Bleomycin-induced potentially lethal damage and its repair.

The dependence of the survival of V79 Chinese hamster cells which were treated with bleomycin on a post-treatment with anisotonic phosphate-buffered saline and/or conditioned medium was examined. In qualitative similarity to the effects of these post-treatments on survival following exposure to X rays, it was found that: anisotonic saline, both hypo- and hypertonic, significantly enhanced cell killing; the degree of enhancement increased with time and temperature; and incubation in conditioned medium resulted in the rescue of cells whether or not they were challenged with hypertonic saline after treatment with bleomycin. Based upon the qualitative similarity of these findings to those which we have observed following X irradiation, and observations of others on the site of action of bleomycin in cells and the ability that it has to break DNA, we propose that both bleomycin and radiation (X rays and fast neutrons) act on similar sensitive sites which are probably contained in or close to the envelope and/or the protein matrix of the nucleus.