Rationale: Fetal lung liquid secretion is coupled with chloride transport into the lung lumen. The postnatal clearance of lung liquid is dependent on osmotic force generated by active sodium absorption.
Objective: To study the interaction between airway epithelial sodium transport and postnatal lung function.
Methods: We determined lung compliance and nasal transepithelial potential difference as a measure of airway ion transport and epithelial sodium channel gene expression in 41 healthy newborn infants during the first 50 h after birth.
Measurements and main results: Lung compliance improved significantly during the study period, whereas nasal potential difference remained constant. There was a significant decrease in the expressions of beta and gamma subunits of the epithelial sodium channel. A positive correlation existed between amiloride-sensitive nasal potential difference measured at 1-4 h of age and lung compliance at 21-27 h of age. We found no correlation between the molecular data and functional measurements.
Conclusions: An important part of pulmonary adaptation takes place during the first hour after birth. The improvement of lung compliance continues over the first postnatal days and coincides with down-regulation of epithelial sodium channel beta and gamma subunit expression.