Analysis of chromatid damage in G2 phase induced by heavy ions and X-rays

The induction of chromatid aberrations was examined in Golden hamster embryo (GHE) cells 2 h after exposure to X-rays or heavy ions. Compared with X-rays the frequencies of gaps and deletions were almost one-half in the case of He ions, and much lower in cells irradiated with N ions. The induction of exchanges by He ions and N ions was also less than that by X-rays. The relative number of gaps, deletions and exchanges were 0.4, 0.5 and 0.4 for He ions, and 0.2, 0.2 and 0.4 for N ions. The mitotic indices were almost the same in X-irradiated and heavy-ion-exposed cells. Chromatid aberrations induced by heavy ions tended to persist longer than those induced by X-rays during successive culture passages after exposure. The present results suggest a difference in the quality of chromatid damage induced by X-rays and heavy ions.