1. The effects of synthetic α-human atrial natriuretic peptide (α-hANP) on urinary protein excretion were examined in nine healthy subjects and 20 patients with primary glomerular diseases who had proteinuria of 1.0 g or more per day. Synthetic α-hANP was intravenously infused into supine subjects at a rate of 8.3 pmol min−1 kg−1 for 40 min

2. Before α-hANP infusion, the plasma concentration of immunoreactive α-hANP was significantly higher in the patients with glomerulonephritis than in the normal subjects (44.3 ± 8.7 vs 19.4 ± 3.0 pmol/l, mean ± sem, P < 0.01) and it showed a positive correlation with mean arterial pressure (rs = 0.84, P < 0.001) and a negative correlation with creatinine clearance (rs = −0.50, P < 0.01)

3. During infusion of α-hANP, although the urinary excretion of protein did not change significantly in the normal subjects, it increased from 0.6 ± 0.2 to 3.0 ± 0.8 mg min−1 m−2 (P < 0.001) in the patients with glomerulonephritis. The urinary protein/creatinine ratio did not change significantly in the former (from 0.18 ± 0.05 to 0.22 ± 0.06; NS), whereas it rose from 3.25 ± 0.94 to 7.62 ± 1.31 (P < 0.001) in the latter

4. The urinary excretions of albumin and of α1-, α2-, β- and γ-globulins, which were electrophoretically analysed, all increased in eight nephrotic patients during or immediately after infusion of α-hANP

5. The α-hANP infusion increased urinary volume, urinary excretion of sodium and creatinine clearance in the glomerulonephritic patients, whereas the changes in urinary volume and creatinine clearance were not significant in the normal subjects. Renal blood flow did not show any significant changes in either group. Packed cell volume increased slightly, but significantly, in the two groups, whereas plasma renin activity did not show any significant changes in either group

6. These results suggest that α-hANP increases the transglomerular permeability to plasma protein in damaged glomeruli, most likely affecting the steric hindrance.

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