Chromosome aberrations in human lymphocytes analysed by fluorescence in situ hybridization after in vitro irradiation, and in radiation workers, 11 years after an accidental radiation exposure.

Fluorescence in situ hybridization of metaphase chromosomes was used to determine the yield of symmetric and asymmetric exchange aberrations after in vitro exposure of peripheral lymphocytes to 250 kV X-rays (0-3.0 Gy). For the aberration analyses, chromosomes 2, 4 and 8 and all centromeres were painted. Centric rings amounted to about 8% of the dicentric yield. The proportion of inversions and insertions was about 5% of the total translocations. Regarding the spontaneous levels, the frequency of total induced translocations was higher by a factor of 1.13 than that of dicentrics. The involvement of chromosomes 2, 4 and 8 in translocations is significantly different from the expected ratio concerning physical length (p < 0.01). Furthermore, the frequency of translocations was evaluated in three radiation workers who received an accidental radiation exposure 11 years ago. About 75% of the translocations were identified as complete in comparison with 79% in the in vitro experiments. In the radiation workers chromosome 2 again showed an under-representation in translocations, whereas chromosome 4 was over-represented as in the in vitro experiments. The summarized results for the radiation workers showed a mean genomic translocation frequency of 13.4 per 1000 cells. This frequency is not significantly different from the mean frequency of dicentrics which were determined by conventional FPG staining, after detection of the accidental radiation exposure about 11 years ago (8.6 dic/1000 cells). There were, however, some differences between individuals affecting this comparison. The distribution patterns of dicentrics showed an over-dispersion, whereas the translocations occurred single in cells.