Mutagenic effects of repeated small radiation doses to mouse spermatogonia I. Specific-locus mutation rates

Abstract

When male mice were given repeated small daily doses of 10 rad γ-rays at high dose rate (17 rad/min) the yield of specific-locus mutations was less than when the same total dose (600 rad) was given in a single exposure, and about the same as that after irradiation at low dose rate (0.008 rad/min). However, when a similar total dose was split into doses of 50 rad at weekly intervals the results depended on dose rate. The mutation rate after 12 × 50 rad X-rays at 66–70 rad/min was not significantly different from that after a single exposure, whereas the mutation rate after 12 × 50 rad γ-rays at 0.06 rad/min was typical of low dose-rate irradiation. This confirms that the effect of dose rate on mutation rate does not depend on continuity or close spacing of the exposures. However, it is suggested that the “small dose” effect depends both on size of each dose and on close spacing of doses.