Medullary blood flow responses to changes in arterial pressure in
canine kidney.
Majid, Dewan S. A., and L. Gabriel Navar.
Department of Physiology, Tulane University School of Medicine,
1430 Tulane Ave., New Orleans, LA 70112, 504-588-5251
APStracts 2:0213F, 1995.
Although it is well recognized that whole kidney and cortical blood
flow exhibit efficient autoregulation in response to alterations in
renal arterial pressure (RAP), the autoregulatory behavior of
medullary blood flow (MBF) has remained uncertain. We have evaluated
MBF responses to stepwise reductions in RAP for both short-term (2
min, n=6) and longer periods (15 min, n=7) using single fiber laser
-Doppler flowmetry with needle probes inserted into the mid-medullary
region in denervated kidneys of 13 anesthetized dogs. The changes in
cortical blood flow (CBF) were assessed with either a surface probe
or a needle probe inserted into the cortex. Control total renal blood
flow (RBF) assessed by electromagnetic flow probe, in these dogs was
5.2+/-0.3 ml_min-1_g-1 and glomerular filtration rate was 0.97+/-0.05
ml_min-1_g-1 (n=7). RBF, MBF and CBF all exhibited efficient
autoregulatory behavior during changes in RAP from 150 down to 75
mmHg. The slopes of RAP vs RBF, CBF as well as MBF were not
significantly different from zero within this range of RAP. Below RAP
of 75 mmHg, all indices of blood flow showed linear decreases with
reductions in pressure. The data indicate that blood flow in the
renal medulla of dogs exhibits efficient autoregulatory behavior,
similar to that in the cortex.
Received 2 October 1995; accepted in final form 29 November 1995.
APS Manuscript Number F332-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 12 December 95