[Capacity of hematopoietic colony-forming cells to maintain their own population in the late periods after prolonged radiation exposure].

The content of multipotent CFUs in bone marrow and their self-maintenance capacity were studied for 15 months following protracted external radiation of CBA mice at the total dose 10 Gy (0.5 Gy per day). The mean life shortening was 16% in the irradiated mice. The proliferating, maturating and functional pools returned to normal within 1-3 months after exposure. The stem cell pool did not return to the values seen in the same age controls till the end of the life of experimental animals and averaged 55% of normal. The self-maintenance capacity of bone marrow CFUs was 2.5-4.5-fold as decreased in the irradiated mice. The failure of this unique property of multipotent CFUs was principally due to the foregoing increase in their proliferative activity.