Erythropoietic precursors in murine blood.

Murine blood was examined for circulating erythropoietic precursors. Blood mononuclear cells harvested using a slight modification of the Ficoll-Hypaque technique were cultured using the methylcellulose clonal cell culture technique. Only erythropoietic burst forming units (BFU-E) were present in the blood. Erythropoietin dose response studies revealed a progressive increment in the number of erythropoietic bursts up to a concentration of 4 U/ml of sheep plasma erythropoietin. A linear correlation existed between the numbers of nucleated cells plated and the erythropoietic bursts for both normal mice and mice with phenylhydrazine-induced (PHZ) anemia. No individual erythrocytic colonies were detected in cultures from blood taken before or after PHZ injections. These results suggest that erythrocytic colony-forming units (CFU-E) do not participate in the migration of erythropoietic precursors in mice.