title: Effects of green and black tea biocomposites on endogenous synthesis, metabolism and genotoxic effect of carcinogenic N-nitrosodimethylamine.
abstract: OBJECTIVE
  To study the modifying effect of green and black tea biocomposites on endogenous synthesis and genotoxic action of the carcinogenic N-nitrosodimethylamine.
  
  
  METHODS
  Green and black tea biocomposites were administered to the white inbred rats in vivo. Amidopyrine and sodium nitrite were used as N-nitrosodimethylamine precursors and 4-methylpyrazol as an inhibitor of its metabolism. N-nitrosodimethylamine (blood, daily urine and reaction mixture), nitrites and nitrates (daily urine) levels were measured. Genotoxic action was tested by formation of DNA single-strand breaks in hepatocytes.
  
  
  RESULTS
  In in vitro system, biocomposites increased N-nitrosodimethylamine synthesis in neutral medium and decreased in acid conditions. In vivo, black tea biocomposite consumption resulted in enhanced background level of DNA single-strand breaks in rats hepatocytes and higher genotoxic effect upon administration of N-nitrosodimethylamine precursors. The levels of N-nitrosodimethylamine in blood and urine of experimental animals were increased after precursors' administration. In contrast, green tea biocomposite significantly decreased background level of DNA single-strand breaks. However, there was no protective action of this food supplement at the N-nitrosodimethylamine, precursors' administration. 4-methylpyrazol administration did not increase N-nitrosodimethylamine excretion in urine, while this effect was observed in control and black tea biocomposite groups.
  
  
  CONCLUSIONS
  The effects of green tea and black tea biocomposites on N-nitrosodimethylamine synthesis in in vitro system are unidirectional and depend on biocomposites' concentration and acidity of the medium. Long-term consumption of black tea biocomposite resulted in intensification of endogenous N-nitrosodimethylamine synthesis and increased damage of the hepatocytes' DNA. As to the green tea biocomposite, the obtained results allow us to suggest that this biocomposite enhanced N-nitrosodimethylamine metabolism.
authors.affiliation: R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology NAS of Ukraine, Kiev 03022, Ukraine. veterok61@mail.ru
authors.forename: O A
authors.initials: OA
authors.lastname: Glavin
authors.forename: P M
authors.initials: PM
authors.lastname: Mikhailenko
authors.forename: S P
authors.initials: SP
authors.lastname: Zaletok
authors.forename: L
authors.initials: L
authors.lastname: Gulua
mesh_terms: D000818:Animals; D028241:Camellia sinensis / Q000737:chemistry / Q000378:metabolism; D002273:Carcinogens / Q000378:metabolism* / Q000633:toxicity; D053904:DNA Breaks, Single-Stranded / Q000187:drug effects*; D004128:Dimethylnitrosamine / Q000378:metabolism* / Q000633:toxicity; D008297:Male; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D013662:Tea / Q000737:chemistry / Q000378:metabolism
chemical_list: D002273:Carcinogens; D010936:Plant Extracts; D013662:Tea; D004128:Dimethylnitrosamine