INHIBITION OF MAMMARY-GLAND CARCINOGENESIS BY GREEN TEA CATECHINS ANDOTHER NATURALLY-OCCURRING ANTIOXIDANTS IN FEMALE SPRAGUE-DAWLEY RATS PRETREATED WITH 7,12-DIMETHYLBENZ[A]ANTHRACENE

Effects of the naturally occurring antioxidants on mammary gland carci nogenesis were examined in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[a]anthracene (DMBA). Groups of 15-16 7-week-old rats received a 50 mg/kg body weight intra-gastric dose of DMBA, and start ing one week thereafter placed on diet containing 0.4% catechol, 1.0% gamma-oryzanol, 2.0% phytic acid, 1.0% green tea catechins (GTC), 1.0% tannic acid or basal diet alone for 35 weeks. Although the final inci dences and multiplicities of mammary tumors were not significantly dif ferent between DMBA-treated groups, the numbers of survivors in the an tioxidant-treated groups at the end of the experiment at week 36 were significantly higher than in the basal diet group. In particular, the survival rate of the GTC group at 93.8% strongly contrasted with that of only 33.3% for rats on the basal diet. At the end of week 18, when all the animals were still alive, the average size of palpable mammary tumors was significantly smaller in the catechol, phytic acid and cat echins groups. These results indicate that antioxidants, and GTC in pa rticular, inhibit rat mammary gland carcinogenesis after DMBA initiati on.