Supplementary Material for: Duration of Gestation and Mode of Delivery Affect the Genes of Transepithelial Sodium Transport in Pulmonary Adaptation

Background: Respiratory distress due to inadequate lung liquid clearance is a significant problem in infants delivered late preterm or early term, especially by elective cesarean delivery (CD). Lung liquid clearance depends on epithelial ion transport and in animals is induced by glucocorticoids. Objectives: In newborn late preterm and term infants to study airway epithelial gene expressions of epithelial sodium channel (ENaC), and the serum and glucocorticoid-inducible kinase 1 (SGK1), and their association with cortisol, mode of delivery, and gestational age (GA). Methods: Infants were delivered at 35^0/7-41^6/7 weeks. Cortisol in umbilical cord plasma was analyzed with liquid chromatography-tandem mass spectrometry. ENaC and SGK1 mRNAs in airway epithelial cells obtained within 3 h and at 1 day postnatally were quantified with real-time PCR. Results: ENaC and SGK1 mRNAs were significantly lower in late preterm and early term infants than in those ≥39^0/7 weeks. Significant correlations existed between both ENaC and SGK1 and cord cortisol and GA. In term infants, SGK1 mRNA at 1.5 h was higher after vaginal delivery than elective CD. Conclusions: In late preterm and early term infants, low expression of ENaC and SGK1 may parallel insufficient lung liquid clearance predisposing to respiratory distress. Lower SGK1 expression after term CD could translate into insufficient sodium and lung liquid absorption. The findings demonstrate a central role for cortisol in regulation of ENaC and potentially perinatal sodium and lung liquid clearance.