Assessment of ferrocytochrome C oxidation by hydrogen peroxide

Abstract

The reduction of ferricytochrome C is commonly employed for the quantitation of O ₂ ⁻ . H₂O₂ arising from the dismutation of O ₂ ⁻ is capable of oxidizing ferrocytochrome C. In order to assess whether this may interfere with O ₂ ⁻ quantitation, the amount of H₂O₂ required for the oxidation of ferrocytochrome C was determined. While H₂O₂ concentrations below 10⁻⁵ M were ineffective, one half of the reduced cytochrome was oxidized by 5×10⁻⁵ M H₂O₂ within 15 min. H₂O₂ in the concentration range at which ferrocytochrome C is oxidized is generated upon interaction of hypoxanthine with xanthine oxidase and upon stimulation of human polymorphonuclear neutrophilic granulocytes by phorbol myristate acetate or the phagocytosis of opsonized zymosan. It is suggested that O ₂ ⁻ quantitation by cytochrome C reduction is routinely performed in the presence of catalase.