Reinke L A, Moore D R, Rau J M, McCay P B
Department of Pharmacology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
Arch Biochem Biophys. 1995 Feb 1;316(2):758-64. doi: 10.1006/abbi.1995.1101.
The phosphate buffer concentration used in spin trapping experiments with liver microsomes markedly influenced rates of free radical formation from ethanol and dimethylsulfoxide, but not from carbon tetrachloride. Effects of phosphate concentration on ethanol radical formation were abolished by addition of deferoxamine or bathophenanthrolene, indicating that an iron-phosphate complex might be involved. High concentrations of phosphate stimulated rates of microsomal Fe+3 reduction and facilitated the mobilization of microsomal nonheme iron, but had little effect on a variety of microsomal monooxygenase enzyme activities. Although microsomal oxygen utilization and superoxide production were relatively unaffected by phosphate, hydrogen peroxide concentrations were markedly decreased in the presence of high concentrations of phosphate. Taken together, the data suggest that a ferric-phosphate complex may be enzymatically reduced by microsomal enzymes and NADPH. Reoxidation of ferrous ion is nonenzymatically promoted by phosphate and/or H2O2 produced by the microsomes. During the process of reoxidation, one or more oxidizing intermediates may be formed which initiate secondary free radical reactions. Although the reactivity of the intermediate(s) is similar to that of the hydroxyl radical, no spin trapping evidence was obtained to support this assignment.
在使用肝微粒体进行自旋捕获实验时，磷酸盐缓冲液的浓度对乙醇和二甲基亚砜产生自由基的速率有显著影响，但对四氯化碳产生自由基的速率没有影响。添加去铁胺或二氮杂菲可消除磷酸盐浓度对乙醇自由基形成的影响，这表明可能涉及铁 - 磷酸盐复合物。高浓度的磷酸盐刺激微粒体Fe +3还原速率并促进微粒体非血红素铁的动员，但对多种微粒体单加氧酶活性影响不大。虽然微粒体氧利用和超氧化物产生相对不受磷酸盐影响，但在高浓度磷酸盐存在下，过氧化氢浓度显著降低。综合来看，数据表明磷酸铁复合物可能被微粒体酶和NADPH酶促还原。亚铁离子的再氧化由磷酸盐和/或微粒体产生的H2O2非酶促促进。在再氧化过程中，可能形成一种或多种氧化中间体，引发次级自由基反应。尽管中间体的反应性与羟基自由基相似，但未获得自旋捕获证据来支持这一归属。
