Inhibition by the protein ceruloplasmin of lipid peroxidation stimulated by an Fe³⁺—ADP—adriamycin complex

Self-reduction of an Fe3+-ADP-adriamycin complex under anaerobic conditions and reduction of ferricytochrome c by the complex under aerobic conditions were strongly inhibited by ceruloplasmin, but not by superoxide dismutase or albumin at the same protein concentration. Ceruloplasmin, a protein with ferroxidase activity, is able to catalyse oxidation of Fe2+ to the ferric state. The inhibitory activity of ceruloplasmin towards reactions stimulated by the complex suggests that Fe2+ is formed during the self-reduction process. As expected, the Fe3+-ADP-adriamycin complex stimulated lipid peroxidation in which the Fe2+ moiety was implicated. This stimulation was again effectively prevented by ceruloplasmin but not by superoxide dismutase.