Ultraviolet Light and X-Ray Damage Interaction in Chinese Hamster Cells

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Abstract
The age-response variations in survival of V79 Chinese hamster lung cells, following the combined administration of a fixed dose of X-rays and a dose of UV radiation, show enhanced cell killing at all cell ages. The greatest interaction is observed in the middle of the DNA synthetic phase where the shoulders on both the X-ray and UV survival curves are large. In the middle of the DNA synthetic phase, a dose of UV radiation reduces the ability of surviving cells to accumulate sublethal damage due to X-rays and vice versa; the amount of shoulder removed, however, is always greater when UV precedes X-rays. At equal survival levels, X-ray damage is completely additive to UV-induced sublethal damage, while UV damage is only in part additive to X-ray induced sublethal damage. If an interval for repair is introduced between these 2 types of radiation, the loss of interaction following a dose of X-rays is more rapid than following a dose of UV as judged by the rate of reappearance of the shoulder on the respective survival curves. The damage due to nonionizing and ionizing radiation in Chinese hamster cells interacts and is additive; this is because of overlapping action at the level of nuclear DNA.