Reduction of radiation sensitivity of microorganisms using a scavenger of OH radicals at different dosage rates of gamma rays

The aim of this work was to study the dependence of the reduction rate of the radiation sensitivity of the yeast Saccharomyces cerevisiae by uptake of hydroxyl radicals at the dose rate of gamma radiation. Methanol or ethanol were used as a scavenger of OH radicals. Irradiation was done by radionuclide ⁶⁰Co placed in a commercial source Gammacell 220. Dose rates were 18; 28; 35 and 42 Gy/hr. The degree of radiation sensitivity was defined as the slope of the proportion of the natural logarithms of fractions of surviving cells without scavenger and with scavenger on the trapping efficiency of the scavengers. It was found that the progression of variable dependency on the dose rate is similar for both studied scavenger (monotonic increase of radiation sensitivity of tumour cells with increasing dose rate up to about 40 Gy/h), which is likely to be related with their similar nature (simple alcohols). Reference experiments suggest that both alcohols may have nonlinear dependence with a maximum at dose rate greater than the above-mentioned value. (Authors)