Plasma and urine levels of uroguanylin, a new natriuretic peptide, in nephrotic syndrome.

Uroguanylin, a new natriuretic peptide originally isolated from urine, stimulates the membrane guanylate cyclase C receptor. No information, however, is available on the plasma and urine levels of uroguanylin in nephrotic syndrome (NS), the state associated with sodium and water retention. Using a sensitive radioimmunoassay, we measured the plasma and urine concentrations of immunoreactive (ir-)uroguanylin in NS patients and compared them with those of patients with non-nephrotic glomerulonephritis. Plasma ir-uroguanylin, blood pressure and the cardiothoracic ratio were higher, and urine excretion of ir-uroguanylin was lower in the NS patients. Plasma ir-uroguanylin in the NS patients significantly decreased during remission as compared with findings on admission. There was a significant inverse correlation between the concentration of plasma ir-uroguanylin and that of serum total protein or albumin. Moreover, fluid retention in the NS patients was correlated with the changes in plasma ir-uroguanylin between admission and remission, indicative that the plasma concentration increases with the severity of the nephrotic state. Taking into account its potent natriuretic effect, these findings suggest that uroguanylin may function in the pathophysiological mechanism in NS.