Effect of dietary selenium levels on 7,12-dimethylbenzanthraceneinduced mouse mammary tumorigenesis. Carcinogenesis

The effect of dietary selenium levels on 7,12-dimethylbenz-anthracene (DMBA)-induced mammary tumors was examin-ed in mice fed a semi-purified diet (20 % casein, 50 % sucrose, 5 % corn oil). (C57BLxDBA/2f)F1 (BD2Fi) female mice were fed diets containing 0.2, 0.5, 1.0 and 2.0 p.p.m. selenium starting at 7 weeks of age. The mammary tumor incidence was 56, 30, 25 and 16%, respectively, after the mice were on the diet for 9 months. In a second experiment, BALB/cV female mice were fed diets containing 0.2 and 2.0 p.p.m. selenium. After 9 months on the diet, the mammary tumor incidence was 39 and 7%, respectively. Both strains of mice grew equally well on the 0.2 and 2.0 p.p.m. selenium diets in-dicating that the highest dietary selenium level was compati-ble with normal growth. The selenium cpncentration and selenium dependent-glutathione peroxidase (GSH-Px) activi-ty of mammary glands from control BD2F, mice fed 0.2,1.0 and 2.0 p.p.m. dietary selenium was examined at 8, 9 and 10 months of age. As in previous experiments in adult BALB/c mice, the concentration of mammary gland selenium, but not GSH-Px activity, increased with increasing levels of dietary selenium. These results document that nutritional levels of dietary selenium (0.5 p.p.m. Se) as well as non-toxic higher levels (2.0 p.p.m. Se) inhibit DMBA-induced mammary tumorigenesis