EFFECTS OF GREEN TEA CATECHINS IN A RAT MULTIORGAN CARCINOGENESIS MODEL

The effects of dietary administration of green tea catechins (GTC) wer e examined using a multi-organ carcinogenesis model. Groups of 15 F344 male rats were initially treated with a single i.p. administration of 100 mg/kg body wt N-diethyl-nitrosamine, 4 i.p. administrations of 20 mg/kg body wt N-methylnitrosourea, 4 s.c. doses of 40 mg/kg body wt 1 ,2-dimethylhydrazine, together with 0.05% N-butyl-N-(4-hydroxybutyl)ni trosamine for 2 weeks and then 0.1% 2,2'-dihydroxy-di-n-propylnitrosam ine for 2 weeks, both in the drinking water, for a total initiation pe riod of 4 weeks. GTC in the diet, at doses of 1.0 or 0.1%, was adminis tered from 1 day before and during carcinogen exposure, after carcinog en exposure or both during and after carcinogen exposure. Further grou ps of animals were treated with carcinogen, 1% GTC or basal diet alone as controls. All animals were killed at the end of week 36, and all m ajor organs examined histopathologically. The numbers of small intesti nal tumors (adenomas and carcinomas) per rat were significantly reduce d in the groups treated with 1% GTC during (0.13 +/- 0.35) and after c arcinogen exposure (0.31 +/- 0.48) and in those receiving 1% and 0.1% GTC both during and after carcinogen exposure (0.14 +/- 0.36, 0.46 +/- 0.97 respectively) as compared with the carcinogen alone group (1.07 +/- 1.21). On the other hand, numbers of glutathione S-transferase pla cental form positive liver foci per cm2 were slightly but significantl y increased in the groups treated with 1 and 0.1% GTC during carcinoge n exposure, 1% GTC after carcinogen exposure and 1% GTC both during an d after carcinogen exposure. The results indicated that while GTC inhi bits small intestinal carcinogenesis it slightly enhances hepatocarcin ogenesis in a dose dependent manner when applied both during and after carcinogen exposure.