Radiosensitivity and dose fractionation effects in culture cells

Survival, division delay and repair of sublethal damage were studied as a function of the cellular age in cells of EUE line exposed to 31 MeV protons, (LET of 1.83 keV/μm in tissue). The findings are compared with data reported in the literature on various mammalian cell lines exposed to X and γ rays, common behaviours are pointed out and the characteristic parameters quantified. Survival varyes with cell age and reaches a maximum value at mid S and its minimum at late G1; the ratio between maximum and minimum ranges between 1.5 and 15 depending on the survival level. Division delay resulted to be equal to 6 and 12% of the generation time per Gy for mid G1 and mid-late S respectively. All the investigated lines are able to repair as much as 50% of the sublethal damage within one hour