Iron uptake by human reticulocytes at physiologic and sub-physiologic
concentrations of iron transferrin: the effect of interaction with aluminum
transferrin [see comments]
M Cochran, V Chawtur, ME Jones and EA Marshall
School of Medicine, Flinders University of South Australia, Bedford Park.
We have studied the interaction, in vitro, between diferric transferrin
(FeTr), aluminum transferrin (AlTr), and human reticulocytes harvested from
human placental blood. In particular, we aimed to determine the extent to
which the kinetics of AlTr and FeTr differed. Using transferrin labeled
with either 59Fe or 125I, the association of radiotracer with
reticulocytes, as a function both of time and of transferrin concentration,
was examined. Under the conditions of the experiments, the data are
consistent with a mechanism involving at least three processes. Two early
processes acting in parallel behave as a high-affinity saturable receptor
and a low-affinity non-saturable receptor, neither of which distinguish
between AlTr and FeTr. In a subsequent process, AlTr and FeTr exhibit
different kinetics. This third process may be saturated by FeTr but not by
AlTr. Interpreted in terms of a current conventional view of
metallo-transferrin uptake, we conjecture that the early parallel processes
involve cell surface phenomena including classical transferrin-receptor
binding, and that the subsequent process represents events, possibly
intracellular, involved in metallo-transferrin dissociation or further iron
transport. The extent to which AlTr influences the interaction of FeTr with
reticulocytes offers insight into both the normal physiology of iron uptake
and the potential for toxicity by aluminum.
Volume 77,
Issue 11,
pp. 2347-2353,
06/01/1991
Copyright © 1991 by The American Society of Hematology
