1. Inhibition by White Tea of 2-Amino-1-Methyl-6-Phenylimidazo[4,5-b]Pyridine-Induced Colonic Aberrant Crypts in the F344 Rat
- Author
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Meirong Xu, Maria Izquierdo-Pulido, Roderick H. Dashwood, Gayle A. Orner, and Gilberto Santana-Rios
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Male ,Cancer Research ,medicine.medical_specialty ,Glucuronosyltransferase ,Colon ,Medicine (miscellaneous) ,Article ,chemistry.chemical_compound ,Glucuronides ,Cytochrome P-450 Enzyme System ,Western blot ,Cytochrome P-450 CYP1A2 ,Internal medicine ,Cytochrome P-450 CYP1A1 ,medicine ,Animals ,Anticarcinogenic Agents ,Enzyme inducer ,Anticarcinogen ,Glutathione Transferase ,chemistry.chemical_classification ,Nutrition and Dietetics ,2-Amino-1-methyl-6-phenylimidazo(4,5-b)pyridine ,Tea ,biology ,medicine.diagnostic_test ,Sulfates ,Imidazoles ,Biological activity ,Rats, Inbred F344 ,Rats ,Endocrinology ,Enzyme ,Oncology ,Biochemistry ,chemistry ,Enzyme Induction ,Colonic Neoplasms ,biology.protein ,Oxidoreductases ,Precancerous Conditions ,Aberrant crypt foci - Abstract
There is growing interest in the potential health benefits of tea, including the anticarcinogenic properties. We report here that white tea, the least processed form of tea, is a potent inhibitor of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced colonic aberrant crypts in the rat. Male Fischer 344 rats were treated for 8 wk with white tea (2% wt/vol) or drinking water alone, and on alternating days in experimental Weeks 3 and 4 the animals were given PhIP (150 mg/kg body wt p.o.) or vehicle alone. At the end of the study there were 5.65 +/- 0.81 and 1.31 +/- 0.27 (SD) aberrant crypt foci per colon in groups given PhIP and PhIP + white tea, respectively (n = 12, P0.05). No changes were detected in N-acetyltransferase or arylsulfotransferase activities compared with controls, but there was marked induction of ethoxyresorufin O-deethylase, methoxyresorufin O-demethylase, and UDP-glucuronosyltransferase after treatment with white tea. Western blot revealed corresponding increases in cytochrome P-450 1A1 and 1A2 proteins. Enzyme assays and Western blot also revealed induction of glutathione S-transferase by white tea. There was less parent compound and 4'-hydroxy-PhIP but more PhIP-4'-O-glucuronide and PhIP-4'-O-sulfate in the urine from rats given PhIP + white tea than in urine from animals given carcinogen + drinking water. The results indicate that white tea inhibits PhIP-induced aberrant crypt foci by altering the expression of carcinogen-metabolizing enzymes, such that there is increased ring hydroxylation at the 4' position coupled with enhanced phase 2 conjugation. more...
- Published
- 2001
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