Response to acute protein load in kidney donors and in apparently normal postacute glomerulonephritis patients: evidence for glomerular hyperfiltration.

25 kidney donors who had undergone nephrectomy 1-11 years ago, 35 patients followed up for 13 years after poststreptococcal glomerulonephritis, and 44 controls were investigated for their capacity to increase their glomerular filtration rate after an acute oral load of 100-150 g of protein. Their mean baseline creatinine clearances (Ccrl, ml/min +/- SEM) were similar (controls 108.5 +/- 6.1; kidney donors 115.4 +/- 8.54; postacute nephritis 82.0 +/- 6.45), but the postmeal filtration rates (Ccr2) were significantly (p less than 0.05) lower in the two patient groups (kidney donors 137.4 +/- 11.60; postacute nephritis 90.3 +/- 5.30) than in the controls (161.5 +/- 9.39), as was the Ccr2/Ccr1 ratio (p less than 0.01, controls 1.58 +/- SEM 0.10; kidney donors 1.20 +/- 0.07; postacute nephritis 1.18 +/- 0.08). In normal individuals the degree of change was inversely related to the initial creatinine clearance and varied from 135.6% +/- 43.0 when Ccrl was less than 70 ml/min to 32.7% +/- 9.50 when Ccrl was 130 ml/min or higher. This relative response was decreased in kidney donors and postacute nephritis patients. Kidney donors and apparently normal postacute nephritis patients thus have diminished renal reserve capacity.