Radiation dose from plutonium deposited in marrow and bone of normal and chimaeric mice

239Pu citrate was injected intraperitoneally into CBA mice and into CBA mice which had been made chimaeric by replacing their haematopoietic bone-marrow with that from another genetically-identical but cytologically-distinct strain. The mice were killed at three intervals up to 90 days after injection, and the deposited 239Pu was determined radiochemically in bone-marrow and in bone. The average radiation dose (integrated over 90 days) was found to be greater in the bones but lower in the marrow of chimaeric mice than in the corresponding tissues of the normal CBA mice. These results are discussed from the points of view of induction of malignant change in marrow and bone and of plutonium metabolism in the two types of mouse.