URODILATIN IS INVOLVED IN SODIUM HOMEOSTASIS AND EXERTS SODIUM-STATE-DEPENDENT NATRIURETIC AND DIURETIC EFFECTS

Urodilatin is involved in sodium homeostasis and exerts sodium-state-d ependent natriuretic and diuretic effects. Eight male volunteers parti cipated in a study consisting of three consecutive phases of 7 days ea ch. The volunteers received a sodium diet with 52, 172.6, and 347.8 mm ol sodium/day. Sodium excretion increased from 57.4 +/- 3.7 via 130.8 +/- 4.6 (P < 0.001) to 322.5 +/- 10.2 mmol/24 h (P < 0.001) at the end of each sodium diet. Urinary urodilatin excretion increased from 24.8 +/- 3.0 via 35.5 +/- 9.0 (P = 0.07) to 49.0 +/- 3.6 fmol/min (P < 0.0 1). At the end of each diet, urodilatin was infused for 2 h at 20 ng . kg body wt(-1). min(-1). Natriuresis increased after low- (4.1 to 52. 9 mmol/h, P < 0.001), normal (6.9 to 44.9 mmol/h, P < 0.05), and high- sodium diet (20.1 to 102.9 mmol/h, P < 0.001). Diuresis increased from 174 to 709 (P < 0.001), 395 to 1,026 (P < 0.05), and 266 to 1,339 ml/ h (P < 0.001). The present results indicate that endogenous urodilatin plays an important role in sodium homeostasis and that renal response to exogenous urodilatin is modulated by sodium balance.