Circulating levels of endothelin and atrial natriuretic factor during postnatal life

We determined plasma endothelin‐1‐like immunoreactivity and atrial natriuretic factor concentrations in preterm and full‐term newborn infants during the first month of life. Plasma endothelin‐1‐like immunoreactivity levels were far greater than those of maternal blood in the newborn infants. The highest plasma endothelin‐1‐like immunoreactivity levels were observed on the first day of life (8.7 ± 3.7 pmol/l) and gradually decreased with age. There was no significant difference in plasma endothelin‐1‐like immunoreactivity levels between preterm and full‐term infants. A good correlation was observed between plasma endothelin‐1‐like immunoreactivity levels and atrial natriuretic factor concentrations (p < 0.01). These results suggest that circulating endothelin may regulate the cardiovascular system in the newborn period.