Lymphocyte depletion in peripheral blood of acutely gamma-irradiated rats

Groups of albino rats were exposed to 200, 800, 2000 and 5000 R of 60-Co gamma-radiation. Peripheral blood samples were taken from the tail at 1, 2, 4, 8 and 24 hours after irradiation. Calculation of the lymphocyte count per unit blood volume was made for each sample. Control rats were also mock-irradiated and sampled in the same manner. The time response of the lymphocyte count indicated that within the first hour, there was a drastic prompt drop. From one to eight hours after irradiation, the counts declined continuously, and from eight to twenty-four hours less rapidly. The depletion rates for the one to eight hour period were calculated and found to be statistically different for all groups, except between 2000 and 5000 R.