Comparative effects of exposure of the mouse to radiation at constant and changing dose rates

Two sublines of strain RFM mice with different radiation-resistance characteristics were exposed to equivalent, repeated, 46.4-hr continuous gamma-ray treatments, some groups at a changing dose rate and others at a fixed dose rate. Three dose-rate levels between approximate means of 2–5 rads/hr were studied. Changing dose rates were more biologically damaging than were equivalent, constant dose rates. There were differences in substrain radiation resistance to all exposure conditions.