Journal of Applied Physiology, Vol 61, Issue 6 2035-2039, Copyright © 1986 by American Physiological Society
Transendothelial albumin flux: evidence against asymmetric transport
A. Siflinger-Birnboim, P. J. Del Vecchio, J. A. Cooper and A. B. Malik
We examined the recent proposition (Circ. Res. 57: 903-905, 1985) that the
interstitium-to-luminal transport of albumin is an active phenomenon.
Studies were made using cultured bovine and sheep pulmonary-artery
endothelial cells. The transendothelial 125I-albumin flux from the
luminal-to-abluminal side was compared with the flux from the
abluminal-to-luminal side. The endothelial cells were grown to confluence
on gelatinized-polycarbonated filters separating the abluminal from the
luminal compartments. The albumin concentration in each compartment was 1
g/100 ml to equalize the oncotic pressure gradients. The effect of
hydrostatic pressure was eliminated by maintaining equal fluid levels in
both compartments. The transendothelial albumin flux across the monolayer
was measured by adding the 125I-albumin tracer either on the luminal or the
abluminal side. A double-isotope method was also used to study
bidirectional transendothelial flux of albumin at the same time for the
same cultured endothelium. The results indicated that albumin flux from the
luminal-to-abluminal side was equal to the flux from the
abluminal-to-luminal side. Both bovine and sheep pulmonary artery
endothelial cells in culture behave symmetrically for albumin, suggesting
that albumin is not actively transported from the interstitium to the
lumen.
