Radiosensitivity of mouse myeloid stem cells in culture after stimulation by macrophage colony-stimulating factor.

Bone marrow/CFU-C/Macrophage CSF/Radiosensitivity Mouse bone marrow cells were plated in a semi-solid medium containing an excess amount of macro phage colony-stimulating factor (M-CSF). The stimulated macrophage colony-forming cells (CFU-M) took about 40 hours before dividing into two cells. X-Ray irradiation of the cells shortly after plating decreased the survival of CFU-M, while the quasithreshold dose (Dq) and the 37% dose slope (Do) of the dose-response curve were 0.54 Gy and 1.27 Gy. Irradiation 5-50 hours after plating decreased CFU-M survival to the same extent as irradiation shortly after plating. Furthermore, the survival rate of CFU-M was similar to the above when the cells were irradiated in a liquid medium containing no M-CSF. These results suggest that the radio sensitivity of CFU-M does not notably change after their stimulation by M-CSF.