Some factors affecting the sensitivity of cultured human cells to high-LET radiation.

Comparative effects of decay of DNA-bound 125I, of gamma-radiation and of tritiated water on survival of the proliferative ability of cultured cells were examined. The results confirm a previous report that cells frozen to -196 degrees C in the presence of 2M glycerol have lost a considerable proportion of their intracellular water. The data also suggest that the fraction of the lethal damage caused by deposition of radiation energy in intracellular water close to the DNA is greater for gamma-radiation than for the decay of DNA-bound 125I. Inherited differences in the sensitivity of untransformed fibroblasts from individual humans to ionizing radiations and other DNA-damaging agents are being explored. The ratios of the sensitivities of various cell lines to particular agents can vary several-fold. Thus the RBE of various radiations is affected not only by the irradiation conditions and the water content of the cells but also by inherited abnormalities in the DNA repair systems in human cells.