[The effect of cyclophosphamide on the erythropoietic stem cell compartment]

The recovery of erythroid committed percursor cells and pluripotent haemopoietic stem cells (CFU-S) was determined in polycythaemic mice treated with cyclophosphamide (Cy). Erythroid repopulating ability (ERA) of bone marrow cells, erythropoietin responsive cells (ERC) and CFU-S were estimated for 4, 8 and 7 days after treatment with 200 mg/kg b. w. Cy, respectively. The proliferation rate of CFU-S and erythroid repopulating cells (ERA cells) was followed at the same time on the basis of cytosine arabinoside suicide data. The results demonstrated the difference in CFU-S and ERA regeneration. ERA recovery preceded CFU-S regeneration at the time when ERC were severely depressed. The proliferation rate of CFU-S and ERA cells differed also during the regeneration after Cy. The results suggest contribution of erythroid committed cells that proceed ERC (preERC) in measurement of ERA in polycythaemic mice treated with Cy.