Radical production in liver mitochondria by peroxidic tumor promoters

Eleven peroxides have been tested to determine if there is a correlation between tumor-promoting activity and the ability to stimulate radical production in mitochondria. When non-respiring rat liver mitochondria are treated with these peroxidic compounds in the presence of DMPO, ESR signals are observed from the spin trapping of carbon- and oxygen-centered radicals in the case of 4 of the 7 peroxides that are known to be tumor promoters. Enhancement of carbon-centered radical production is observed in the presence of respiratory substrate. Thus there does not appear to be a correlation between tumor-promoting activity of peroxidic compounds and radical production in mitochondria. Oxidants can act as promoters either by 1- or 2-electron oxidation pathways; both types of mechanisms may be inhibited by antioxidants, which can scavenge either radicals or electrophiles.