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

Uroguanylin, a new natriuretic peptide originally isolated from urine, stim ulates the membrane guanylate cyclase C receptor. No information, however, is available on the plasma and urine levels of uroguanylin in nephrotic syn drome (NS), the state associated with sodium and water retention. Using a s ensitive radioimmunoassay, we measured the plasma and urine concentrations of immunoreactive (ir-)uroguanylin in NS patients and compared them with th ose of patients with non-nephrotic glomerulonephritis. Plasma ir-uroguanyli n, blood pressure and the cardiothoracic ratio were higher, and urine excre tion of ir-uroguanylin was lower in the NS patients. Plasma ir-uroguanylin in the NS patients significantly decreased during remission as compared wit h findings on admission. There was a significant inverse correlation betwee n the concentration of plasma ir-uroguanylin and that of serum total protei n or albumin. Moreover, fluid retention in the NS patients was correlated w ith the changes in plasma ir-uroguanylin between admission and remission, i ndicative that the plasma concentration increases with the severity of the nephrotic state. Taking into account its potent natriuretic effect, these f indings suggest that uroguanylin may function in the pathophysiological mec hanism in NS.