Urodilatin excretion and its correlation with sodium excretion in healthy full-term newborn infants.

BACKGROUND: Urodilatin (URO) is a member of the natriuretic family, cleaved by the kidney, which acts as a paracrine hormone in the regulation of natriuresis and diuresis. In newborn infants the excretion of urodilatin and its biological effects have not been explored. METHODS: We measured urinary URO excretion, by direct RIA (radioimmunoassay), as well as its correlation to neonatal body weight loss, and sodium homeostasis in 30 full-term newborn infants on the 4th day of life. RESULTS: The URO excretion, estimated as URO:creatinine ratio, was significantly correlated to sodium excretion. CONCLUSION: These data show that in full-term newborn infants the mechanisms that control synthesis, excretion and signal transduction of URO are developed and that URO contributes to natriuresis regulation.