AJP - Renal Physiology, Vol 257, Issue 6 925-F936, Copyright © 1989 by American Physiological Society
Functional studies in experimental renal cortical necrosis in the rat
M. Martinez-Maldonado, J. M. Lopez-Novoa, E. Fernandez-Repollet, C. Baldizon, S. Opava-Stitzer and J. E. Benabe
Renal Metabolic Laboratory, Veterans Administration Medical Center, San Juan, Puerto Rico.
Necrosis of the outer two-thirds of the cortex (CN) was induced with
boiling water in the left kidney of rats. Two days afterward, morphological
damage was shown to be limited to the superficial cortex; deep nephron
population was well-preserved. Glucose reabsorption under basal and glucose
loading conditions, and extraction of p-aminohippurate, used as indices of
proximal tubule integrity, were normal in control and experimental kidneys
48 h after cortical necrosis. Basal fractional water and electrolyte
excretion did not differ between control and experimental kidneys.
Calculated mean single-nephron glomerular filtration rate (GFR) and plasma
flow for superficial (SupGFR and SupNPF) and juxtamedullary nephrons (JMGFR
and JMPF) were similar to those obtained by micropuncture and Hanssen's
technique for SupGFR, and for JMGFR by Hanssen's. Volume expansion led to a
27% increase in calculated SupGFR, but no change in JMGFR. The JMPF
increased by 81%, whereas SupNPF increased by only 23%, suggesting that, in
this model, GFR of deep nephrons may be independent of plasma flow. The
results indicate that deep nephrons retain their functional integrity 48 h
after cortical necrosis. After volume expansion fractional excretion of
sodium was greater, and fractional water reabsorption less, in CN than in
control kidneys. Thus handling of sodium and water by superficial and deep
nephrons under basal conditions was similar, but reabsorptive capacity for
deep nephrons of CN was lower during volume expansion. The present studies
suggest that deep nephrons can maintain relatively normal function in
cortical necrosis.
