Temporal and spatial response of marrow colony-forming cells (CFU-s and CFU-c) after ²²⁶Ra incorporation in BALB/c mice

The numbers of hemopoietic cells (CFV-s and CFU-c) were assayed by colony tests at different times after injection of either 230 or 660 kBq ²²⁶Ra/kg in BALB/c mice. Assays were performed for marrow sites surrounded by trabecular bone (distal end of femur, lumbar vertebra, sternum) and for the femoral diaphysis where axial marrow and marrow near cortical bone were examined separately. The response in number of CFU-s and CFU-c from various marrow sites varied remarkably. Radiation-induced hemopoietic changes were not strictly related to the surrounding trabecular or cortical bone structure. The number and concentration of CFU-s and CFU-c were most altered in marrow sites which contained a high proportion of CFU-s in DNA synthesis. Fewer alterations in the number of hemopoietic cells were noticed after injection of 230 kBq ²²⁶Ra/kg than after 660 kBq ²²⁶Ra/kg. After 230 kBq ²²⁶Ra/kg bone marrow cellularity and the number of CFU-s and CFU-c frequently increased above the control level, while after 660 kBq ²²⁶Ra/kg only depressions below the control level occurred.