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Effect of components of green tea extracts, caffeine and catechins on hepatic drug metabolizing enzyme activities and mutagenic transformation of carcinogens

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Please use this identifier to cite or link to this item:http://doi.org/10.14943/jjvr.52.4.185

Title: Effect of components of green tea extracts, caffeine and catechins on hepatic drug metabolizing enzyme activities and mutagenic transformation of carcinogens
Authors: NIKAIDOU, Satoshi Browse this author
ISHIZUKA, Mayumi Browse this author →KAKEN DB
MAEDA, Yutaka Browse this author
HARA, Yukihiko Browse this author
KAZUSAKA, Akio Browse this author
FUJITA, Shoichi Browse this author
Keywords: Cytochrome P450
Green tea
Mutagens
UDP-glucuronyltransferase
Issue Date: Feb-2005
Publisher: The Graduate School of Veterinary Medicine, Hokkaido University
Journal Title: Japanese Journal of Veterinary Research
Volume: 52
Issue: 4
Start Page: 185
End Page: 192
Abstract: Green tea contains catechins and caffeine as major constituents. Treatment of rats with green tea (2.5% w/v) significantly increased 7-ethoxycoumarin O-deethylase (7-ECOD), caffeine N-1demethylase (CN1D) and UDP-glucuronyltransferase (UGT) activities. Treatment with caffeine similarly activated CYP1A2 and related monooxygenases as well as UGT, while treatment with catechins induced UGT activity but not 7-ECOD or CN1D activity. Numbers of benzo[a]pyrene(BP)-induced revertant colonies in an Ames test (mutation assay) with S. typhimurium TA98 as the test strain were markedly larger when BP was preincubated with the liver S-9 (9000×g supernatant of liver homogenate) from green tea-treated rats than when preincubated with that from control rats. In a modified Ames assay system in which UGT was activated by the addition of UDP-glucuronic acid to the preincubation mixture, the numbers of revertant colonies in the assay using liver S-9 from green teatreated rats decreased to a similar level to that in the assay using S-9 from controls. The acceleration of two enzymatic reactions may contribute to the rapid elimination of BP; the first step, the formation of a metabolic intermediate (which is mutagenic) by CYP1A2 and the second, the conjugation of active metabolic intermediates by UGT. We speculated that green tea can reduce the amount of time carcinogens reside in the body and the chance that body tis-prodsues will be exposed to active metabolites of carcinogens thorough rapid elimination due to the simultaneous induction of CYP1A2 and UGT activities.
Type: bulletin (article)
URI: http://hdl.handle.net/2115/877
Appears in Collections:Japanese Journal of Veterinary Research > Volume 52, Number 4

Submitter: 獣医学部図書室

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