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Long Term Effects of Benzo(a)pyrene on the Activity of NAD(P)H:Quinone Reductase in the Forestomach and Glandular Stomach of ICR/Ha Mice¹

Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota 55455

The present study is part of an effort to identify biomarkers for various stages of preneoplasia. For this purpose, quinone reductase [NAD(P)H:quinone oxidoreductase, EC 1.6.99.2] (QR) activity in the forestomach of ICR/Ha mice was investigated at successive time points during benzo(a)pyrene (BP)-induced carcinogenesis. Six mg of BP in 0.2 ml of cottonseed oil or cottonseed oil alone were given orally twice a week for 2 weeks to female ICR/Ha mice. Ten mice from each group were sacrificed sequentially at 2-week intervals, and the QR activity was determined in the forestomach, a target tissue for BP carcinogenicity, and also in the glandular stomach, a non-target tissue. QR was significantly increased in the cytosolic, microsomal, and mitochondrial fractions of the forestomach of BP-treated animals. There was no significant increase in this activity in any fraction of the glandular stomach. The increases in QR activity in the subcellular fractions of the forestomach from BP-treated animals showed a two-surge pattern. The first was manifested at 2 weeks. The second, found at week 6, continued throughout the remaining course of the experiment. To our knowledge, the time course of changes in QR activity in the three subcellular fractions of mouse forestomach during BP carcinogenesis has not been demonstrated previously.

¹ Supported by American Cancer Society Grant SIG-5. This study is a part of the Ph.D. thesis of A. D. J. in Pathobiology at the Graduate School of the University of Minnesota.

² To whom requests for reprints should be addressed.

Received 8/11/89. Revised 12/ 7/89.