ABSTRACT
During the process of phagocytosis, the phagocytic cell consumes oxygen, which it converts largely to superoxide anion (O2 −), then to hydrogen peroxide and, probably, to hydroxyl radical. A large amount of the O2 − is released to the outside of the cell, where it can be detected by its ability to reduce an electron-accepting compound. Although nitroblue tetrazolium has been used in this regard, 1 ferricytochrome c has been particularly useful for this purpose. 2 - 4 The assay developed to measure activity of superoxide dismutase (SOD) 5 was modified first to detect O2 − generated by phagocytosing neutrophils, 2 then for O2 − released by blood monocytes 3 and cultured mononuclear phagocytes (monocytes and macrophages). 4 That the reduction of ferricytochrome c is due to O2 − is demonstrated by the use of SOD. The assay with cells is run with and without SOD, and only SOD-inhibitable reduction of cytochrome c is used to calculate the amount of O2 − released.
