[Genetic effect of chronic gamma radiation exposure in male mice]

The frequency of reciprocal translocations (RT) in mouse spermatogonia induced by gamma-rays at doses of 1.5 to 4.5 Gy and dose rates of 2.7 X 10(-6), 5.8 X 10(-6), 9.4 X 10(-5) and 4.5 Gy/min was studied. A linear increase was observed in the RT frequency with increasing the dose, at all dose rates. At 9.4 X 10(-5) Gy/min the RT frequency was, on average, 10 times lower, as compared to that for a single acute dose rate of 4.5 Gy/min. Further reduction of the dose rate did not result in a decrease of the RT yield, and at the lowest dose rate of 2.7 X 10(-6) Gy/min (the dose being 3.0 Gy) the RT frequency was higher than using the same dose at dose rates of 5.8 X 10(-6) and 9.4 X 10(-5) Gy/min. Possible reasons for an increase in the RT frequency at low dose rates are considered. A study of the frequency of abnormal sperm heads (ASH) has shown that at the dose rate of 9.4 X 10(-5) Gy/min it is independent of an accumulated dose and is equal to the value obtained when exposing to an acute dose of 3.0 Gy. At dose rates of 2.7 X 10(-6) and 5.8 X 10(-6) Gy/min ASH frequencies were only slightly increased at all doses, as compared to the control level.