Effect of diet and route of administration on the DNA binding of aflatoxin B1 in the rat

The effects of dietary Brussels sprouts and indole-3-carbinol (I3C) on xenobiotic-metabolizing enzyme activities and hepatic aflatoxin B1 (AFB1)-DNA binding were determined in rats. Animals were dosed intraperitoneally (i.p.) or intragastrically (i.g.) with [3H]AFB1 and killed 2 (i.p.) or 3 (i.g.) h later. Brussels sprouts caused a significant (P less than 0.01) 50-60% decrease in hepatic AFB1-DNA binding, and increased hepatic and intestinal glutathione S-transferase (GST) activities. Hepatic mono-oxygenase (AHH and ECD) activities were not altered in sprouts-fed rats, but greater than 2-fold increases in intestinal AHH and ECD activities were found. Although I3C increased intestinal AHH and ECD activities similarly to Brussels sprouts, I3C did not significantly decrease AFB1 binding, nor did it increase hepatic or intestinal GST activity. Route of administration did not alter the percentage inhibition of binding in comparison to control rats in either treatment group, suggesting that the small intestine may not play a significant role in the metabolism of AFB1. In a second experiment, rats were dosed either i.p. or i.g. with [3H]AFB1 and killed 2, 6, 12, 24 or 48 h later. Hepatic AFB1-DNA binding and tissue radioactivity levels were determined. Brussels sprouts once again significantly (P less than 0.001) decreased hepatic AFB1-DNA binding. Route of administration of the carcinogen did not affect DNA binding over time in sprouts-fed animals, confirming our previous results.