Evidence for binding of metabolically activated 1,2-dibromoethane to chromatin of forestomach and liver.

The covalent binding of metabolically activated 1,2-dibromoethane (DBE), a potent carcinogen, to chromatin constituents of forestomach and liver was examined in vitro. Chromatin was prepared from forestomach and liver of B6C3F1 mice and characterized. In order to activate DBE, microsomes and cytosol were isolated from mouse forestomach and liver and incubated with [14C]-DBE in the presence of a NADPH regenerating system. Results demonstrate that DBE bound covalently to the same extent to protein of microsomes and chromatin isolated from forestomach and liver. On the contrary, DBE bound significantly more to chromatin DNA of forestomach or liver than it did to salmon sperm DNA. It appears from these results that the metabolically activated DBE is more reactive to homologous DNA than exogenous DNA. Fractionation of DBE-bound chromatin protein into histone and nonhistone proteins resulted in higher binding of DBE to nonhistone than to histone proteins isolated from forestomach and liver.