Inhibitory effects of alpha- and beta-carotene on croton oil-induced or enzymatic lipid peroxidation and hydroperoxide production in mouse skin epidermis.

1. The effects of carotenes (alpha- and beta-) on edema, MDA contents and peroxidizability of croton oil-treated mouse skin epidermis, hydroperoxide production and enzymatic lipid peroxidation of epidermal homogenates were studied. Edema was determined as ear punch weight and the intensity of lipid peroxidation was measured using malondialdehyde formation. 2. Carotenes (alpha- and beta-) significantly suppressed edema formation, hydroperoxide production, lipid peroxidation caused by croton oil, Fe + 3-ADP/NADPH or paraquat/NADPH in vivo as well as in vitro. 3. These results indicate that both alpha- and beta-carotene have chemopreventive effects on croton oil-induced tumor promotion in skin tumorigenesis by scavenging oxygen free radicals, indirectly determined as carotene inhibition of lipid peroxidation and hydroperoxide formation.