The effects of Chinese tea on the methylation of DNA by the esophageal carcinogen N-nitrosomethylbenzylamine.
In order to investigate the mechanisms of the anticarcinogenic effect of Chinese tea on the development of esophageal tumors in rats induced by N-nitrosomethylbenzylamine, the alkylation of DNA in various organs was studied in rats treated with 2 varieties of Chinese tea, i.e. Fujian Oolong tea and Jasmine tea. Male Wistar rats were given a single i.v. injection of N-nitroso-[methyl-14C]-benzylamine (2.5 mg/kg body wt) after having been provided tea in drinking water and by gavage for 2-3 weeks. Control rats were provided with tap water. Three to four hours after administration of the N-nitroso compound, the methylation of purine bases in the DNA isolated from various organs was measured by high performance liquid chromatography and liquid scintillation counting. In the tea-drinking rats, there was an appreciable reduction of O6-methylguanine formation in the esophageal DNA as well as the ratio of O6-methylguanine to N7-methylguanine, as compared to the control rats. No O6-methylguanine was detected in lung or liver DNA.
Zhu
J Q
JQ
Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine, Beijing.
Xiao
Y
Y
Liu
Z Q
ZQ
Chen
J S
JS
Guo
Z L
ZL
D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D001345:Autoradiography; D004247:DNA / Q000378:metabolism*; D004128:Dimethylnitrosamine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors; D004938:Esophageal Neoplasms / Q000139:chemically induced / Q000517:prevention & control*; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D008297:Male; D008745:Methylation; D011685:Purine Nucleotides / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D013662:Tea
D016588:Anticarcinogenic Agents; D011685:Purine Nucleotides; D013662:Tea; D006147:Guanine; D004247:DNA; C014707:nitrosobenzylmethylamine; C008449:O-(6)-methylguanine; D004128:Dimethylnitrosamine