AJP - Heart and Circulatory Physiology, Vol 250, Issue 1 16-H21, Copyright © 1986 by American Physiological Society
Electrical conductivity and its use in estimating an equivalent pore size for arterial endothelium
M. P. O'Donnell and F. F. Vargas
Transport characteristics of capillary endothelia have been studied in
numerous preparations. Little is known, however, regarding transport across
the ultrastructurally similar arterial endothelium. The present studies
describe a method for determining endothelial electrical resistance in the
isolated, Ringer-perfused rabbit aorta. By use of silver-silver chloride
electrodes, total resistance (RT) of the vessel wall was found to be 18.4
+/- 6.5 omega . cm2 (mean +/- SD; n = 10) in response to transmural passage
of constant current pulses. After detergent removal of the endothelium,
outer layer resistance (Rol) was 8.7 +/- 5.1 omega . cm2. Endothelial
resistance (Re) was calculated to be 9.7 +/- 4.1 omega . cm2, since RT =
Rol + Re. Combination of Re with previously measured hydraulic conductivity
of this endothelium yielded an equivalent endothelial pore radius of 85 A,
whereas a fractional pore area of 6.5 X 10(-4) was estimated from
conductivity data. An alternative analysis demonstrated an endothelial slit
width of 102 A. Re is similar to electrical resistances of leaky epithelia,
frog mesenteric capillary, and frog muscle capillary, suggesting similar
permeability characteristics in both arterial and capillary endothelia.
