PROPYLENE-OXIDE AND EPICHLOROHYDRIN INDUCE DNA STRAND BREAKS IN HUMAN-DIPLOID FIBROBLASTS

The induction of DNA strand breaks in human diploid Fibroblasts (VH-10 ) was demonstrated after in vitro exposure with two carcinogenic epoxi des, propylene oxide (PO) and epichlorohydrin (ECH). Alkaline DNA unwi nding (ADU), pulsed field gel electrophoresis (PFGE), and the comet as say were used to measure DNA single- (SSBs) and double-strand breaks ( DSBs). A dose-dependent increase of DNA strand breaks, measured by ADU , was observed in the dose range 2.5-20 mMh of PO and 0.25-2 mMh of EC H. The dose-response of ECH was about five times higher compared with that of PO (211 vs. 41 SSBs.100 Mbp(-1).mMh(-1)). The induction ra:es of DSBs, measured by PFGE, were found to be 18 times higher for ECH co mpared to PO (4.8 and 0.27 DSBs.100 Mbp(-1).mMh(-1) for ECH and PO, re spectively). Using these two methods, the SSBs/ DSBs ratio was estimat ed to be 148 for PO and 44 for ECH. The data obtained by the comet ass ay also demonstrated a dose-dependent ability of PO and ECH to induce DNA damage. it was found that ECH was about six times more effective a s an inducer of DNA strand breaks compared to PO (200 and 32.100 Mbp(- 1).mMh(-1) for ECH and PO, respectively). The SSBs/DSBs ratios calcula ted using comet assay and PFGE data were 125 For ECH and 41 For PO. In addition, ECH is about 10 times more toxic than PO with respect to su rvival. These properties of ECH can at least in part be explained by i ts higher chemical reactivity connected with a higher rate of DNA alky lation. (C) 1997 Wiley-Liss, Inc.