Effect of extreme prematurity on renal dopamine and norepinephrine excretion during the neonatal period

Dopamine (DA), produced in proximal tubular cells, is believed to be an important intrarenal natriuretic hormone, Experimental studies have shown that the natriuretic effect of DA is less pronounced in the fetal kidney. We have evaluated renal DA and norepinephrine (NE) in the neonatal period, using urinary excretion as an indicator of renally produced/released catecholamines, In very low-birth-weight infants (25-30 weeks gestational age) there was an increase in urinary DA (pmol/mu mol urinary creatinine) and NE (pmol/mu mol urinary creatinine) from 1 to 13 days postnatal age, despite a decrease in sodium excretion. Urinary NE correlated with plasma NE, whereas plasma DA was undetectable. In summary, NE excretion parallels plasma levels and could reflect the general sympathoadrenal activity, whereas DA is primarily of renal origin. Renal DA and NE increase in the first 2 weeks of life in immature infants. We conclude that the catecholamine system of the human kidney undergoes maturational changes postnatally.