Characterisation of citrate and iron citrate uptake by cultured rat hepatocytes
Characterisation of citrate and iron citrate uptake by cultured rat hepatocytes
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DOI：
10.1016/s0168-8278(98)80156-6
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发表时间：
1998-10-01
影响因子：
25.7
通讯作者：
Baker, E
中科院分区：
文献类型：
--
作者：
Graham, RM;Morgan, EH;Baker, E
背景/目的：内源性低分子铁络合剂柠檬酸盐被认为是铁转运的重要贡献者，肝脏是铁超负荷疾病患者摄取柠檬酸铁的主要部位。此外，柠檬酸代谢酶，乌头酸酶，与细胞铁代谢的调节有关。本研究旨在探讨柠檬酸和柠檬酸铁在大鼠肝细胞铁摄取中的作用。方法：将培养的大鼠肝细胞在37℃、15min的条件下，加入100 mU的M[C-14]-柠檬酸，加入或不加入1.0 mU的Fe-55。结果：我们的结果表明，柠檬酸铁的摄取是由特定的柠檬酸结合位点介导的，该结合位点在有铁的情况下对柠檬酸的亲和力比在没有铁的情况下表现出更高的亲和力。柠檬酸被肝细胞内化，至少70%在15分钟内被氧化成二氧化碳。柠檬酸的摄取是pH依赖性的，不需要钠的存在，并且随着铁浓度、代谢能、阴离子通道的增加而增加，Na+，K+-ATPase和囊泡酸化对柠檬酸铁的摄取似乎不起作用，但可能涉及功能性的巯基。结论：相对于孵育介质，铁与柠檬酸摩尔比较高的柠檬酸铁络合物优先与膜结合，或一旦柠檬酸盐将其铁输送到膜上，复合体解离和组分单独内化。
Background/Aims: The endogenous low-molecular weight iron chelator, citrate, is considered to be an important contributor to iron transport and the liver the main site of uptake of iron citrate in subjects suffering from diseases of iron overload. Moreover, the citrate-metabolising enzyme, aconitase, is implicated in the regulation of cellular iron metabolism. This study was undertaken to determine the role of citrate and ferric citrate in the uptake of iron by rat hepatocytes.Methods: Cultured rat hepatocytes were incubated (37 degrees C, 15 min) with 100 mu M [C-14]-citrate in the presence or absence of 1.0 mu M Fe-55. Membrane-bound and intracellular radiolabel were separated by incubation with the general protease, Pronase.Results: Our results suggest that ferric citrate uptake is mediated by a specific citrate binding site which exhibits a higher affinity for citrate in the presence of iron than in its absence. Citrate was internalised by hepatocytes, with at least 70% being oxidised to CO2 within 15 min. Citrate uptake was pH-dependent, did not require the presence of sodium and increased with increasing iron concentration, Metabolic energy, anion channels, the Na+, K+-ATPase and vesicle acidification do not appear to play a role in uptake of ferric citrate, but functional sulphydryl groups may be involved.Conclusions: The data suggest either that ferric citrate complexes with higher molar ratios of iron to citrate relative to the incubation medium are bound preferentially to the membrane, or that once citrate has delivered its iron to the membrane, the complex dissociates and the components are internalised separately.