Quail E A, Morgan E H
Department of Physiology, University of Western Australia, Nedlands, Australia.
J Cell Physiol. 1994 May;159(2):238-44. doi: 10.1002/jcp.1041590207.
Reticulocytes suspended in low ionic strength media such as isotonic sucrose solution efficiently take up non-transferrin-bound iron and utilize it for heme synthesis. The present study was undertaken to determine how such media facilitate iron utilization by the cells. The effects of changes in membrane surface potential, membrane permeability, cell size, transmembrane potential difference, oxidation state of the iron, and lipid peroxidation were investigated. Iron uptake to heme, cytosol, and stromal fractions of cells was measured using rabbit reticulocytes incubated with 59Fe-labelled Fe(II) in 0.27 M sucrose, pH 6.5. Suspension of the cells in sucrose led to increased membrane permeability, loss of intracellular K+, decreased cell size, and increased transmembrane potential difference. However, none of these changes could account for the high efficiency of iron uptake which was observed. The large negative membrane surface potential which occurs in sucrose was modified by the addition of mono-, di-, tri-, and polyvalent cations to the solution. This inhibited iron uptake to a degree which for many cations varied with their valency. Other cations (Mn2+, Co2+, Ni2+, Zn2+) were also very potent inhibitors, probably due to direct action on the transport process. Ferricyanide inhibited iron uptake, while ferrocyanide and ascorbate increased the uptake of Fe(III) but not Fe(II). It is concluded that the high negative surface potential of reticulocytes suspended in sucrose solution facilitates iron uptake by aiding the approach of iron to the transport site on the cell membrane. The iron is probably transported into the cell in the ferrous form.
悬浮于低离子强度介质（如等渗蔗糖溶液）中的网织红细胞能有效摄取非转铁蛋白结合铁，并将其用于血红素合成。本研究旨在确定此类介质如何促进细胞对铁的利用。研究了膜表面电位、膜通透性、细胞大小、跨膜电位差、铁的氧化态以及脂质过氧化的变化所产生的影响。使用在pH 6.5的0.27 M蔗糖中与59Fe标记的Fe(II)孵育的兔网织红细胞，测定细胞血红素、胞质溶胶和基质部分对铁的摄取。将细胞悬浮于蔗糖中会导致膜通透性增加、细胞内钾离子流失、细胞大小减小以及跨膜电位差增加。然而，这些变化均无法解释所观察到的铁摄取高效率现象。向溶液中添加单价、二价、三价和多价阳离子可改变蔗糖中出现的大的负膜表面电位。这在一定程度上抑制了铁的摄取，许多阳离子的抑制程度随其价态而变化。其他阳离子（Mn2+、Co2+、Ni2+、Zn2+）也是非常有效的抑制剂，可能是由于对转运过程的直接作用。铁氰化物抑制铁摄取，而亚铁氰化物和抗坏血酸增加Fe(III)的摄取，但不增加Fe(II)的摄取。结论是，悬浮于蔗糖溶液中的网织红细胞的高负表面电位通过帮助铁接近细胞膜上的转运位点来促进铁摄取。铁可能以亚铁形式转运进入细胞。
