Inhibitory effects of tea polyphenols and tea pigments on liver precancerous lesions in rats
Gong, Y.; Han, C.; Chen, J.
Wei Sheng Yan Jiu 28(5): 294-296
1999
ISSN/ISBN: 1000-8020 PMID: 12712701 Document Number: 505750
A liver precancerous model in rats was established with diethylnitorsamine(DEN) injected intraperitoneally as initiator and promoted by partial hepatectomy and injection of CCl4. The model was used to study the chemopreventive effect of tea polyphenols and tea pigments. A water solution of 0.1% tea polyphenols or tea pigments was given to Wistar rats as drinking water during the 56-day experiment period. A stable and sensitive early marker of liver cancer--GST-Pi positive foci or nodule was measured by a immunohistochemical method. Both tea polyphenols and tea pigments decreased the density and area of the GST-Pi foci. The expression of GST-Pi mRNA in chemical induced precancerous liver tissue was measured by Northern Blotting technique, and the expression of GST-Pi isoenzyme in liver tissue was detected by Western Blotting method. The results showed that both tea polyphenols and tea pigments effectively reduced the GST-Pi expression at both transcription and translation level. It is concluded that the inhibition of tea polyphenols and tea pigments on GST-Pi overexpression induced by chemical carinogen may be one of the mechanisms of their inhibition on the occurrence and progression of liver precancerous lesions in rats.