AJP - Heart and Circulatory Physiology, Vol 255, Issue 3 638-H645, Copyright © 1988 by American Physiological Society
Effect of albumin on the width of water channels in venous endothelium
P. Sanabria and F. F. Vargas
Department of Physiology and Biophysics, Medical School, University of Puerto Rico, San Juan 00936.
The effect of bovine and dog albumin and plasma was measured on the
hydraulic conductivity (Lp) and electrical resistance (R) across the
endothelium of the dog vena cava. An estimate of changes in size of
transendothelial water channels was then obtained by combining Lp and R
values. Dogs were anesthetized with pentobarbital sodium to surgically
remove their thoracic inferior vena cava. Lp was measured by a gravimetric
method at constant vessel volume. R was obtained from the transvascular
voltage changes caused by current pulses. Lp measured at the beginning of
the experiments was 0.97 +/- 0.17 X 10(-7) cm.s-1.cmH2O-1 in plasma and
2.75 +/- 0.48 X 10(-7) cm.s-1.cmH2O-1 in Ringer solution. Bovine albumin
produced an 18% reduction in Lp relative to its value in Ringer solution.
Dog albumin and plasma lowered Lp 50 and 54%, respectively. The differences
were statistically significant with P less than 0.05. R increased from
15.17 +/- 7.0 to 26.5 +/- 16.0 omega.cm2 in dog albumin and 27.4 +/- 9.6
omega.cm2 in dog plasma. Calculations using a model for the
transendothelial channel and equations for Lp and R showed a decrease in
channel width of 172 A due to the protein. This could be accounted for by
the thickness of a monolayer of albumin absorbed to the channel walls.
Results suggest that the permeability response to plasma proteins is a
general property of vascular endothelium.
