STIMULATION OF MICROSOMAL CHEMILUMINESCENCE BY FERRITIN

The ability of ferritin to catalyze rat liver microsomal chemiluminesc ence was determined in the absence and presence of the redox cycling a gent paraquat, and with either NADPH or NADH as reductant. Microsomal chemiluminescence was used as a index of lipid peroxidation. In the ab sence of added ferritin, NADPH-dependent microsomal light emission was 4-fold greater than the NADH-dependent reaction, and was not sensitiv e to superoxide dismutase, catalase or DMSO. Ferritin stimulated NADPH -, but not NADH-dependent chemiluminescence in a time- and concentrati on-dependent manner. The stimulation by ferritin was completely sensit ive to superoxide dismutase, but not to catalase or DMSO, suggesting t he requirement for superoxide to mobilize iron from ferritin. An iron ligand was not required for the stimulation by ferritin; the addition of certain ligands such as EDTA, DETAPAC or desferrioxamine resulted i n inhibition of the stimulation by ferritin. Paraquat potentiated the effect of ferritin on microsomal chemiluminescence with NADPH as cofac tor and was weakly stimulatory with NADH. The potentiation by paraquat plus ferritin was prevented by superoxide dismutase and was further e levated by ligands such as ATP. Chemiluminescence proved to be a more sensitive parameter than production of thiobarbituric acid-reactive co mponents to evaluate the stimulation of oxygen radical production by i ron released from ferritin, in the absence or in the presence of paraq uat.