Abstract
It is well known that radiation-induced chromosomal translocation retains for a long time in hematopoietic cells in a dose-dependent manner. However, it is not yet clarified whether or not translocations retain for a long time after chronic low dose-rate radiation exposure. In the present study, we examined translocation rates in spleen cells from mice continuously exposed to low dose-rate gamma-rays. SPF C3H/HeN mice were continuously exposed from 8 weeks to 20 mGy/22 hr/day for a maximum of about 400 days. When the total accumulated doses reached 0.5, 1, 2, 4, and 8 Gy, spleen cells from mice were cultured for 48 hrs with LPS, Con A, and 2-ME for chromosome analysis. Chromosome aberrations of exchange type such as translocations were analyzed using multiplex-fluorescence in situ hybridization (M-FISH). Translocation rates did not increase until 456 days of age in non-exposed mice. In the irradiated mice, however, translocation rates increased depending on the total dose and were significantly higher than those of the age matched controls. These results showed that translocations induced by low dose-rate radiation can be retained in spleen cells, and could be accumulated in proportion to the total dose, implicating important findings to understand the in vivo mechanisms underlying induction of translocations after exposed to low dose-rate gamma-rays and also to assess the biological risk of exposed to low dose radiation. This work was supported by a grant from Aomori Prefecture, Japan.
