Effect of sodium chloride supplementation on urinary endothelin-1 excretion in premature infants.

We investigated the role of endothelin-1 in the renal adaptation to alterations in sodium balance in premature infants. The postnatal course of urinary endothelin-1 excretion, an estimate of renal endothelin-1 production, was compared in premature infants receiving low or high sodium intake. Sodium supplementation was given in a dose of 3 to 5 mmol/kg per day and 1.5 to 2.5 mmol/kg per day at the postnatal ages of 8 to 21 and 22 to 35 days, respectively. Sodium balance and urinary endothelin-1 excretion were determined weekly up to the fifth week of life. Urinary endothelin-1 concentration (expressed in picomoles per liter) and urinary endothelin-1 excretion (expressed either in terms of picomoles per square meter per day or picomoles per millimole creatinine) were significantly lower in infants receiving a high sodium intake compared with those receiving low sodium intake (p < 0.001) in weeks 2 through 5. We conclude that in sodium-depleted premature infants with high urinary sodium excretion, an angiotensin II-mediated increase in renal endothelin-1 production occurs, which acts in concert with angiotensin II to restore sodium balance.