EARLY FLUCTUATIONS OF ERYTHROPOIETIC BURST FORMING UNITS E POOL SIZE AFTER TRANSFUSION OR ERYTHROPOIETIN TREATMENT

The kinetics of erythroid burst-(BFU-E) and colony-forming units (CFU-E) were evaluated in marrow and spleen of normal or polycythemic mice, respectively, after transfusion or administration or purified erythropoietin (Ep). Ep injection induced an early but temporary rise of BFU-E number vs. a later but more prolonged expansion of the CFU-E pool. Symmetric patterns were observed after transfusion, i.e., an early but transient depletion of the BFU-E population, vs. a later but more persistent decrease of the CFU-E number. The size of the BFU-E compartment is apparently Ep-dependent in the early phase after erythroid perturbation. Compensatory mechanisms allow the BFU-E pool to escape from the early Ep influence, thus allowing its size to return to and stabilize in the near normal range. The BFU-E may represent an early target cell of Ep stimulus.