Erythrocyte Fe⁵⁹ Uptake as a Function of Bone Marrow Dose Injected in Lethally Irradiated Mice

The relation between bone marrow cell dose and 24-hour erythrocyte Fe⁵⁹ uptake has been established in lethally irradiated mice. Erythrocyte Fe⁵⁹ uptake is a function of the dose of bone marrow cells and of the time after irradiation at which Fe⁵⁹ is injected. By choosing appropriate bone marrow doses and times of Fe⁵⁹ injection, the range of cell doses between 5 x 10⁵ and 2 x 10⁷ has been explored. The relation between cell dose and Fe⁵⁹ uptake is linear for Fe⁵⁹ uptakes between 0 to 30 per cent. The steepest line relating Fe⁵⁹ uptake to cell dose is that obtained when Fe⁵⁹ was injected at day 9 and covers the range of 5 X 10⁴ to 5 X 10⁵ cells. The curve obtained when iron is injected on day 5 is much flatter and covers the range of 1 x 10⁶ to 2 x 10⁷ cells. Erythropoiesis stimulating factor (ESF) in doses that stimulate erythrocyte Fe⁵⁹ uptake in normal mice has no effect in irradiated, bone marrow-treated mice. Homologous marrow is slightly less effective, and rat bone marrow markedly (∼ 100 times) less effective in promoting recovery of erythropoieis. The erythrocyte Fe⁵⁹ uptake of mice preimmunized with homologous or rat marrow before irradiation is much lower than that of nonpreimmunized animals.