Abstract
Antioxidants were found to inhibit the mixed-function oxidation of benzo(a)pyrene in several tissues of untreated and 3-methylcholanthrene-pretreated rats. The enzyme systems in the liver, kidney and stomach were much more susceptible to inhibition than those in the lung, adrenal, colon and small intestine. In all tissues except the stomach it was found that 3-methylcholanthrene pretreatment led to a decrease in inhibition of benzo(a)pyrene 3-hydroxylase activity. It is suggested that antioxidants exert their protective effect against cancer by inhibiting the formation of carcinogenic metabolites. Of the various steroids tested, only 17 beta-oestradiol and oestrone were significantly inhibitory in most tissues. Cholesterol was found to increase benzo(a)pyrene 3-hydroxylase activity in the gastrointestinal tract.