The purpose of this study was to examine the course of residual glomerular function in two models of renal ablation both with equivalent degrees of nephron reduction (1 1/3 nephrectomy). The remnant group underwent right nephrectomy and infarction of one third of the left kidney, yielding constant proportions of remnant deep and superficial nephrons, while the bromoethylamine (BEA) group underwent right nephrectomy and chemical ablation by BEA (50 mg intravenously [IV]) of the deep nephrons of the left kidney, leaving superficial nephrons. Ten weeks following ablation, greater whole kidney permselective defects indicative of worse injury occurred in the remnant group compared with the BEA group, as manifested by increased excretion of total protein (.65 +/- .14 v .23 +/- .04 g/d [65 +/- 14 v 23 +/- 4 mg/24 h]; P less than 0.05) and greater fractional clearance of albumin (71.8 +/- 42.1 v 9.0 +/- 3.4 X 10(-4); P less than 0.05) and IgG (17.9 +/- 10.2 v 3.6 +/- 1.2 x 10(-4); P less than 0.05). Glomerular filtration rate (GFR) and renal plasma flow (RPF) were similar in the ablated groups, but lower than a sham-operated control group. Superficial single nephron GFR (SNGFR) and mean glomerular capillary pressure (PGC) were elevated similarly in the ablated groups compared with the control group. Based on the differences in the two models, the site of the increased proteinuria in the remnant group could be the deep nephrons and/or the nephrons adjacent to the scar.