Effect of repeated whole-body x-irradiation on peripheral white blood cell count of rabbits

¹ Department of Radiobiology and Veterinary Division, School of Aviation Medicine, USAF, Randolph Air Force Base, Texas

Six groups of rabbits received whole-body x-irradiation of 0, 100, 200, 300, 400 and 500 r, respectively. Counts of total white blood cells were performed regularly until 11 weeks post exposure when radiation-induced leucopenia had disappeared in all groups. At that time, the animals were re-exposed to the same doses and white cells were once more counted throughout 11 weeks. Then followed a third application of the same doses with subsequent observation of white counts. Statistical analysis of data yielded the following results: in the three exposures, radiation-induced leucopenia showed no significant difference with respect to rate of development, maximal degree and rate of disappearance. Therefore, as judged by the white blood cell count, susceptibility to ionizing radiation appeared unaltered by previous exposure to appreciable doses when the interval between exposures was sufficiently long to permit complete hematopoietic recovery.