AJP - Heart and Circulatory Physiology, Vol 235, Issue 5 592-H600, Copyright © 1978 by American Physiological Society
Evaluation of methods of measuring glomerular and nutrient blood flow in rat kidneys
W. E. Yarger, M. A. Boyd and N. W. Schrader
In normal rats, glomerular plasma flow rates (GPF) were estimated from the
uptake of microspheres, and single-nephron filtration rates were estimated
by Hanssen's technique in order to calculate single-nephron filtration
fractions (SNFF) for outer (C1), middle, (C2), and deep (C3) nephrons. With
large microspheres (15 micron), SNFF averaged 0.19, 0.41, and 0.63, and
with small microspheres (9 micron), SNFF averaged 0.25, 0.48, and 0.42 for
areas C1, C2, and C3, respectively. Kidney filtration fractions (FF)
averaged 0.36. Because microsphere experiments in normal rats have
generally suggested that SNFF-C1 and FF are similar, we conclude that both
types of microspheres overestimated outer cortical plasma flow rates, and
probably underestimated inner cortical plasma flow rates. In addition, not
all of the smaller microspheres were trapped in the glomeruli. Nutrient
blood flow rates were estimated from the uptake of 86Rb. Values ranged from
7.3 ml/g per min in the outer cortex to 4.7 ml/g per min in the inner
cortex. Because these values are very similar to measurements made by
several other techniques, we conclude that 86Rb uptake adequately estimates
cortical blood flow. Medullary blood flow estimates, however, increased
with time and were probably too high.
