Haem transport to the liver by haemopexin. Receptor-mediated uptake with recycling of the protein.
Haem transport to the liver by haemopexin. Receptor-mediated uptake with recycling of the protein.
复制标题
血红素通过血红素结合蛋白转运至肝脏。
DOI：
10.1042/bj1820047
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发表时间：
1979
期刊：
影响因子：
--
通讯作者：
W. Morgan
中科院分区：
文献类型：
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作者：
A. Smith;W. Morgan
大鼠静脉注射[（59）Fe]血红素-（125）I标记的血红素结合蛋白复合物（700 pmol/只）后，迅速地与肝脏结合。这两种同位素显示出不同的积累模式。肝脏（125）I标记的血红素结合蛋白在注射后10分钟达到最大值（20+/-4.9pmol/g肝脏），然后在注射脱辅基蛋白后2小时下降至低值（约3 pmol/g肝脏）。相反，[（59）Fe]血红素在肝脏中积累至少2 h。在血红素运输的2小时内，溶血素没有发生广泛的蛋白水解，如酸沉淀（98%）和特异性抗血清沉淀（92%）以及电泳所示。此外，只有1-2%的剂量位于肝外组织中，并且没有显著的（125）I或（59）Fe的尿排泄。在10分钟时肝脏摄取是饱和的，在9 nmol/大鼠的剂量下达到200 pmol的血红素结合蛋白/g肝脏和350 pmol的血红素/g肝脏，而载脂蛋白的摄取是剂量的3-5%。这表明血-血结合蛋白与肝脏的相互作用是一种特异性受体介导的过程。该复合物可能通过蛋白质部分相互作用，因为血红素类似物中血红素和次血红素不影响蛋白质与肝脏的关联，但血红素结合蛋白的种类会影响。注射后5分钟，肝脏中蛋白质的量增加，顺序为：人>兔>大鼠，血红素摄取持续增加。对于大鼠和兔，在相同的蛋白质浓度（即180- 200 pmol/g肝脏）下达到血红素结合蛋白饱和，表明不同的蛋白质种类与共同的受体结合。我们建议，血红素结合蛋白运输血红素到肝脏的一个特定的受体介导的过程，然后返回到循环。
Rat [(59)Fe]haem-(125)I-labelled haemopexin complexes (700pmol/rat) associate rapidly and exclusively with the liver after intravenous injection into anaesthetized rats. The two isotopes exhibit different patterns of accumulation. Liver (125)I-labelled haemopexin is maximum 10min after injection (20+/-4.9pmol/g of liver) and then declines by 2h to the low values (about 3pmol/g of liver) seen after injection of the apoprotein. In contrast, [(59)Fe]haem accumulates in the liver for at least 2h. Haemopexin undergoes no extensive proteolysis during 2h of haem transport as shown by precipitation with acid (98%) and specific antiserum (92%) and by electrophoresis. Moreover, only 1-2% of the dose is located in extrahepatic tissues, and there is no significant urinary excretion of either (125)I or (59)Fe. Hepatic uptake at 10min is saturable, reaching 200pmol of haemopexin/g of liver and 350pmol of haem/g of liver at a dose of 9nmol/rat, whereas uptake of the apoprotein is 3-5% of the dose. This suggests that the interaction of haem-haemopexin with the liver is a specific receptor-mediated process. The complex probably interacts via the protein moiety, since the haem analogues mesohaem and deuterohaem do not affect association of the protein with the liver but the species of haemopexin does. Increasing amounts of protein are associated with the liver 5min after injection in the order: human>rabbit>rat, and haem uptake is consistently increased. For both rat and rabbit haemopexin saturation is reached at the same concentration of protein, i.e. 180-200pmol/g of liver, indicating that the different protein species bind to a common receptor. We propose that haemopexin transports haem to the liver by a specific receptor-mediated process and then returns to the circulation.