Hematological studies and measurements of plasma iron concentration, plasma copper concentration, total iron-binding capacity, and total plasma protein were carried out in eight control sheep and eight sheep which received 25,000 rads of beta radiation to the skin. Thrombocytosis began at approximately 4 weeks postirradiation and persisted to approximately 18 weeks postirradiation. Lymphocytes and basophils in the irradiated sheep were significantly lower than in the control sheep, while neutrophils and eosinophils were elevated beginning at approximately 8 weeks postirradiation. Mean corpuscular volume decreased and total red cell count increased in the irradiated sheep. Two periods of hypoferremia occurred in the irradiated sheep: one from 2-3 weeks and the other from 8-16 weeks postirradiation. Plasma copper concentration, total iron-binding capacity, and total plasma protein were significantly elevated in the irradiated sheep.

Iron kinetics, red cell mass, and plasma copper were measured in sheep subjected to various combinations of gamma irradiation of the total body and beta irradiation of the skin and gastrointestinal tract. Beta irradiation of the skin, and to a lesser extent of the gastrointestinal tract, produced hypoferremia, a decrease in circulating red cell mass, and hypercupremia. Changes in iron kinetics indicated an increased rate of erythropoiesis. It is suggested that the reduction in red cell mass is caused by an abnormally high rate of destruction of erythrocytes which are damaged as a consequence of circulating through injured tissue. The hypercupremia may be a response to the increased demand for iron necessary for hemoglobin formation.

The data presented led to the following conclusions: (1) there is significant incorporation of tritiated thymidine into all tissues of the mouse after oral ingestion; (2) at least part of this incorporation is not related to mitotic activity; (3) intraperitoneal injection produces greater nonvolatile tissue activities in proliferative tissues than oral ingestion; (4) a radiation effect is produced by levels of tritium activity which deliver a radiation dose to the nucleus that is not greater than 15 rads; and (5) assuming that metabolism is comparable to that in the mouse, a single oral ingestion of 1.0 mCi or less of tritiated thymidine by man would be required to deliver a radiation dose of 1.25 rads over a period of 13 weeks to the nuclei of a significant fraction of cells in the total body.