Heavy Ion-induced Chromosome Breakage Studied by Premature Chromosome Condensation (PCC) in Syrian Hamster Embryo Cells

Abstract

We have studied induction and repair of chromosome damage induced by high linear energy transfer (LET) heavy ions in G₁/G₀ interphase Syrian golden hamster embryo (SHE) cells as revealed by the premature chromosome condensation (PCC) technique. The number of chromosome breaks in condensed chromosomes induced by high LET heavy ions was higher than those induced by ¹³⁷Cs gamma-rays. Compared with ¹³⁷Cs gamma rays, the relative biological effectiveness (RBE) for PCC breaks was 1·5 for 35 keV/µm ⁴He ions, 1·9 for 77 keV/µm ⁴He ions, and 2·5 for 530 keV/µm ¹⁴N ions. Although 95% of the PCC breaks induced by gamma-rays rejoined during 8 h post-irradiation incubation, only 35–45% of fragments induced by high LET radiations rejoined in the same time. These results suggest that there is a difference, spatial or qualitative, in the initial chromosome damage produced by high LET radiations and low LET radiations.