A Comparative Study of Several Survival Responses of Mammalian Cells After UV and After X-Irradiation

Summary

Dose response curves were obtained from Chinese hamster cells irradiated in different growth stages and under different nutritional conditions with either X-ray or ultraviolet light. All X-ray survival curves were asymptotically exponential, while the shape of the UV-curves was bi-phasic. Survival of X-irradiated cells was much less influenced by cultural factors than survival of cells exposed to UV. Recovery of cells from potentially lethal damage had a T1/2 of 1–2 h after exposure to the ionizing irradiation, while it took considerably longer to recover 50% of the UV induced damage. Similarly “fixation” of X-ray damage was relatively rapid (T1/2 ⋍ 30 min) compared to “fixation” of UV damage (T1/2 ⋍ 3.5 h). Finally, exposure of cells to 43°C for 1 h immediately after X-irradiation resulted in synergistic cell killing and subsequent complete inhibition of recovery from potentially lethal damage. On the other hand similar heat treatment of UV-exposed cells resulted only in additive cell killing and did not inhibit recovery.