Characterisation of non-transferrin-bound iron (ferric citrate) uptake by rat hepatocytes in culture

被引:59
作者
Baker, E [1 ]
Baker, SM [1 ]
Morgan, EH [1 ]
机构
[1] Univ Western Australia, Dept Physiol, Nedlands, WA 6907, Australia
来源
BIOCHIMICA ET BIOPHYSICA ACTA-GENERAL SUBJECTS | 1998年 / 1380卷 / 01期
基金
英国医学研究理事会;
关键词
non-transferrin-bound iron; ferric citrate; hepatocyte; iron transport; (rat);
D O I
10.1016/S0304-4165(97)00120-7
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Under conditions of iron overload plasma transferrin can be fully saturated and the plasma can transport non-transferrin-bound Fe which is rapidly cleared by the liver. Much of this Fe is complexed by citrate. The aim of the present work was to characterise the mechanisms by which Fe-citrate is taken up by hepatocytes using a rat hepatocyte cell culture model. The cells, after one day in culture, were incubated with Fe-59-labelled Fe-citrate for varying time periods, then washed and Fe uptake to the membrane and intracellular compartments of the cell was determined by radioactivity measurements. Maximal rates of internalisation of Fe occurred at a Fe:citrate molar ratio of 1:100 or greater, a pH of approximately 7.4 and an extracellular Ca2+ concentration of 1.0mM. Fe uptake showed Michaelis-Menten kinetics and was a temperature-dependent process. The K-m, and V-max,,, for Fe internalisation by the cells at 37 degrees C were approximately 7 mu M and 2nmol/mg DNA/min (25 X 10(6) atoms/cell/min), respectively; and the Arrhenius activation energy was 35 kJ/mol. The transition metals, Zn2+, Co2+ and Ni2+, inhibited Fe uptake when used at 10 and 100 times the concentration of Fe. The rate of Fe internalisation from Fe-citrate was found to be approximately 20 times as great as that from Fe-transferrin with Fe concentrations of 1 and 2.5 mu M for both forms of Fe. The rate of Fe uptake by iron-loaded hepatocytes obtained from rats which had been fed carbonyl Fe was not significantly different from that by normal hepatocytes. These experiments show that rat hepatocytes in primary culture have a high capacity to take up non-transferrin-bound Fe in the form of Fe-citrate and that uptake occurs by facilitated diffusion. The iron transport process dos not appear to be regulated by cellular Fe levels. (C) 1998 Elsevier Science B.V.
引用
收藏
页码:21 / 30
页数:10
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