AJP - Endocrinology and Metabolism, Vol 252, Issue 3 E327-E333, Copyright © 1987 by American Physiological Society
Portal copper transport in rats by albumin
D. T. Gordon, A. S. Leinart and R. J. Cousins
The distribution of newly absorbed copper among serum proteins obtained
from the portal circulation of rats was examined by conventional and
high-performance gel filtration chromatography, affinity chromatography,
and Western blotting. Within 10-30 min after being administered by gavage
or directly into the intestine, 67Cu and 64Cu, respectively, were recovered
in the albumin fraction. By 8 h after administration of the radionuclides,
virtually all of the radioactivity was found with ceruloplasmin. Affigel
blue fractionation and subsequent Superose-6 chromatography further
demonstrated that all of the copper in the albumin-containing fractions was
in fact bound to this protein rather than high molecular weight moieties.
Vascular perfusion of the isolated rat intestine, where 64Cu was infused
into the lumen, showed that newly absorbed 64Cu in the vascular perfusate
collected from the cannulated portal vein was associated with albumin.
Uptake of radioactivity by isolated rat liver parenchymal cells from medium
containing rat serum with 67Cu bound to albumin was demonstrated. In vitro
binding of 64Cu to serum proteins that were transferred to nitrocellulose
by Western blotting techniques showed that albumin is essentially the only
protein that binds appreciable amounts of copper. The data suggest that
albumin is the plasma protein that is responsible for the initial transport
of copper after absorption.
