The relationship between the RBE of alpha particles and the radiosensitivity of different mutations of Chinese hamster cells

The RBE of alpha -particles in different mutations of Chinese hamster cells was determined with the aim of identifying differences in the sensitivity to x-ray and alpha -particle-induced DNA damage. Two parental lines of Chin ese hamster cells and four radiosensitive mutants were irradiated with diff erent single doses of x-rays and alpha -particles and clonogenic cell survi val was determined. Radiosensitivity to x-rays varied by a factor of 5 betw een the cell strains whereas sensitivity to alpha -particle irradiation was almost identical among all strains. The RBE is only determined by the sens itivity of the cells towards x-rays. Since cells with different defects of repair or cell cycle control have different radiosensitivities, we conclude that the effects of x-ray irradiation and the RBE are mostly determined by the activity of repair processes.