Characterization of murine erythroid progenitors with high erythropoietin sensitivity in vitro.

The microplasma clot culture system was employed to study the characteristics of late murine erythroid progenitor cells. Erythroid cluster and colony-forming cells (CFUE) were compared with regard to erythropoietin sensitivity, cell-cycle activity, response to hypertransfusion-induced plethora, average cell size, temporal kinetics of in vitro cluster or colony formation, and relative frequency in murine bone marrow. Results indicate that erythroid cluster-forming cells represent a stage of differentiation which is further along the erythroid pathway than CFUE and are nearly 6-fold more sensitive to the hormone.