; C507045:SCNN1A protein, human; C507048:SCNN1B protein, human; C507052:SCNN1G protein, human; D001623:Betamethasone