AJP - Heart and Circulatory Physiology, Vol 253, Issue 1 194-H204, Copyright © 1987 by American Physiological Society
Integral-mass balance method for determination of solvent drag reflection coefficient
M. B. Wolf, P. D. Watson and D. R. Scott 2nd
We have developed the integral-mass balance (IMB) method to measure the
solvent drag reflection coefficient (sigma f) for transcapillary
macromolecular transport in skeletal muscle and other organs. Of course,
sigma f is calculated from the cumulative amounts of water and
macromolecule that move convectively across the microvascular membrane as
determined from changes in hematocrit and plasma macromolecule
concentration over a period of fluid filtration. We have investigated the
effects of both theoretical and experimental factors that affect the
validity and accuracy of the method. The effect of the following factors on
sigma f determination by the IMB method were explored: low Peclet number;
random-measurement errors; and systematic errors due to vascular leakage,
hemolysis of red blood cells, evaporation, and osmolality changes. We found
that all of these factors produced overestimations of sigma f, but their
effects could be corrected. Also, appropriate experimental design could
minimize these effects. Experiments using the IMB method in the isolated,
perfused cat hindlimb preparation to determine sigma f for albumin and
plasma proteins resulted in mean values of 0.82 +/- 0.08 (SD) (n = 7) and
0.83 +/- 0.02 (n = 4), respectively.
