Erythropoietic Stem Cell Recovery in Irradiated Polycythemic Dogs
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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The response of erythropoietic stem cells in postirradiated polycythemic dogs to 300 units of administered exogenous erythropoietin was measured. One week prior to irradiation the dogs were made polycythemic by transfused allogeneic erythrocytes. The dogs were subjected to 150 rads of mixed gamma-neutron radiation. On the day of irradiation or on 10 different days during the first 3 weeks postirradiation, erythropoietin was administered and the 59Fe incorporation in response to this stimulation was measured. Recovery of the erythropoietic stem cells occurred in an oscillatory manner. In general, this was ascribed to a possible slow rate of differentiation of erythropoietin responsive cells from multipotential stem cells and a more rapid rate of proliferation of the former cells into subsequent erythrocytic progeny. As the number of divisions resulting from each cell is limited, recovery in number of cells is halted or even decreased until more cells from the slower moving multipotential stem cell compartment are released. Contributions to this oscillatory recovery pattern by chalones or the competition of related blood cell lines for the common stem cells, however, have not been excluded.