Effects of hyperthermia and drug in cultured mammalian cells.

Hyperthermia (42 degrees C) and peptichemio (PTC) applied simultaneously result in an increased killing effect and in a significant induction of single strand breaks (SSB) of DNA molecule. The enhanced killing effect was observed in all circumstances, whenever hyperthermia was applied before, during or after PTC treatment, but the most effective cell killing was obtained when hyperthermia and PTC were applied simultaneously. The results show that PTC concentrations used in these experiments do not induce SSB in DNA molecule during incubation for 2 hours at 37 degrees C. When the cells were exposed to PTC and hyperthermia the induction of SSB was observed. The number of SSB depends on the exposure time and PTC concentration. Cells with a greater number of SSB lost the capacity for repair during post-incubation at 42 degrees C.