Radiosensitivity and proliferative activity of vertebral CFU-S surviving in mice injected with oncogenic activities of 239Pu or 241Am.

Survival, radiosensitivity and capability to produce differentiated progeny were followed in CFU-S from lumbar vertebrae of mice injected with 198.6 kBq 239Pu/kg or 208.6 kBq 241Am/kg. The CFU-S assay and 59Fe uptake into spleen colonies were used. The number of CFU-S from treated mice was significantly lower than in controls. Higher radiosensitivity of CFU-S from 239Pu- or 241Am-treated mice was demonstrated using additional exposure to 0.5 Gy X-rays 1, 24, 48, 72 hrs after cell transplantation and expressed more precisely by survival curves obtained 1 hr after the marrow cell injection. The effect of 239Pu on CFU-S was characterized by Do 0.58 Gy (n = 0.91) and that of 241Am by Do 0.64 Gy (n = 0.91); corresponding control values were Do 0.89 Gy, n = 1.11. Lower iron utilization due not only to the decreased CFU-S numbers, but also to the defective production of erythroid cells per one CFU-S was found. Complexity of radiation effect on hemopoietic stem cells was demonstrated by the present study.