Characterization of the hepatic DNA damage caused by 1,2-dibromoethane using the alkaline elution technique

The damage to hepatic cell DNA caused by i.p. administration of 1,2-dibromoethane (EDB) was studied in male Swiss Webster mice. Three hours after treatment, hepatic nuclei were isolated and damage to DNA assessed by the alkaline elution technique. The method for isolation of the nuclei preserved the integrity of the DNA and in addition it was found that the purified nuclei could be frozen for at least 1 week with no detectable damage to the DNA. EDB administration (25-75 mg/kg) resulted in a dose-dependent increase in DNA single-strand breaks. More DNA single-strand breaks were detected when lysed nuclei were preincubated in the alkaline eluting solution prior to analysis. The presence of these alkali-labile sites suggests that the DNA strand breaks result, in part, from the lability of DNA sites alkylated by EDB. There was no evidence of EDB induced DNA-DNA cross-links or DNA-protein cross-links. The use of isolated hepatic nuclei as a sample for alkaline elution analysis may be a useful technique for studying the nature of DNA damage induced in vivo by carcinogens.