[Effect on cell genotype on thermal radiosensitization of yeast]

The combined action of hyperthermia and ionizing radiation on the arrival of isogenic haploid and diploid yeast cells of wild type and rad51 mutant was studied. The experiments demonstrated the essential enhancement of radiosensitivity of diploid wild type cells is hyperthermic conditions. For haploid wild type cells and rad51 mutant cells the enhancement was smaller and negligible respectively. The action of both factors on rad51 homozygous diploid cells was additive. It is established that diploid cells were less thermosensitive than haploid ones. Rad51 mutation does not change these properties. It was concluded that the enhancement of radiosensitivity of cells under hyperthermic conditions depends on cell genotype and may be caused by the reduced capacity of cells to recover the radiation damages inflicted by the both modalities.