The effect of erythropoietin on the mature burst forming unit erythroid in mice.

The aim of the study was to further delineate the erythropoietin (Ep) dependence of the mature Burst Forming Unit-Erythroid - BFU-E(d4). Experiments were performed in normal and polycythemic CBA mice. BFU-E(d4) were determined by means of the methylcellulose culture technique. It was demonstrated that in plethoric mice the number of BFU-E(d4) is reduced from 9 000/femur and 30 000/spleen found in normal mice to less than 1 000/femur and 2 000/spleen on day 6 post-hypoxia. The number of BFU-E(d4) remained low both in the bone marrow and spleen in mice with posthypoxic polycythemia between days 6 and 11 post-hypoxia. When exogenous Ep was injected into the plethoric mice the number of BFU-E(d4) increased after 24 h both in the bone marrow and spleen. In Ep stimulated polycythemic mice the CFU-E:BFU-E(d4) ratio did not achieve normal values, indicating that although Ep stimulation increased the number of BFU(d4), the number of CFU-E produced per BFU-E(d4) was lower than in normal nonpolycythemic mice. The results obtained indicate that BFU-E(d4) population size depends on the effect of Ep on differentiation and proliferation of erythroid committed precursors.