X-irradiation of Mitotic Chinese Hamster Cells

Abstract

Chinese hamster ovary (CHO) cells synchronized in mitosis are more sensitive to X-ray-induced cell killing than cells in the G₁, early S or late S phases of the cell-cycle. In addition, radiation damage registered in mitotic cells is expressed by surviving daughter cells during the G₁ and S phase as a reduced capacity to accumulate additional sublethal radiation damage. The magnitude of the reduction in the survival curve shoulder is dependent on the radiation dose administered to the cells in mitosis. During the interval from late S of the first generation after mitotic irradiation to G₁ of the second generation, surviving cells recover the full capacity to accumulate sublethal damage. Thus, mitotic cells sustain at least two types of radiation damage: (1) lethal, irreparable damage, and (2) sublethal damage, i.e. fully reparable, but which can contribute to lethality if additional radiation is delivered before complete recovery.