AJP - Heart and Circulatory Physiology, Vol 273, Issue 3 1049-H1057, Copyright © 1997 by American Physiological Society
Assessment of protein permeability in normal human systemic circulation
C. Shanholtz, P. White Jr, S. Permutt, J. T. Sylvester and R. Brower
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA.
Vascular permeability to oncotic agents is an important determinant of
transvascular fluid flux (J) and systemic fluid balance. In this study, a
technique was developed to measure protein reflection coefficients (omega)
for albumin (Alb), immunoglobulin (Ig) G, and IgM in the intact human
systemic circulation to evaluate the role of vascular protein permeability
in health and disease. A mathematical model was developed to calculate
omega in the forearm circulation from changes in venous hematocrit and
protein concentration that occur during edema formation. Assumptions
required for the model were validated in an initial set of experiments in
normal subjects when edema was induced by inflating a pneumatic cuff on the
upper arm. A second series of experiments assessed omega for Alb, IgG, and
IgM in men (n = 7) and in women in the follicular (n = 5) and luteal (n =
4) phases of the menstrual cycle. There was an increasing trend in omega
with molecular size in aggregated subjects [omega Alb = 0.81 +/- 0.12 (SE),
omega IgG = 0.88 +/- 0.12, omega IgM = 0.92 +/- 0.18; P = 0.088]. These
values were consistent with those obtained with in vitro preparations.
omega values were lower in women in the luteal than in the follicular phase
(P = 0.047). We conclude that the assumptions required for this model can
be achieved in the intact forearm circulation and that there are menstrual
phase-related differences in vascular protein permeability in normal women.
