| Environmental Health Issues Herman A. J. Schut Department of Pathology, Medical College of Ohio, Toledo, Ohio Abstract
In numerous in vivo systems it has been shown that diets high in menhaden oil (a fish oil high in w-3 fatty acids) can inhibit the carcinogenic process. In the present study, we have assessed the effects of a diet containing menhaden oil on 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) -DNA adduct formation in target tissues of the male Fischer 344 rat. Young adult male Fischer 344 rats were maintained on either a) an AIN-76A diet containing 5% corn oil, b) an isocaloric AIN-76A diet modified to contain 2% corn oil and 19% menhaden oil (MO diet) , or c) a regular laboratory rodent diet (chow diet) for 6 weeks prior to receiving a single oral dose of 10 or 50 mg IQ/kg. Groups of four animals were killed 1 or 6 days after IQ administration. Using 32P-postlabeling assays, IQ-DNA adducts were isolated and quantitated in the liver, small intestine, and large intestine. Adduct patterns were similar in all cases. Adduct levels, expressed as relative adduct labeling values (RAL x 107) , were related to dose in all three tissues, with liver levels up to 10-fold higher than the large intestine and up to 20-fold higher than the small intestine. On day one, liver adduct levels in animals on the AIN-76A diet were similar to those in animals on the chow diet, but those in animals on the MO diet were approximately 2-fold lower. On day six, these differences were much lower, probably as a result of the more efficient removal of liver adducts in animals on AIN-76A or chow diets. In the intestines, removal of adducts in animals on either AIN-76A or MO diet was slower than that in the liver, while that in animals on the chow diet was similar to that in the liver. While dietary MO is generally thought to inhibit experimental tumorigenesis at the promotional stage, the present results show that MO diets may also inhibit the initiation process by inhibiting the initial rate of IQ-DNA adduct formation. It also appears, however, that MO diets may impair the process of adduct removal. --Environ Health Perspect 102(Suppl 6) :57-60 (1994) Key words: 2-amino-3-methylimidazo[4, 5-f]quinoline, IQ, 32P-postlabeling, DNA adducts, menhaden oil, chemoprevention, carcinogenesis, heterocyclic amines, food mutagens
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