A comparison of whole wheat, refined wheat and wheat bran as inhibitors ofheterocyclic amines in the Salmonella mutagenicity assay and in the rat colonic aberrant crypt focus assay

Refined wheat, unrefined whole wheat, and wheat bran were studied for their ability to protect against heterocyclic amines (HCAs) in vitro and in vivo . Wheat bran, which binds HCAs in vitro, as well as refined wheat and unref ined whole wheal, inhibited the mutagenic activities of 2-amino-3-methylimi dazo[4,5-f]quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) when they were co-incubated and the supernatant (minus grain) was added to the Salmon ella assay. The water-soluble fraction alone from refined and unrefined whe at, but not bran, also inhibited against these mutagens in vitro. In vivo, AIN-93G diets containing refined wheat or unrefined wheat were examined For their ability to inhibit IQ-induced colonic aberrant crypt Foci (ACF) in t he Fischer 344 rat. A slight increase in the number of AC/ACF (aberrant cry pts/ACF) was seen after 16 weeks in rats treated post-initiation with refin ed wheat (P < 0.05), and fewer foci with two or three aberrant crypts (ACF- 2) were found in rats given unrefined whole wheat post-initiation compared with animals treated with the same diet during the initiation phase (P < 0. 05). There was no significant difference in the profile of IQ urinary metab olites or excretion of promutagens 0-48 h after carcinogen dosing, and grai ns had no effect on hepatic cytochrome P4501A1 (CYP1A1), CYP1A2, aryl sulfo transferase or N-acetyltransferase activities; however, a slightly higher U DP-glucuronosyl transferase activity was observed in rats fed unrefined whe at compared with refined wheat diets (P < 0.05). Thus, despite their antimu tagenic activities in vitro, only marginal effects were seen with refined a nd unrefined wheat in vivo with respect to hepatic enzyme activities, carci nogen metabolism and IQ-induced ACF in the rat colon. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.