Decreased sodium ion absorption across nasal epithelium of very premature infants with respiratory distress syndrome

Objective and study design: Successful adaptation to air breathing at birth depends on rapid absorption of fetal lung liquid that is mediated by activation of amiloride-sensitive sodium ion channels. To test the relationship between respiratory epithelial Na+ transport and development of respiratory distress syndrome (RDS), we measured nasal transepithelial potential difference (PD) in 31 very premature (less than or equal to 30 weeks of gestation) newborn infants. Infants were retrospectively assigned to RDS (22 infants) and non-RDS (9 infants) groups on the basis of clinical and chest x-ray criteria. Results: Maximal nasal epithelial PD increased with birth weight (-1.2 mV/100 gm) and was lower in infants with RDS (-16.5 +/- 0.6 mV) than in those without RDS (-22.0 +/- 1.3 mV). Infants without RDS had PD values similar to normal fullterm infants. Amiloride inhibition of PD, an index of Na+ absorption,, was significantly lower, within the first 24 hours of life, in infants in whom RDS developed (3.8 +/- 0.2 mV; 29.5% +/- 0.8% inhibition) than in those without RDS (6.1 +/- 0.6 mV; 38.6% +/- 0.5% inhibition). Maximal and amiloride-sensitive PD returned to normal during the recovery phase of RDS. Conclusions: We conclude that Na+ absorption across nasal epithelium increases with increasing birth weight and that impairment of Na+ absorption across the respiratory epithelia of very premature infants may contribute to the pathogenesis of RDS.