Renal and Hemodialysis Clearances of Endogenous Natriuretic Peptide

The purpose of the present study was to assess the plasma levels of atrial natriuretic peptide (ANP) in chronically uremic patients not submitted to dialysis and to determine the predialysis plasma concentration of ANP, the effect of ultrafiltration on plasma levels of ANP (hemodialysis, (HD), and the HD clearance of ANP in a population of adult patients treated with maintenance HD. The mean plasma ANP concentration (pg/ml) in HD was 370.2 ± 35.5 pg/ml (mean ± SEM) before HD and decreased to 165.3 ± 15.2 after HD (p < 0.01). Both value were significantly higher than in controls (28 ± 2; n = 39). The changes in plasma ANP levels correlated inversely with those in plasma protein concentration (r = -0.53; p < 0.03; y = 48.6 ± 0.8 x). ANP clearance across the cuprophan membrane averaged 13 ± 6.4 ml/mn. Resting plasma ANP values in the 16 uremic patients ranged between 16 and 227 pg/ml (124 ± 11 pg/ml). These levels were significantly higher than those observed in controls (p < 0.01). In these patients there was a highly significant correlation between serum creatinine and plasma ANP concentrations (p < 0.01; r = 0.75; y = 0.2 x + 3). Furthermore we report the results of the determination of the renal clearance of ANP in normal dogs. In all dogs a fall in plasma ANP concentration was recorded between the aorta (28.6 ± 4.5 pg/ml) and the renal vein (14.2 ± 2.7 pg/ml). The renal extraction ratio averaged 51.3 ± 3.7%. Mean ANP renal clearance was 38.2 ± 5.2 ml/ mn. These data support the hypothesis that in hemodialyzed patients high circulating concentrations of the natriuretic peptide are due to sodium and water loading. Furthermore, in patients with renal failure an altered rate of ANP metabolism may contribute to the raised plasma ANP levels that are observed. In fact in normal dog our data indicate that the kidney contributes to the clearance of endogenous ANP.