Influence of the dose rate of gamma irradiation and some other conditions on the radiation protection of microbial cells by scavenging of OH radicals

Study of cell protective effects of alcohols against UV-C radiation and comparison to gamma radiation

A singlet oxygen production was monitored using a singlet oxygen sensor green chemical probe; reaction of chemical probe with singlet oxygen produces a fluorescent endoperoxide. Adding ethanol to the irradiated system resulted in decrease of the fluorescence signal, which indicates a decrease in concentration of singlet oxygen formed under UV-C irradiation. Thus, ethanol was likely to quench singlet oxygen in a system under study. This quenching did not occur with the use of methanol. When irradiating E. coli cells in the presence of ethanol and Rose Bengal for higher singlet oxygen production, there was a greater reduction in the radiation sensitivity of the cells compared to the system without Rose Bengal. Higher concentration of ethanol caused greater protection of cells; thus, it is likely that ethanol can scavenge singlet oxygen and provide a partial protection of bacteria from the effects of UV-C radiation. These results were compared with previously published data where the bacteria were irradiated by gamma radiation in presence of alcohols.

RADIOPROTECTIVE EFFECT OF HYDROXYL RADICAL SCAVENGERS ON PROKARYOTIC AND EUKARYOTIC CELLS UNDER VARIOUS GAMMA IRRADIATION CONDITIONS

The influence of various hydroxyl radical scavengers such as methanol, ethanol and dimethyl sulfoxide on radiation sensitivity of prokaryotic cells (bacteria Escherichia coli) and eukaryotic cells (yeast Saccharomyces cerevisiae and V79 cells-Chinese hamster pulmonary fibroblasts) irradiated by 60Co gamma radiation was investigated. The dependence of radiation sensitivity on dose rate in range from 1.8 to 100 Gy h-1 was evaluated. Survival of cells irradiated by increasing dose rates was followed using clonogenic assay. Specific protective effect was found to be a nonmonotonous function of dose rate with typical maximum at the dose rate range from 50 to 55 Gy h-1 in all studied cell types.