Physiologic significance of nitric oxide and endothelin-1 in circulatory adaptation.

Abstract

The purpose of the present paper was to evaluate the physiologic significance of nitric oxide (NO) and endothelin (ET)-1 in circulatory adaptation in the neonate. The serum levels of NO metabolites (NOx; the sum of nitrites and nitrates) and the plasma level of ET-1 were determined in 14 healthy full-term infants at 0-6 h, 24 h and 5 days after birth. We measured the heart rate, the mean systemic blood pressure and the mean pulmonary arterial pressure, estimated by pulsed Doppler echocardiography, at each time point. The serum concentration of NOx was lowest at birth and increased with age. The plasma concentration of ET-1 was highest at birth and decreased with age. The ratio of NOx to ET-1 was inversely related to the estimated mean pulmonary arterial pressure in the early neonatal period. The ratio of NOx to ET-1 was not correlated with the systemic blood pressure. Increased NO synthesis and decreased production of ET-1 during the early neonatal period may contribute to the decrease in pulmonary arterial pressure.