Changes of Atrial Natriuretic Peptide Level in Patients with Nephrotic Syndrome after Supine Bicycle Exercise

OBJECTIVES The exact role of atrial natriutetic peptide (ANP) in the pathogenesis of edema in nephrotic syndrome (NS) has not been fully elucidated. We aimed to investigate the possible contribution of ANP to edema formation in NS. METHODS We subjected 18 nephrotic subjects and 20 healthy volunteers to supine bicycle exercise (SBE), a maneuver that seemed to increase venous return and to enhance the release of ANP. Plasma concentrations of immunoreactive-ANP were measured before and after SBE by radioimmunoassay. RESULTS There was a significant rise in the plasma concentration of ANP in the controls after SBE (from 31.1 +/- 6.16 to 42.0 +/- 6.01 pg/ml: p < 0.05). Meanwhile, there was no change in plasma concentration of ANP in the patients with NS (from 35.4 +/- 6.04 to 35.1 +/- 5.31 pg/ml). The change in plasma concentration of ANP in controls was significantly different from that in those with NS (p < 0.05). The mean baseline value of ANP in controls was the same as in NS. CONCLUSIONS These results show that SBE was a simple maneuver to stimulate the release of ANP in healthy controls. In contrast, it failed to stimulate the release of ANP in subjects with NS.