Relationship between plasma renin concentration and atrial natriuretic peptide in the human newborn.

To test the hypothesis that atrial natriuretic peptide (ANP) concentration in the newborn is negatively related to plasma renin concentration (PRC), as it is in the adult, we measured the concentration of both substances in the same plasma sample. We studied 24 well term newborns and 20 samples of umbilical venous blood from normal deliveries. Both ANP and PRC are elevated in newborn plasma, but not in umbilical venous plasma. ANP levels on the second day of life are greater than either day 1 or day 3. Linear regression of ANP and PRC demonstrates a highly significant negative correlation [r = -0.65, p less than 0.001], which suggests that the suppression of the renin-angiotensin system by ANP seen in the adult may be intact in the newborn. ANP may act to blunt the effects of the augmented renin-angiotensin system of the newborn and promote normal neonatal diuresis.