Radiation Responses of Hemopoietic Colony-Forming Cells Derived from Different Sources

Abstract

Hemopoietic colony-forming cells derived from adult femoral marrow, adult spleen, and fetal liver of mice did not exhibit a uniform sensitivity to ionizing radiation when freshly explanted cells from these sources were tested for survival of colony-forming ability after irradiation in vivo. The Do values and extrapolation numbers observed were: for adult femoral marrow, 95[plus or minus]9 rads, 1.50 [plus or minus] 0.54; for adult spleen, 90 [plus or minus] 16 rads, 0.80 [plus or minus] 0.46; for fetal liver, 146 [plus or minus] 26 rads, 1.08 [plus or minus] 0.50. However, 14 days after transplantation into x-irradiated (900 rads) isologous hosts, hemopoietic colony-forming cells derived from each of these sources showed a relatively uniform, increased radiation sensitivity. The Do values and extrapolation numbers for cells proliferating in the spleens of the irradiated hosts were: for cells derived originally from marrow, 69 [plus or minus] 12 rads, 0.99 [plus or minus] 0.42; for cells derived from spleen, 74 [plus or minus] 15 rads, 0.77 [plus or minus] 0.43; for cells derived from fetal liver, 80 [plus or minus] 16 rads, 0.72 [plus or minus] 0.42. For cells derived from fetal liver, the increase in radiation response took place during the first 6 days after transplantation of the cells into irradiated hosts. It is suggested that the properties of colony-forming cells in different hemopoietic tissues are not uniform, and that the change in radiosensitivity observed represents a change in the properties of colony-forming cells due to transplantation into irradiated hosts.