Bleomycin and misonidazole cytotoxicity.

Chinese hamster ovary (CHO) cells were exposed in vitro to combinations of bleomycin and misonidazole under hypoxic conditions. Only one drug was present at any given time and cells were washed before being exposed to the second drug. Both drugs induced potentially lethal damage (PLD). This damage was repaired under hypoxic conditions very rapidly, and bleomycin-induced PLD was repaired more rapidly than misonidazole-induced PLD. If, after the combined treatment, cells are kept in hypoxia, much of the damage can be repaired.