Constant post-irradiation repopulation rates and linear relationship between cellular blood response and number of transplanted bone marrow cells in inbred mice.

Graded doses of syngeneic bone marrow cells were transplanted into lethally irradiated mice. Repopulation curves of peripheral blood granulocytes and platelets were apparently exponential and parallel after doses larger than 5 X 10(5) cells. The blood platelet Td was reduced from 111 h to 53-57 h, and granulocyte Td from 57 to 40 h in transplanted groups. The mean blood cell counts were reproducible enough to be used as a biological assay of the amount of bone marrow cells transplanted. Linear relationship between increment of blood cells up to day 16 and number of bone marrow cells transplanted on day 1 was demonstrated (1,200 granulocytes and 14,300 platelets/mul blood per 10(5) bone marrow cells). The linearity suggested a mean Td less than 22.5 h of proliferating bone marrow cells, and allowed a rough estimation of mouse bone marrow stem cell radiosensitivity (Do 76 rad).