DNA damage induced by gamma-radiation in combination with ethylene oxide or propylene oxide in human fibroblasts

To estimate the effects of interaction of gamma-rays and an epoxide, cell s urvival and induction of DNA double-strand breaks (DSBs) following combined exposure to ionizing radiation and ethylene oxide (EtO) or propylene oxide (PO) were studied in human fibroblasts. Two treatment protocols were appli ed: (a) the cells were pre-exposed to different doses of gamma-rays and the n treated with epoxide, and (b) the cells were pretreated with epoxide and then exposed to different doses of gamma-rays. Here we show that order of t he treatment did not play a role in cell survival and that the effect of co mbined exposure on cell killing was additive for both epoxides. As to DNA D SBs induction, however, a difference dependent upon the order of the treatm ent was observed. While EtO or PO treatment followed by gamma-rays exposure led to an increased number of DSBs at higher gamma-ray doses (2-3 Gy), no significant increase of DSBs was detected after the opposite order of the t reatment (gamma-ray exposure followed by EtO or PO treatment). (C) 2001 Els evier Science Ireland Ltd. All rights reserved.