Chromatid Damage Induced by ²³⁸Pu α-particles in G₂ and S Phase Chinese Hamster V79 Cells

Abstract

The comparative induction of chromatid aberrations by ²³⁸Pu α-particles, or by 250 kVp X-rays was investigated in V79 Chinese hamster cells. Metaphases were sampled at hourly intervals postirradiation up to 8h and BrdU/FPG staining methods were used to distinguish G₂, S and G₁ phase cells. Two experiments were performed. In the first, an α-particle dose of 0·41 Gy was compared with an X-ray dose of 1·5 Gy used in a previously published study. In the second, an X-ray dose of 1·2 Gy was used in parallel with 0·41 Gy of α-particles to produce a similar overall frequency of interchanges, and allow comparative ratios to be derived for other aberration types. At these isoexchange doses, α-particles produce relatively less gaps and breaks, particularly in late G₂, and significantly more isochromatid deletions. A very high proportion of the isochromatid deletions were incomplete after α-particles compared with X-rays, but no difference in incompleteness was found for interchanges. With X-rays, about 6% of interchanges are complex intra-interchange forms. At similar exchange frequencies this increases to 26·7% for α-irradiation, suggesting increased multiple lesion interaction. Differences in dose distribution between α-particles and X-rays are discussed and mitotic delay is examined after separation of the analysed cells into damaged and undamaged classes.