title: Effect of hyperthermia on DNA single-strand breaks induced by bleomycin in Hela cells.
abstract: The effect of hyperthermia (43 approximately 45 degrees) on DNA single-strand breaks induced by bleomycin was examined in HeLa cells by the alkaline sucrose gradient sedimentation analysis. When HeLa cells were exposed to a temperature of 43 degrees approximately 45 degrees for 1 hr, only a small number of DNA single-strand breaks than bleomycin treatment at 37 degrees. The DNA strand breaks induced by bleomycin were almost completely repaired by post-treatment incubation of the cells in the control medium at 37 degrees. On the contrary, the repairing capacity of the cells was markedly inhibited by post-treatment incubation at 43 degrees, and this inhibition of cell repair seemed irreversible because no repair was found after an additional incubation of the cells at 37 degrees for 1 hr. These results support the possibility that the mechanism of synergism between the effect of bleomycin and hyperthermia may be related to the inhibition of DNA repair.
mesh_terms: D001761:Bleomycin / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004260:DNA Repair / Q000187:drug effects; D004277:DNA, Single-Stranded / Q000032:analysis*; D006367:HeLa Cells; D006358:Hot Temperature; D006801:Humans
chemical_list: D004277:DNA, Single-Stranded; D001761:Bleomycin