CHROMATID DAMAGE-INDUCED BY PU-238 ALPHA-PARTICLES IN G(2)-PHASE AND S-PHASE CHINESE-HAMSTER V79 CELLS

The comparative induction of chromatid aberrations by Pu-238 alpha-par ticles, or by 250 kVp X-rays was investigated in V79 Chinese hamster c ells. Metaphases were sampled at hourly intervals postirradiation up t o 8 h and BrdU/FPG staining methods were used to distinguish G(2), S a nd G(1) phase cells. Two experiments were performed. In the first, an alpha-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 alpha-particles to prod uce a similar overall frequency of interchanges, and allow comparative ratios to be derived for other aberration types. At these isoexchange doses, alpha-particles produce relatively less gaps and breaks, parti cularly in late G(2), and significantly more isochromatid deletions. A very high proportion of the isochromatid deletions were incomplete af ter alpha-particles compared with X-rays, but no difference in incompl eteness was found for interchanges. With X-rays, about 6% of interchan ges are complex intra-interchange forms. At similar exchange frequenci es this increases to 26.7% for alpha-irradiation, suggesting increased multiple lesion interaction. Differences in dose distribution between a-particles and X-rays are discussed and mitotic delay is examined af ter separation of the analysed cells into damaged and undamaged classe s.