Regulation of iron absorption by cultured intestinal epithelia (
caco-2) cell monolayers with varied fe status 1.
Tapia, Victoria, Miguel Arredondo, and Marco Tulio
N[acute]u[tilde]nez.
Departamento de Biolog[acute]ia, Facultad de Ciencias, Universidad
de Chile, Casilla 653, Santiago-1, Chile.
APStracts 3:0063G, 1996.
Body Fe homeostasis is maintained through the regulation of Fe
absorption by the intestinal epithelia. Working under the hypothesis
that the intracellular concentration of Fe is instrumental in the
control of its transepithelial flux, we investigated in vitro which
steps in Fe absorption are regulated by cellular Fe content. For
that, Caco-2 cells containing different concentrations of
intracellular 55Fe were grown in porous filters, and the apical-to
-cell-to-basolateral flux of 59Fe was then determined. We found that:
1) at low (up to 0.1 mM) intracellular Fe content the apical to basal
Fe transport was primarily regulated by a decrease in apical Fe
uptake (first stage of regulation), 2) at higher levels of
intracellular Fe (0.1-1 mM), the transepithelial Fe flux was
regulated by intracellular factors that sequester most of the Fe
taken up at the apical surface (second stage of regulation), and, 3)
a fraction of the apical to basolateral Fe flux was not regulated by
the intracellular concentration of Fe. Ferritin synthesis preceded
the onset of the second stage of regulation, suggesting a causal
relationship between intracellular Fe levels, ferritin levels, and
regulation of Fe absorption.
Received 24 August 1995; accepted in final form 8 March 1996.
APS Manuscript Number G368-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96