AJP - Gastrointestinal and Liver Physiology, Vol 256, Issue 6 1022-G1027, Copyright © 1989 by American Physiological Society
Uptake and distribution of transferrin and iron in perfused, iron-deficient rat liver
J. M. Holmes and E. H. Morgan
Department of Physiology, University of Western Australia, Nedlands.
Uptake of transferrin and iron by the rat liver was investigated by
perfusion in vitro with 125I-59Fe-labeled rat transferrin and subcellular
fractionation on sucrose density gradients. Most of the 125I-transferrin
was located in a low-density vesicle fraction. The 59Fe was in three peaks,
of lower, the same, and higher densities than the transferrin peak. Iron
deficiency resulted in a large increase in transferrin and iron uptake into
all subcellular fractions. When livers were perfused with increasing
concentrations of transferrin the uptake into the different peaks of
transferrin and iron increased in a curvilinear fashion, which indicated
that uptake occurred by saturable and nonsaturable processes, both of which
increased in iron deficiency. In contrast, the uptake of 131I-labeled rat
serum albumin increased linearly with concentration, and there was no
difference between control and iron-deficient livers. It is concluded that
iron deficiency leads to an increase in the number of high-affinity
transferrin receptors and receptor-mediated endocytosis of transferrin. It
also increases a nonsaturable transferrin uptake process that is probably
due to adsorptive, but selective, endocytosis of transferrin.
