Blood Changes in Irradiated Cotton Rats and Rice Rats

Response of the peripheral blood after irradiation was measured in two species of wild rodents, the radiation-resistant cotton rat (Sigmodon hispidus) and the radiosensitive rice rat (Oryzomys palustris). Blood samples were taken before exposure to 200 or 600 rads and then at periodic intervals after irradiation. Erythrocyte counts, hemoglobin concentrations, and hematocrit percentages were unchanged for the cotton rats at both dose levels and for the rice rats receiving 200 rads. However, rice rats receiving 600 rads developed a severe normocytic anemia by the 13th day after irradiation and died before the 15th day postirradiation. Leukopenia developed in both species and was dose-dependent within each species. Leukocyte counts in the cotton rats receiving 200 rads were less reduced and recovered to normal levels faster than in the group exposed to 600 rads. Similar patterns were noted for the rice rats, but recovery was slower and preirradiation levels were not reached within 30 days. Patterns of reduct...