Chromosomal instability in in vivo radiation exposed subjects

To investigate whether delayed chromosomal instability arises in human peripheral T lymphocytes exposed in vivo to gamma-irradiation.

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 exposure and one apparently unexposed person were studied. Two Estonian controls 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-term cultures established from whole blood.

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 cultures established at different time intervals after the exposure). However, when the lymphocytes were cultured long term in vitro, chromosomal instability was observed. There was no dose-response, and the appearance of chromosomally unstable cells in long-term cultures was also observed in a subject exposed to a dose of less than 0.1 Gy. Moreover, in contrast with previous findings, 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.

Chromosomal instability was observed in long-term cultures of donors with in vivo exposure to gamma-radiation. No dose-response was apparent. However, in contrast with previous findings, signs of chromosomal instability 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.