AJP - Renal Physiology, Vol 250, Issue 5 901-F906, Copyright © 1986 by American Physiological Society
Effect of albumin on glomerular ultrafiltration coefficient in isolated perfused dog glomerulus
T. A. Fried, R. N. McCoy, R. W. Osgood and J. H. Stein
To evaluate the direct effect of albumin concentration on the glomerular
capillary ultrafiltration coefficient (Kf), we compared the effect of
"normal" (3.4 g/100 ml), "low" (0.1 g/100 ml), and "no albumin" (less than
0.005 g/100 ml) concentration on the determinants of single-nephron
glomerular filtration rate (SNGFR) as measured with the isolated perfused
glomerulus technique. When the albumin concentration was decreased from
normal to low concentrations, the afferent flow rate increased from 318 +/-
147 (mean +/- SE) to 450 +/- 174 nl/min, the filtration fraction increased
from 0.19 +/- 0.04 to 0.35 +/- 0.08, and the SNGFR increased from 49 +/- 21
to 126 +/- 34 nl/min. These changes were associated with a small though
significant increase in Kf from 2.79 +/- 1.01 to 3.74 +/- 0.98 nl/(min X
mmHg) (P less than 0.05). When the albumin concentration was decreased from
low to no albumin the filtration fraction and SNGFR increased even further
and were associated with a marked increase in Kf to a value of 27.04 +/-
11.43 nl/min X mmHg). We conclude that there is very little effect of
decreases in albumin concentration on Kf until extremely low levels are
reached, and at that point there is a marked increase in the
ultrafiltration coefficient. Furthermore, when these extremely low
concentrations of albumin are reached an important role for albumin in the
basic function of the ultrafiltration barrier is demonstrable.
