Radiation-induced DNA damage and cellular lethality in cultured mammalian cells.

X ray-induced DNA scissions and their repair were studied by an alkaline separation method. DNA damage in Chinese hamster V79 cells was assigned to one of three groups based on a repair profile previously used for mouse L5178Y cells: fast-reparable (T1/2 = 5 min), slow-reparable (T1/2 = 70 min), and nonreparable . The three kinds damage were investigated in relation to cellular lethality under conditions where radiosensitivity of cultured cells was modified: (1) different sensitivity in different cell lines, (2) cell cycle fluctuation of radiosensitivity, and (3) recovery after split-dose irradiation. Among the three types of lesions, only nonreparable damage or remaining lesions showed correlation to cell killing. The parallel relationship between nonreparable damage and cell killing implies that this type of damage could play an important role in radiation-induced cell death.