title: Dose-rate effects and dose and dose-rate effectiveness factor on frequencies of chromosome aberrations in splenic lymphocytes from mice continuously exposed to low-dose-rate gamma-radiation.
abstract: Dose-rate effects on chromosome aberrations in the low-dose-rate range have not been evaluated previously. The incidences of chromosome aberrations were analysed in splenic lymphocytes from female specific pathogen-free (SPF) C3H mice that were continuously irradiated with low- or medium-dose-rate (LDR, MDR) (137)Cs γ rays from 56 days of age to evaluate the dose-rate effects. The dose-response relationship for the frequency of dicentric chromosome aberration at each dose rate (400 mGy/22h/day, 20 mGy/22h/day and 1 mGy/22h/day) was obtained using age-adjusted multiple linear regression analysis assuming that the relationship can be represented by a linear or linear quadratic model and a test for the difference between the irradiated group and the non-irradiated group. Values of the linear term, shown as the slope, decreased as the dose rate was reduced from 400 mGy/22h/day (18.2 mGy h(-1)) to 1 mGy/22h/day (0.045 mGy h(-1)), indicating a positive dose-rate effect in the dose-rate region. The incidences of dicentric chromosomes and translocation for LDR (20 mGy day(-1)) were compared with those for HDR (890 mGy min(-1)) irradiation at each total dose to obtain the dose and dose-rate effectiveness factor (DDREF). The DDREFs were 4.5 for dicentrics and 2.3 for translocations at a total dose of 100 mGy based on the chromosome aberration rate. These results will be useful for estimating the risk of LDR radiation exposure and radiation protection.
authors.affiliation: Department of Radiobiology, Institute for Environmental Sciences (IES), 2-121 Hachazawa, Takahoko, Rokkasho, Kamikita, Aomori 039-3213, Japan. kmtanaka@ies.or.jp
authors.forename: Kimio
authors.initials: K
authors.lastname: Tanaka
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kohda
authors.forename: Kenichi
authors.initials: K
authors.lastname: Satoh
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000187:drug effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D008214:Lymphocytes / Q000502:physiology* / Q000528:radiation effects*; D051379:Mice; D008809:Mice, Inbred C3H; D011829:Radiation Dosage; D013154:Spleen / Q000166:cytology / Q000502:physiology / Q000528:radiation effects; D014916:Whole-Body Irradiation