Characterisation of non-transferrin-bound iron (ferric citrate) uptake by rat hepatocytes in culture
Characterisation of non-transferrin-bound iron (ferric citrate) uptake by rat hepatocytes in culture
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DOI：
10.1016/s0304-4165(97)00120-7
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发表时间：
1998-03-12
影响因子：
3
通讯作者：
Morgan, EH
中科院分区：
文献类型：
--
作者：
Baker, E;Baker, SM;Morgan, EH
在铁过载的情况下，血浆中的转铁蛋白可以完全饱和，血浆可以运输非转铁蛋白结合的铁，并迅速被肝脏清除。大部分铁被柠檬酸盐络合。本研究的目的是利用大鼠肝细胞培养模型来描述柠檬酸铁被肝细胞吸收的机制。细胞在培养一天后，与Fe-59标记的柠檬酸铁一起孵育不同时间，然后洗涤，通过放射性测量测定细胞膜和细胞内区室的铁摄取。铁的最大内化率发生在铁：柠檬酸摩尔比为1:100或更大，pH约为7.4，细胞外Ca2+浓度为1.0mM。铁的吸收表现为Michaelis-Menten动力学，是一个温度依赖的过程。细胞在37℃下铁内化的K-m和V-max分别约为7 μ M和2nmol/mg DNA/min (25 × 10(6)个原子/细胞/min)；Arrhenius活化能为35 kJ/mol。过渡金属Zn2+、Co2+和Ni2+在铁浓度为10倍和100倍时抑制了铁的吸收。在铁浓度分别为1 μ M和2.5 μ M时，柠檬酸铁的铁内化率是铁转铁蛋白的20倍左右。铁负载肝细胞对铁的摄取速率与正常肝细胞无显著差异。这些实验表明，原代培养的大鼠肝细胞以柠檬酸铁的形式吸收非转铁蛋白结合的铁的能力很高，并且通过促进扩散发生摄取。铁运输过程似乎不受细胞铁水平的调节。(C) 1998爱思唯尔科学有限公司
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.