Fractionated Dose Effects on Survival and Organ Weights in X-Irradiated Mice

¹ From the Radiobiology Department, U. S. Army Medical Research Laboratory, Fort Knox, Kentucky

Intervals between each of five 140-r doses of 1, 3, 5, 7 and 9 hours resulted in survivals of 15, 35, 55, 45 and 40%, respectively, for fractionated total body x-irradiation of mice. A 700-r single dose was 100% lethal. The pattern of the intestinal dry weight response was similar to that for survival. Fractionating the total dose did not seem to significantly alter the 700-r single dose spleen wet weight value. The findings suggest that the fast recovery of the mitotic process and of the nucleic acid metabolism in the small intestine at about 5 hours after irradiation with doses between 100 r and 200 r may be responsible for the observed results for the 5-hour interval fractionated total body x-irradiated mice.