Intrarenal distribution of blood flow and glomerular filtration during chronic unilateral ureteral obstruction.

Paired hydronephrotic (HN) and hypertrophic (HT) rat kidneys were studied after 6 days with complete unilateral ureteral obstruction without exposing the kidneys. Total HN renal blood flow (RBF), estimated by total microsphere (MS) uptake and from local 125I-antipyrine (Ap) uptake, averaged about 3/4 of control. HN kidney GFR was reduced to about 1/2 of control level as estimated from inulin clearance of HT kidney times the HN to HT ratio for mean single nephron filtration rate, determined by 14C-ferrocyanide. Whereas blood flow (Ap) was proportionately reduced in outer and inner cortex (OC and IC), fractional flow to the outer medulla (OM) was doubled as compared to controls (p less than 0.01). Filtration was well preserved in deep as compared to superficial glomeruli with a smaller deep nonfiltering fraction (p less than 0.02). Thus the results oppose the current concept that HN is characterized by disproportionate circulatory damage to IC and OM with little or no filtration in deep nephrons. In HT kidneys average RBF (MS) and GFR rose by about 1/2. Whereas total blood flow (Ap) rose proportionately in OC and IC, it remained at control level in OM, indicating dissociation between the total RBF and GFR and the effective blood flow to the OM zone.