A Comparison of the Response to Injected Radioactive Phosphorus and to X-rays in the Haematopoietic Tissue of Rats

SummaryThe radiation response of haematopoietic tissue in rats following the administration of 32P is compared with the response to acute whole-body x-irradiation in terms of the radiation dose to different tissues, using thick-section autoradiography for measuring the radiation dose to the bone-marrow in the animals treated with 32P. Changes in the peripheral blood picture and results of 59Fe tracer studies in splenectomized and intact rats are presented.In spite of considerable differences in the conditions of irradiation, a number of similarities in the response of haematopoietic tissue are obtained with these two methods of irradiation. It is suggested that there is little or no dose-rate effect over the range ∼ 30 r/min to ∼ 0·2 rads/min for this tissue. A considerably earlier recovery of erythropoiesis in the spleen after 32P than after x-irradiation is demonstrated.