INHIBITION OF N-METHYL-N'-NITRO-N-NITROSOGUANIDINE-INDUCED CARCINOGENESIS BY (-)-EPIGALLOCATECHIN GALLATE IN THE RAT GLANDULAR STOMACH

Recently, an epidemiological study showed a lower risk of gastric canc er among people who consume a large amount of green tea. (-)-Epigalloc atechin gallate (EGCG), one of the main constituents of green tea, inh ibited tumor promotion by teleocidin in a two-stage carcinogenesis exp eriment with the use of mouse skin, The inhibitory effect of EGCG on N -methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis of t he glandular stomach in rats was examined, The percentage of tumor-bea ring rats in the group treated with MNNG plus EGCG was 31%, compared t o 62% in the MNNG group, The difference was statistically significant (P < 0.05). To assess the effect of p.o. administration of EGCG, the g astric mucosal cellular kinetics was examined with the use of the brom odeoxyuridine labeling index, ornithine decarboxylase activity, and ti ssue polyamine levels. The labeling index of the EGCG treatment group decreased significantly (P < 0.05) compared to the EGCG plus MNNG trea tment group, The ornithine decarboxylase activity and tissue spermidin e levels were also decreased, On the other hand, the tissue putrescine and spermine levels were partly increased, These findings suggest tha t EGCG inhibits the cellular kinetics of the gastric mucosa during the promotion stage of MNNG-induced gastric carcinogenesis, EGCG may be u seful in preventing gastric carcinogenesis, Moreover, EGCG may be appl ied clinically without any harmful effects and at a low cost.