Further studies on the formation of oxygen radicals by potassium superoxide in aqueous medium for biochemical investigations

Potassium superoxide (KO2) forms superoxide anion (O2-) in aqueous medium as measured by the superoxide dismutase (SOD)-inhibitable cytochrome c reduction assay of McCord and Fridovich. The reduction of cytochrome c by O2- formed by KO2 was observed only above pH 7.0 and demonstrated a pH optimum at pH 9.6. SOD was an effective inhibitor of the cytochrome c reduction produced by KO2. Hydroxyl radical scavengers and singlet oxygen quenchers did not interfere with the reduction of cytochrome c by KO2. These data demonstrate that addition of KO2 to aqueous medium is an easy chemical method for the production of O2- in controlled amounts.