Chromosomal instability in in vivo radiation exposed subjects

Purpose: To investigate whether delayed chromosomal instability arises in h uman peripheral T lymphocytes exposed in vivo to gamma-irradiation. Materials and methods: Long-term cultures were established from lymphocytes obtained from subjects involved in the radiological accident in Estonia in 1994. Two individuals exposed to a high dose, one individual with low expo sure and one apparently unexposed person were studied. Two Estonian control s not involved with the accident were also analysed. Cells were grown for 6 -42 days and chromosomal aberrations were assessed from G-banded metaphases . In addition, FISH chromosome painting analysis was performed on short-ter m cultures established from whole blood. Results: No obvious sign of chromosomal instability was observed in the in vivo follow-up of the frequencies of chromosomal aberrations in lymphocytes of radiation accident victims performed by the FISH technique (48 h cultur es established at different time intervals after the exposure). However, wh en the lymphocytes were cultured long term in vitro, chromosomal instabilit y was observed. There was no dose-response, and the appearance of chromosom ally unstable cells in long-term cultures was also observed in a subject ex posed to a dose of less than 0.1 Gy. Moreover, in contrast with previous fi ndings, chromosomal instability was also observed in cells from non-exposed control individuals. The chromosomal changes observed in the controls were less complex than the aberrations in the cultures derived from individuals exposed to high doses. Conclusions: Chromosomal instability was observed in long-term cultures of donors with in vivo exposure to gamma-radiation. No dose-response was appar ent. However, in contrast with previous findings, signs of chromosomal inst ability were observed also in long-term cultures from non-exposed controls. Further studies are needed to assess possible inter-individual differences in the induction of chromosomal instability.