Evidence for the extracellular reduction of ferricyanide by rat liver. A trans-plasma membrane redox system.
Evidence for the extracellular reduction of ferricyanide by rat liver. A trans-plasma membrane redox system.
复制标题
大鼠肝脏细胞外铁氰化物还原的证据。
DOI：
10.1042/bj2000565
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发表时间：
1981
期刊：
影响因子：
--
通讯作者：
Grebing,C
中科院分区：
文献类型：
--
作者：
Clark,MG;Partick,EJ;Patten,GS;Crane,FL;Löw,H;Grebing,C
1.研究了离体灌注大鼠肝脏和离体大鼠肝细胞对铁氰化物的还原作用。 2.铁氰化物被灌注的肝脏以每克肝脏0.22μmol/min的线性速率还原为亚铁氰化物。铁氰化物不被肝脏吸收，并且铁氰化物+亚铁氰化物的灌注液浓度在整个灌注过程中保持恒定。来自不含铁氰化物灌注的肝脏的灌注液样品不会减少铁氰化物。 3.分离的肝细胞以双相方式还原铁氰化物。初始速率为每克细胞 2.3μmol/分钟，持续约 1 分钟。 3分钟，源自低亲和力位点（表观Km>1.3mm）。在余下的孵育过程中，二级速率保持在每克细胞 0.29μmol/min 的水平，并且源自较高亲和力位点（表观 Km0.13mm）。细胞的破坏导致低亲和力率增加和高亲和力率下降。 4.亚铁氰化物被分离的肝细胞氧化，但不被灌注的肝脏氧化。肝细胞对亚铁氰化物氧化的表观Km为1.3mm。 5.在1mm-KCN存在下，氧化细胞色素c被分离的肝细胞还原，但还原速率低于铁氰化物的还原速率。 6.检查了完整肝细胞和灌注肝脏的铁氰化物还原活性的特性。仅存在于细胞和破碎细胞制剂中的低亲和力被1μm-鱼藤酮和0.5mm-亚铁氰化物抑制，并被0.1mm-KCN刺激。线粒体底物琥珀酸也刺激了这一速率。灌注的肝脏仅表现出对铁氰化物还原的高亲和力活性。这种活性也存在于肝细胞中，并且不受鱼藤酮、抗霉素 A、KCN、NaN3、orp-羟基汞苯甲酸盐的影响，但受到 2.6mm-CaCl2、2-庚基-4-羟基喹啉-N-氧化物和亚铁氰化物的抑制。总体而言，这些结果与肝脏跨质膜氧化还原系统的发生一致，该系统将细胞外铁氰化物还原为亚铁氰化物。该还原过程显示出与分离的肝质膜中发现的 NADH：铁氰化物氧化还原酶相似的特性，但与线粒体不同。
1. Reduction of ferricyanide by the isolated perfused rat liver and by isolated rat hepatocytes was studied. 2. Ferricyanide was reduced to ferrocyanide by the perfused liver at a linear rate of 0.22μmol/min per g of liver. Ferricyanide was not taken up by the liver and the perfusate concentration of ferricyanide+ferrocyanide remained constant throughout the perfusion. Perfusate samples from livers perfused without ferricyanide did not reduce ferricyanide. 3. Isolated hepatocytes reduced ferricyanide in a biphasic manner. The initial rate of 2.3μmol/min per g of cells proceeded for approx. 3min and derived from low-affinity sites (apparentKm>1.3mm). The secondary rate of 0.29μmol/min per g of cells was maintained for the remainder of the incubation and derived from higher affinity sites (apparentKm0.13mm). Disruption of the cells resulted in an increase in the low-affinity rate and a decrease in the high-affinity rate. 4. Ferrocyanide was oxidized by isolated hepatocytes but not by perfused liver. The apparentKmfor ferrocyanide oxidation by hepatocytes was 1.3mm. 5. Oxidized cytochromecwas reduced by isolated hepatocytes in the presence of 1mm-KCN but at a rate less than that of the reduction of ferricyanide. 6. Properties of the ferricyanide-reducing activities of intact hepatocytes and the perfused liver were examined. The low-affinity rate, present only in cell and broken cell preparations, was inhibited by 1μm-rotenone and 0.5mm-ferrocyanide, and stimulated by 0.1mm-KCN. The mitochondrial substrate, succinate, also stimulated this rate. The perfused liver showed only a high-affinity activity for ferricyanide reduction. This activity was also present in liver cells and was unaffected by rotenone, antimycin A, KCN, NaN3, orp-hydroxymercuribenzoate but was inhibited by 2.6mm-CaCl2, 2-heptyl-4-hydroxyquinoline-N-oxide and ferrocyanide. Overall, these results are consistent with the occurrence of a trans-plasma membrane redox system of liver that reduces extracellular ferricyanide to ferrocyanide. The reduction process shows properties which are similar to that of the NADH:ferricyanide oxidoreductase found in isolated liver plasma membranes but different from that of mitochondria.