ENVIRONMENTAL RADIATION DOES NOT ENHANCE THE TOLERANCE OF YEAST CELLS TO ACUTE RADIATION EXPOSURE

摘要

The aim of the investigations was to clarify whether cells adapted to the normal background radiation show enhanced resistance to the damaging effects of ionizing radiation. The underground laboratory for dosimetry and spectrometry (UDO) of the Physi-kalisch-Technische Bundesanstalt (PTB) at a depth of 925 m allowed to grow cells at a dose rate of 2.2 nSv/h compared with about 110 nSv/h of the normal background radiation. The yeast mutant rad54-3 which is temperature conditional for the repair of DNA double-strand breaks (dsb) was cultivated at 2.2 and 110 nSv/h, respectively, and irradiated in UDO using electrons (~(90)Sr/~(90)Y). This mutant rad54-3 allows to determine separately induction and repair of dsb, solely by cultivating irradiated cells at 36 °C (no dsb repair) or at 23 °C (with dsb repair). The results show that the normal background radiation does not adapt yeast cells for reduced initial dsb and elevated repair of dsb.