Reduction of diepoxybutane-induced sister chromatid exchanges by glutathione peroxidase and erythrocytes in transgenic Big Blue (R) mouse and rat fibroblasts

We have investigated the effect of glutathione peroxidase (GSH-Px) and mamm alian erythrocytes (RBCs) on spontaneous and diepoxybutane (DEB)-induced si ster chromatid exchange (SCE) in primary Big Blue(R) mouse (BBM1) and Big B lue(R) rat (BBR1) fibroblasts. DEB is the putative carcinogenic metabolite of 1,3-butadiene (BD) for which inhalation exposure yields a high rate of m alignancies in mice but not in rats. ED is metabolized differently in mice and rats, producing much higher levels of DEB in mice than in rats, which m ay partly explain the different carcinogenic responses. However, other fact ors may contribute to the observed differences in the rodent carcinogenic r esponse to ED. DEB is a highly reactive compound. Upon epoxide hydrolysis, DEB can covalently bind to DNA bases. Likewise, DEB generates reactive oxyg en species that, in turn, can either damage DNA or produce H2O2. Reduced gl utathione (GSH) is known to play a role in the metabolism and detoxificatio n of DEB; and GSH is reduced by GSH-Px in the presence of H2O2. GSH-Px is a constitutive enzyme that is found at high concentrations in mammalian RBCs . Therefore, we were interested in examining the role of RBCs and GSH-Px on DEB-induced SCE in rat and mouse cells for detection of possible differenc es in the species response. Transgenic BBM1 and BBR1 fibroblasts were treat ed with either 0, 2 or 4 mu M DEB plus 0, 2 or 20 units of GSH-Px with and without 2 x 10(8) species-specific RBCs. DEB effectively induced SCEs in bo th rat and mouse cells. The relative induction of SCEs in both cell types w as comparable. Both GSH-Px and RBCs alone and in combination were effective in significantly reducing DEB-induced SCEs in both mouse and rat fibroblas ts, although there was more variability in the SCE response in rat cells. T he present study suggests that GSH-Px may be important in the detoxificatio n of DEB-induced DNA damage that results in the formation of SCEs. (C) 2000 Elsevier Science B.V. All rights reserved.