The Influence of Ionization Density on the DNA Synthetic Phase and Survival of Irradiated Mammalian Cells

Abstract

Depression of the DNA synthetic rate of exponentially growing V79 cells [chinese hamster lung cells] was transient with a dose-dependent maximum at 1 h after exposure to sparsely or densely ionizing radiation. The dose-effect curves were biphasic for 241Am .alpha.-particles as well as for 60Co .gamma.-rays, being partly congruent if inhibition of DNA synthesis was expressed per S-phase cell. The lesions responsible caused a prolongation of the DNA synthetic period (S-phase) after sparsely ionizing X- or 60Co .gamma.-rays. No such effect was observed during the first 4 h after exposure to densely ionizing alpha particles, peak pions and high LET [linear energy transfer] neon ions. The effect was dose-rate independent. The inhibition of the DNA synthetic rate seems to be only partly related to survival.