Endothelin-1 and L-Arginine in Preterm Infants with Respiratory Distress

In addition to the immaturity of air sacs and surfactant deficiency, preterm infants with respiratory distress syndrome (RDS) have abnormalities in the pulmonary vascular bed. We aimed to study two known modulators of pulmonary vessels: endothelin-1 (ET-1) and L-arginine. We hypothesized that plasma concentrations of ET-1 and L-arginine could correlate with the severity of RDS. We prospectively studied 71 preterm infants (gestational age = 29 to 35 weeks) with and without RDS. We measured plasma ET-1 by enzyme-linked immunosorbent assay and L-arginine by spectrophotometry. Infants who continued to require oxygen support or died by day of life 28 were considered to have bronchopulmonary dysplasia (BPD). ET-1 concentrations were significantly higher in RDS infants (p = 0.039) than controls. Among infants with RDS, it was significantly higher in those who later developed BPD (p = 0.026). L-arginine was significantly lower in RDS infants (p = 0.001), but did not differ between BPD and non-BPD infants (p = 0.19). There was no correlation between L-arginine and ET-1 (r = 0.1, p = 0.41). The acute phase of RDS is associated with increased plasma concentrations of ET-1 and decreased L-arginine. Infants who later developed BPD had higher plasma ET-1 at birth. Concentrations of ET-1 and L-arginine did not correlate.