Bleomycin induces similar survival variations through the cell cycle as do X rays with and without hypertonic shock

In an earlier report [H. Utsumi and M. M. Elkind, Radiat. Res. 119, 534-541 (1989)], it was shown that the survival of V79 Chinese hamster cells treated with bleomycin was significantly reduced by a posttreatment with anisotonic phosphate-buffered saline in a manner that was qualitatively similar to what had been observed with X rays [H. Utsumi and M. M. Elkind, Radiat. Res. 77, 346-360 (1979)]. This similarity suggested that similarities might exist in the cyclic variation in the suppression of the repair of potentially lethal damage following treatment with bleomycin or X rays. Accordingly, the age-response variations of survival, with or without a posttreatment challenge with hypertonic buffer, were compared in the same experiment when cells were treated with either agent. Although a significant difference was observed near the G1/S-phase border, in general the damage induced by the two agents showed a similar dependence on cell age, and posttreatment with hypertonic buffer enhanced cell killing appreciably following either treatment. The results support the inference that bleomycin is a radiomimetic agent.