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DNA BINDING POTENTIAL OF BROMODICHLOROMETHANE MEDIATED BY GLUTATHIONE S-TRANSFERASE THETA 1-1
Citation:
Pegram, R A. AND M. K. Ross. DNA BINDING POTENTIAL OF BROMODICHLOROMETHANE MEDIATED BY GLUTATHIONE S-TRANSFERASE THETA 1-1. Presented at SOT, San Francisco, CA, March 25-29,2001.
Description:
DNA BINDING POTENTIAL OF BROMODICHLOROMETHANE MEDIATED BY GLUTATHIONE S-TRANSFERASE THETA 1-1. R A Pegram1 and M K Ross2. 2Curriculum in Toxicology, University of North Carolina, Chapel Hill, NC; 1Pharmacokinetics Branch, NHEERL, ORD, United States Environmental Protection Agency, Research Triangle Park, NC, USA.
Sponsor: H. Barton
The disinfection by-product bromodichloromethane (BDCM) has previously been shown to be mutagenic in a Salmonella typhimurium strain transformed with rat GST theta 1-1 (strain RSJ 100). Two experimental approaches have been undertaken to investigate the DNA binding potential of reactive intermediates generated by GST-mediated metabolism of BDCM: (1) in vitro rodent hepatic cytosol incubations containing [14C]-BDCM (5 mM), supplemented GSH, and calf thymus (ct) DNA; (2) treatment of the S. typhimurium strain RSJ 100 with increasing concentrations of [14C]-BDCM. In the first approach, ~ 3-fold (rat liver cytosol) and 7-fold (mouse liver cytosol) greater amounts of [14C]-BDCM-derived radioactivity were found associated with isolated ctDNA when compared with a control (absence of rodent cytosol) following liquid scintillation counting (LSC) of isolated DNA; however, further characterization of this DNA-associated radioactivity could not be assigned to a specific deoxynucleoside adduct(s) following hydroxyapatite chromatography and/or enzymatic hydrolysis of ctDNA. In the second approach, a concentration-dependent increase in S. typhimurium DNA-associated radioactivity was observed following LSC of isolated DNA, but further characterization was again unsuccessful following hydroxyapatite chromatography and/or enzymatic hydrolysis. One possibility to account for the above observations is the formation of a "transient" adduct that is unstable in the DNA isolation procedures employed. Additional experiments will include [35S]-GSH to facilitate identification of products derived from the GST-catalyzed pathway. (This abstract does not reflect EPA policy.)