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.
Janér
Cecilia
C
Department of Pediatrics, Hospital for Children and Adolescents, Helsinki University Central Hospital, Helsinki, Finland. cecilia.janer@hus.fi
Helve
Otto
O
Pitkänen
Olli M
OM
Kari
M Anneli
MA
Peltoniemi
Outi M
OM
Hallman
Mikko
M
Hovi
Petteri
P
Andersson
Sture
S
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