AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 2 280-R283, Copyright © 1984 by American Physiological Society
Heterogeneity of the plasma iron pool: explanation of the Fletcher-Huehns phenomenon
H. A. Huebers, E. Huebers, E. Csiba and C. A. Finch
Observations on iron uptake by reticulocytes led Fletcher and Huehns to
suggest differences in the behavior of the two iron-binding sites of the
transferrin molecule. To clarify the continued controversy relating to this
hypothesis, the original studies employing control plasma labeled with
radioiron and the same plasma preincubated with reticulocytes were
reexamined. Regardless of whether human or rabbit plasma was employed,
there was a considerably higher uptake from the control plasma. Isoelectric
focusing procedures and electrophoresis in urea gels revealed that the
conspicuous difference in the amount of iron uptake is the result of
differences in the proportion of di- to monoferric transferrin in the two
plasmas and the competitive advantage of the diferric moiety. These studies
provide an explanation for the Fletcher-Huehns phenomenon without invoking
functional differences between the two sites for iron on the transferrin
molecule.
