IS URODILATIN THE MISSING LINK IN EXERCISE-DEPENDENT RENAL SODIUM RETENTION

The purpose of the present study was to investigate the behavior of pl asma atrial natriuretic peptide [ANP-(99-126)] concentration ([ANP]) a nd renal urodilatin [Uro; ANP-(95-126)] excretion during and after exe rcise and their possible effects on renal Na+ retention. Ten male subj ects performed a cycle ergometer test for 60 min at 60% of maximum wor kload. Blood and urine samples were collected before, during, and up t o 24 h after exercise. During exercise, plasma [ANP] and renal Uro exc retion were oppositely affected: whereas [ANP] increased from 46.5 +/- 5.1 to 124.1 +/- 10.6 pg/ml, urinary Uro excretion decreased from 120 .8 +/- 16.0 to 49.5 +/- 9.8 fmol/min and remained at a lower level unt il 1 h after exercise. Glomerular filtration rate showed lowest values during exercise (from 164.9 +/- 15.3 to 75.8 +/- 10.1 ml/min), and ur ine flow and the fractional excretion rate of Na+ (FENa+) and Cl- (FEC l-) had their nadir during the first hour after exercise. Positive rel ationships were observed between Uro excretion and FENa+ (P < 0.05) an d FECl-, whereas a tendency toward a negative correlation was obtained between [ANP] and FENa+. It seems possible that Uro may be, among oth er factors, involved in the exercise-related regulation of renal Na+ r etention. The specific roles Uro and ANP play during exercise, however , remain to be investigated.