Document Detail

Selective induction of rat hepatic CYP1 and CYP4 proteins and of peroxisomal proliferation by green tea.
MedLine Citation:
PMID:  7955108     Owner:  NLM     Status:  MEDLINE    
Rats were exposed to freshly prepared aqueous extracts of green tea (2.5% w/v) as the sole source of drinking water for 4 weeks. Hepatic cytochrome P450 activity was determined using chemical probes, showing selectivity for particular isoforms, and by immunoblot analysis employing polyclonal antibodies. Exposure to green tea gave rise to increases in the O-demethylation of methoxyresorufin and, to a lesser extent, in the dealkylations of ethoxyresorufin and pentoxyresorufin. An increase was also seen in lauric acid hydroxylation but, in contrast, the N-demethylation of erythromycin was inhibited. p-Nitrophenol oxidase activity was unaffected by the same treatment. Immunoblot analysis revealed increases in the apoprotein levels of CYP1A2 and CYP4A1 following treatment with green tea. A significant increase was also noted in the CN(-)-insensitive palmitoyl CoA oxidation and this was paralleled by an increase in the levels of the peroxisomal trifunctional protein determined immunologically. Hepatic S9 and microsomal preparations from tea-treated animals were more effective than controls in activating 2-amino-3-methylimidazol[4,5-f]quinoline and 2-aminoanthracene to mutagens in the Ames test. When N-nitrosopyrrolidine served as the promutagen, tea did not influence its mutagenicity when isolated microsomes comprised the activation system but a significant inhibition was observed when hepatic S9 was used. The above findings are discussed within the context of the established anticarcinogenic and anti-mutagenic properties of green tea.
A Bu-Abbas; M N Clifford; R Walker; C Ioannides
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Carcinogenesis     Volume:  15     ISSN:  0143-3334     ISO Abbreviation:  Carcinogenesis     Publication Date:  1994 Nov 
Date Detail:
Created Date:  1994-12-22     Completed Date:  1994-12-22     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  8008055     Medline TA:  Carcinogenesis     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  2575-9     Citation Subset:  IM    
Division of Toxicology, School of Biological Sciences, University of Surrey, Guildford, UK.
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MeSH Terms
Alkane 1-Monooxygenase
Cell Division / drug effects
Cytochrome P-450 CYP1A2
Cytochrome P-450 Enzyme System / biosynthesis*
Enzyme Induction / drug effects
Liver / drug effects*,  metabolism
Microbodies / drug effects*
Mixed Function Oxygenases / biosynthesis*
Oxidoreductases / biosynthesis*
Plant Extracts / pharmacology
Rats, Wistar
Reg. No./Substance:
0/Plant Extracts; 0/Tea; 9035-51-2/Cytochrome P-450 Enzyme System; EC 1.-/Mixed Function Oxygenases; EC 1.-/Oxidoreductases; EC P-450 CYP1A2; EC 1-Monooxygenase

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