DETECTION OF HEAVY-ION-INDUCED DNA DOUBLE-STRAND BREAKS USING STATIC-FIELD GEL-ELECTROPHORESIS

Radiation-induced DNA double-strand breaks (DSBs) were measured in Chi nese hamster ovary cells (CHO-K1) using an experimental protocol invol ving static-field gel electrophoresis following exposure to various ac celerated ions. Dose-effect curves were set up, and relative biologica l efficiencies (RBEs) for DSB induction were determined for different radiation qualities. RBEs around 1 were obtained for low energy deuter ons (6-7 keV/mu m), while for high energy oxygen ions (20 keV/mu m) an RBE value slightly greater than 1 was determined. Low energetic oxyge n ions (LET approximate to 250 keV/mu m) were found to show RBEs subst antially below unity, and for higher LET particles (greater than or eq ual to 250 keV/mu m) RBEs for DSB induction were generally found to be smaller than 1. The data presented here are in line with the generall y accepted view that not induced DSBs, but rather misrepaired or unrep aired DNA lesions are related to cellular inactivation.