Localization of medullary functional abnormalities in experimental papillary necrosis

Renal function was investigated in rats 3 d or 4 wk after an injection of 2-bromoethylamine hydrobromide (BEA) 40-125 mg/kg body weight. Animals developed necrosis of renal papillary structures other than collecting ducts (subtotal renal papillary necrosis) (RPN) or necrosis of all structures in the distal papilla, including collecting ducts (total RPN). Glomerular filtration rate (GFR) was reduced in animals with total RPN (667 +/- SD 168 microliters/min/100 g body weight, n = 5) in comparison with controls (1065 +/- 103, n = 5; P less than 0.001) but was unimpaired in animals with subtotal RPN (1162 +/- 200, n = 4; P greater than 0.3). Maximum urinary osmolality (Umax) was significantly decreased in subtotal RPN (1241 +/- 388 mOsm/kg, n = 4) and in total RPN (626 +/- 293, n = 5) in comparison with controls (2216 +/- 293, n = 5). Free water reabsorption (TcH2O) was impaired in animals with total RPN but was not significantly reduced in the presence of subtotal RPN. Total RPN did not affect free water formation (CH2O). It is concluded that impaired TcH2O occurs in RPN because of the damage to the collecting duct, and not because of necrosis of the thin limbs juxtamedullary nephrons.