The effects in mice of combined treatments to X-rays and antineoplastic drugs in the Comet assay.

The Comet assay is a rapid, easy and reproducible method to detect genotoxic activity of chemical and physical agents in vitro and in vivo. In the present study the effects of exposure to irradiation or chemicals: cyclophosphamide (CP) and mitomycin C (MMC) or combined exposure to low doses of both agents (0.25 Gy+3.15 mg/kgbw CP and 0.25 Gy+0.25 mg/kgbw MMC) were examined for the induction of DNA damage in the Comet assay measured simultaneously in somatic (bone marrow lymphocytes) and haploid germ cells. The male mice were treated in vivo and sacrificed at 24 h after exposure. The percentage contents of DNA in the "comet tail" increased with increasing doses of X-rays and chemicals. After combined exposure to X-rays and CP and to X-rays and MMC weak increases of DNA damage in bone marrow lymphocytes and in germ cells were observed by comparison with the results obtained for each agent acting alone. There were slightly different responses in bone marrow lymphocytes and in germ cells, but effects were observed over a similar dose range.