Bérczi A, Sizensky J A, Crane F L, Faulk W P
Center for Reproduction and Transplantation Immunology, Methodist Hospital of Indiana, Indianapolis 46202.
Biochim Biophys Acta. 1991 Apr 9;1073(3):562-70. doi: 10.1016/0304-4165(91)90231-5.
This paper critically examines the redox activity of K562 cells (chronic myelogenous leukemia cells) and normal peripheral blood lymphocytes (PBL). Ferricyanide reduction, diferric transferrin reduction, and ferric ion reduction were measured spectrophotometrically by following the time-dependent changes of absorbance difference characteristic for ferricyanide disappearance and for the formation of ferrous ion:chelator complexes. Bathophenanthroline disulfonate (BPS) and ferrozine (FZ) were used to detect the appearance of ferrous ions in the reaction mixtures when diferric transferrin or ferric reduction was studied. Special attention was devoted to the analysis of time-dependent absorbance changes in the presence and absence of cells under different assay conditions. It was observed and concluded that: (i) FZ was far less sensitive and more sluggish than BPS for detecting ferrous ions at concentrations commonly used for BPS; (ii) FZ, at concentrations of at least 10-times the commonly used BPS concentrations, seemed to verify the results obtained with BPS; (iii) ferricyanide reduction, diferric transferrin reduction and ferric ion reduction by both K562 cells and peripheral blood lymphocytes did not differ significantly; and (iv) earlier values published for the redox activities of different cells might be overestimated, partly because of the observation published in 1988 that diferric transferrin might have loosely bound extra iron which is easily reduced. It is suggested that the specific diferric transferrin reduction by cells might be considered as a consequence of (i) changing the steady-state equilibrium in the diferric transferrin-containing solution by addition of ferrous ion chelators which effectively raised the redox potential of the iron bound in holotransferrin, and (ii) changing the steady-state equilibrium by addition of cells which would introduce, via their large and mostly negatively charged plasma membrane surface, a new phase which would favor release and reduction of the iron in diferric transferrin by a ferric ion oxidoreductase. The reduction of ferricyanide is also much slower than activities reported for other cells which may indicate reduced plasma membrane redox activity in these cells.
本文批判性地研究了K562细胞（慢性粒细胞白血病细胞）和正常外周血淋巴细胞（PBL）的氧化还原活性。通过跟踪铁氰化物消失和亚铁离子：螯合剂复合物形成所特有的吸光度差异随时间的变化，用分光光度法测量铁氰化物还原、二价铁转铁蛋白还原和铁离子还原。在研究二价铁转铁蛋白或铁还原时，用4,7-二苯基-1,10-菲啰啉二磺酸（BPS）和亚铁嗪（FZ）检测反应混合物中亚铁离子的出现。特别关注在不同测定条件下有细胞和无细胞时随时间变化的吸光度变化分析。观察并得出以下结论：（i）在BPS常用浓度下，FZ检测亚铁离子的灵敏度远低于BPS，且反应更迟缓；（ii）FZ浓度至少为BPS常用浓度的10倍时，似乎能验证用BPS获得的结果；（iii）K562细胞和外周血淋巴细胞的铁氰化物还原、二价铁转铁蛋白还原和铁离子还原没有显著差异；（iv）先前发表的不同细胞氧化还原活性的值可能被高估了，部分原因是1988年发表的观察结果，即二价铁转铁蛋白可能有松散结合的额外铁，很容易被还原。有人提出，细胞特异性的二价铁转铁蛋白还原可能是由于：（i）加入亚铁离子螯合剂改变含二价铁转铁蛋白溶液中的稳态平衡，这有效地提高了全转铁蛋白中结合铁的氧化还原电位；（ii）加入细胞改变稳态平衡，细胞通过其大多带负电荷的大质膜表面引入一个新相，这将有利于二价铁转铁蛋白中的铁被铁离子氧化还原酶释放和还原。铁氰化物的还原也比其他细胞报道的活性慢得多，这可能表明这些细胞的质膜氧化还原活性降低。
