Effects of brussels sprouts, indole 3-carbinol and phenobarbital on xenobiotic metabolism and in vivo DNA binding of aflatoxin B1 in the rat

Cruciferous vegetables have been shown to be potent inducers of xenobiotic-metabolizing enzymes in the rat and this may offer protection against chemical carcinogenesis. Adult, male, SD rats were fed on purified diets supplemented with 25% freeze-dried Brussels sprouts or 250 ppm idole 3-carbinol (I3C) for 2 weeks, or given phenobarbital (PB, 1 mg/ml) in the drinking water for 7 days prior to killing. Brussels sprouts caused a 50% decrease (p < 0.001) in the in vivo binding of [3H] aflatoxin B1 (AFB1) to liver DNA, and increased intestinal and hepatic glutathione S-transferase (GST) activity. Hepatic monooxygenase activity was not altered in this group but greater than 2-fold increases in intestinal aryl hydrocarbon hydroxylase (AHH) and ethoxycoumarin O-deethylase (ECD) activities were found. I3C did not decrease AFB1 binding, nor did it increase hepatic or intestinal GST activity. I3C did increase both intestinal AHH and ECD activities. PB treatment significantly decreased AFB1 binding by 60%, and significantly elevated hepatic but not intestinal GST activity. Hepatic AHH and ECD activities were also elevated in this group, while intestinal AHH and ECD activities were decreased. These results emphasize the importance of GST activity in the detoxification of AFB1 and suggest a less important role for intestinal monooxygenase activity in the metabolism of this hepatocarcinogen