Detection of heavy-ion-induced DNA double-strand breaks using static-field gel electrophoresis.

Radiation-induced DNA double-strand breaks (DSBs) were measured in Chinese hamster ovary cells (CHO-K1) using an experimental protocol involving static-field gel electrophoresis following exposure to various accelerated ions. Dose-effect curves were set up, and relative biological efficiencies (RBEs) for DSB induction were determined for different radiation qualities. RBEs around 1 were obtained for low energy deuterons (6-7 keV/microns), while for high energy oxygen ions (20 keV/microns) an RBE value slightly greater than 1 was determined. Low energetic oxygen ions (LET approximately 250 keV/microns were found to show RBEs substantially below unity, and for higher LET particles (> or = 250 keV/microns) RBEs for DSB induction were generally found to be smaller than 1. The data presented here are in line with the generally accepted view that not induced DSBs, but rather misrepaired or unrepaired DNA lesions are related to cellular inactivation.