Influence of the Renin-Angiotensin System and Atrial Natriuretic Peptide on Renal Functional Reserve

Abstract

We studied the renin-angiotensin system (RAS) and atrial natriuretic peptide (ANP) after amino acid loading in order to elucidate whether or not glomerular hyperfiltration is mediated by these hormones. Eight healthy controls without kidney disease (group 1), 8 renal graft recipients (group 2) and 8 patients after nephrectomy (group 3) were studied. Furthermore, we investigated the influence of amino acid loading on RAS and ANP and glomerular filtration during acute application of captopril in healthy controls. Clearances in insulin (CIn) and para-aminohippuric acid (CPAH) were determined during an infusion of 0.9% saline and during amino acid loading. CIn increased in healthy controls from 96.5 +/- 3.3 to 111.9 +/- 4.4 ml/min (p < 0.01), CPAH rose from 577 +/- 28.7 to 618.9 +/- 38 ml/min (p = NS). During the combined application of amino acid infusion and 25 mg captopril, CIN increased to 125.0 +/- 16.4 ml/min/1.73 m2 (p < 0.01) and there was no significant increase in CPAH which was 595 +/- 77 ml/min/1.73 m2. There was no significant change in renal vascular resistance, but filtration fraction increased from 17 +/- 1 to 19 +/- 1% under amino acid infusion and increased further under the application of captopril to 21 +/- 2% (p < 0.05). In renal graft recipients, CIn had a tendency to increase during amino acid infusion from 78.4 +/- 5.8 to 84.7 +/- 6.5 ml/min (p = NS). In patients after nephrectomy, CIn did not increase (84.5 +/- 6 ml/min) but CPAH did from 345.7 +/- 26.3 to 409 +/- 24.1 ml/min (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)