Plateau-phase human dermal fibroblasts and whole blood G0 lymphocytes obtained from the same three healthy donors were irradiated with different doses of 200 kV X rays. The genomic yields of dicentrics were evaluated in the first postirradiation mitosis. Fluorescence in situ hybridization was used to "paint" the chosen whole chromosomes. The yields of reciprocal translocations were scored for all donors for chromosome 4, and also for the third donor for chromosomes 7 and 9. The amounts of reciprocal translocations were scored in the first as well as in later (4th or 5th) postirradiation cell divisions. The yields of dicentrics involving the painted chromosomes were scored for one donor as well. The yields of dicentrics observed in the lymphocytes and in the skin fibroblasts from the same individual were significantly different. Yields of dicentrics were much lower in fibroblasts than in lymphocytes. This was observed for all doses up to 4 Gy for all three donors studied. Fibroblasts from two individuals were also irradiated with 6 Gy. The interindividual variability was similar in both cell types. The yields of reciprocal translocations in lymphocytes and in fibroblasts were similar. The yields of reciprocal translocations were practically constant when comparing the first mitotic divisions and later divisions. The observed ratio of translocations:dicentrics was higher in fibroblasts than in lymphocytes, where it was about 1 for one donor and about 2 for the other two donors. Significant differences between the yields of dicentrics and translocations as well as between the shapes of their dose responses were observed in lymphocytes and fibroblasts from the same individual. Our experimental data suggest that repair processes with different or different repair processes might be active in cells of different types of tissue.

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