[Effect of tea polyphenols and tea pigments on inducing the activity of phase II detoxicating enzymes and on the chemoprevention of liver precancerous lesions].

In order to elucidate the chemoprevention mechanism of tea, the regulative effect of tea polyphenols and tea pigments on phase II enzyme, glutathions S-transferase (GST) activity and its isoenzymes in Wistar rat were studied. Rat liver precancerous lesions were initiated with diethylnitrosamine (DEN), promoted with partial hepatectomy and carbon tetrachloride. The rats were killed after 8 weeks of treatment. Liver cytosol GST activities were tested. The GST 1-1, 1-2, 3-3 and Pi isoenzymes were detected with Western Blot method. The results showed that the activities of GST increased greatly in the tea polyphenol and tea pigment groups, while the activities were decreased in positive control group. Both tea polyphenold and tea pigments increased the activities of classes GST alpha (GST1-1, 1-2) and GST mu(GST3-3). The increase of GST alpha was more in tea polyphenol group, and the increase of GST mu was more in tea pigment group. Both tea polyphenols and tea pigments inhibited the over expression of GST Pi in the rats treated with DEN/PH/CCl4. The study indicated that tea polyphenols and tea pigments modulated phase II enzymes effectively, thus inhibited the occurrence and development of the precancerous lesions of rat liver.