The Cellular Basis of Differential Radiosensitivity of Normal and Genetically Anemic Mice

The hematological reactions of radioresistant normal ww mice and of extremely radiosensitive WW/sup v/ were followed during a 30-day period after 200 r of whole-body irradiation. Although the normal mice showed only minor changes in the peripheral erythrocyte level, the anemic mice suffered prolonged extreme reduction in hematocrit level, persisting through at least 16 days after irradiation. Reticulocytes disappeared completely from the peripheral blood of WW/sup v/ anemic mice for almost 15 days but were always present in the blood of normal ww mice. Normal ww and anemic WW/sup v/ mice suffered similar destruction of marrow, with effects observable during the first 2 days after irradiation. Marrow regeneration occurred rapidly in normal mice, with great increases in cellularity between the second and fourth days after irradiation. By the eighth day, marrow from irradiated normals could not be distinguished from control normal marrow. Marrow regeneration was greatly delayed in ww mice. Slight evidence of the beginning of regeneration could be seen on the eighth day after irradiation, followed by increasing cellularity and regional repopulation at 12 and 16 days. By day 23, marrow cellularity of andemics approached pretreatment levels. Anemic and normal mice showed the same postirradiation changes in lynnphocyte numbers andd the same reduction in neutrophile numbers. The anemic mice showed some delay in neutrophile replenishment. The genetic difference in radiosensitivity between normal ww and anemic WW/sup v/ mice is caused very largely by their differential rates of regeneration of erythropoietic tissue. (auth)