To assess the genetic control of the induction of the adaptive response after low-dose ionizing radiation, the frequencies of chromosome aberrations were evaluated in four pairs of monozygotic twins, two pairs of dizygotic twins, and in nine unrelated individuals. Stimulated cells were exposed to adaptive dose of 5 cGy gamma rays at 24 h and challenge dose of 150 cGy gamma rays at 42 h. Cells were fixed at 48 h and chromatid and isochromatid breaks were evaluated. The adaptive response was found in two pairs of monozygotic twins, but not in the two other pairs. Individual differences in adaptive response between the members of monozygotic twins were very small. In contrast, the variability in the adaptive response between the members of dizygotic twins was much greater and was similar to that observed in the unrelated donors. The results confirmed that heterogeneity in the adaptive response after exposure to low-dose gamma rays was controlled genetically to a considerable extent.

Department of Medical Biology School of Medicine Safarik University Kosice Slovak Republic