Transport of iron and other transition metals into cells as revealed by a
fluorescent probe.
Breuer, William, Silvina Epsztejn, Pnina Millgram, and Ioav Z. Cabantchik.
Dept. of Biological Chemistry, Institute of Life Sciences, Hebrew
University of Jerusalem, Jerusalem, 91904, ISRAEL
APStracts 2:0053C, 1995.
Transport of non-transferrin-bound iron into cells is thought to be mediated
by a facilitated mechanism involving either the trivalent form, Fe(III), or
the divalent form, Fe(II), following reduction of Fe(III) at the cell
surface. We have made use of the probe calcein, whose fluorescence is rapidly
and stoichiometrically quenched by divalent metals such as Fe(II), Cu(II),
Co(II) and Ni(II) and is minimally affected by variations in ionic strength,
Ca(II) and Mg(II). Addition of Fe(II) salts to calcein-loaded human
erythroleukemia K562 cells elicited a slow quenching response which was
markedly accelerated by the ionophore A23187 and was reversed by membrane
permeant but not by impermeant chelators. These observations were confirmed
by fluorescence imaging of cells. Other divalent metals such as Co(II),
Ni(II) and Mn(II)) permeated into cells at roughly similar rates and their
uptake, like that of Fe(II), was blocked by trifluoperazine, bepridil and
impermeant sulfhydryl-reactive organomercurials, indicating the operation of
a common transport mechanism. This method could provide a versatile tool for
studying the transport of iron and other transition metals into cells.
Received 11 August 1994; accepted in final form 9 December 1994
APS Manuscript Number C0471-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1994 The American Physiological Society.
Published in APStracts on 27 February 1995.