These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: The relationship between N-nitrosodimethylamine metabolism and DNA methylation in isolated rat hepatocytes.
    Author: Encell L, Foiles PG, Gold B.
    Journal: Carcinogenesis; 1996 May; 17(5):1127-34. PubMed ID: 8640923.
    Abstract:
    The metabolism of N-nitrosodimethylamine (NDMA) and its methylation of DNA were simultaneously determined in hepatocytes isolated from untreated and saline- and pyrazole-treated male Sprague-Dawley rats. Metabolism of NDMA was directly measured by monitoring its disappearance via gas chromatography coupled with a sensitive and specific detector for N-nitrosamines. DNA methylation was determined in the same cells employed in the metabolism studies using a monoclonal antibody-based competitive ELISA procedure specific for O6-methyldeoxyguanosine (6-Me-dG). The apparent Km and Vmax for NDMA metabolism are 61 microM and 56 pmol/min/10(6) cells respectively for hepatocytes isolated from untreated rats. It was found that the addition of pyrazole to the in vitro hepatocyte incubations caused a dose-dependent inhibition of both metabolism and DNA methylation. However, when DNA methylation is expressed as a function of NDMA metabolized, there is no significant difference between hepatocyte incubations without or with pyrazole, with an average value of 79 nmol 6-Me-dG/mol dG/nmol NDMA metabolized. Based on the pyrazole inhibition studies, cytochrome P450IIE1 is responsible for at least 60% of the DNA methylation in rat hepatocytes. In pyrazole-pretreated rats there was an inconsistent increase in NDMA metabolism, but when metabolism was elevated so was DNA methylation. In contrast, microsomes isolated from pyrazole-pretreated rats consistently showed elevated metabolism of NDMA. Based on the simultaneous determination of adduct levels and metabolism, there is approximately 1 6-Me-dG adduct formed/133 000 NDMA molecules metabolized in the uninduced hepatocytes.
    [Abstract] [Full Text] [Related] [New Search]