Effects of black tea, green tea and wine extracts on intestinal carcinogenesis induced by azoxymethane in F344 rats

We investigated whether polyphenolic extracts from black tea, green tea or red wine affect azoxymethane (AOM)induced intestinal carcinogenesis. Male F344 rats were treated 10 times (1 week apart) with AOM (7.4 mg/kg, s.c.) and then allocated into groups receiving black tea, green tea or red wine extracts mixed in the diet at a dose of 50 mg/kg body weight for 16 weeks. In the rats treated with black tea or wine extracts, there were significantly fewer colorectal tumours than in controls (the mean +/- SE number of tumours/rat was 2.54 +/- 1.6 in controls, 1.54 +/- 1.4 in the black tea group, 3.2 +/- 1.9 in the green tea group and 1.63 +/- 1.6 in the wine extract group). Significantly fewer rats in the black tea and wine extract groups had adenomas than in controls (86%, 59%, 90% and 50% of rats in the control, black tea, green tea and wine extract groups, respectively, had adenomas), The tumours from the black tea group and, to a lesser extent, those from the wine group, had a significantly greater apoptotic index than tumours In controls (mean +/- SE apoptotic index: 2.92 +/- 0.25, 4.13 +/- 0.46, 2.88 +/- 0.30 and 3.72 +/- 0.46 in controls, black tea, green tea or wine extract groups, respectively). Tn contrast, the apoptotic index of the normal mucosa did not vary among groups. These data indicate that black tea and wine extracts, but not green tea extracts, can protect against AOM-induced colon carcinogenesis by a mechanism probably involving increased apoptosis in tumours.