Urodilatin, a kidney-derived natriuretic factor, is excreted with a circadian rhythm and is stimulated by saline infusion in man.

Urodilatin is a recently described, presumably kidney-derived member of the atrial natriuretic peptide family. The first data on a physiological role for urodilatin in the regulation of sodium homeostasis in humans is presented in this work. Urinary urodilatin excretion during a 9-day study in healthy volunteers paralleled the circadian rhythm in urinary sodium excretion. Furthermore, urodilatin and sodium excretion were slightly increased during the first 3 h after an acute isotonic saline infusion and about three-fold elevated during 14 h postinfusion; both parameters remained closely correlated up to 28 h postinfusion. These data suggest that urodilatin is involved in the circadian regulation of sodium excretion and is a physiological regulator of long-term sodium excretion after an acute saline infusion.