[Relationship between dose rate and oxygen effect (author's transl)]

Chinese hamster cells were exposed to 60Co gamma-rays using dose rates between 3.64 and 0,01 Gy/min under euoxic or chronically hypoxic conditions of growth in order to clarify the relationship of the oxygen enhancement ratio (OER) to the dose rate. It turned out that the D0 of dose-effect curves from cells irradiated under euoxic conditions was increasing from 1.35 to 4.5 Gy with decreasing dose rates, whereas the curves from cells irradiated under chronically hypoxic conditions were not much influenced by the dose rate. The oxygen enhancement ratio decreased from 3.9 with 1.35 Gy/min to 1.8 with 0.07 Gy/min.