Factor with erythroid burst-promoting activity in human urine unlike other hematopoietic growth factors

A factor with burst-promoting activity (BPA) stimulates the formation of erythroid bursts in the presence of erythropoietin, acting on early erythroid progenitor cells (erythroid burst-forming units, or BFU-E). Here we investigated the biological properties of this factor partially purified from the urine of anemic patients. The human urinary factor did not cause the formation of late erythroid progenitor cells (erythroid colony-forming units, or CFU-E) or enhance such colony formation in the presence of erythropoietin. Thus, the urinary factor was a different substance from erythroid potentiating activity and from activin, which act on both BFU-E and CFU-E. The urinary factor promoted the colony formation of BFU-E from both humans and mice, but the human hematopoietic growth factors such as recombinant interleukin-3, interleukin-6, granulocyte-macrophage colony-stimulating factor, and macrophage colony-stimulating factor did not stimulate the formation of BFU-E derived colonies from mice. The results suggested that the factor in the urine of anemic patients was different from the hematopoietic growth factors identified so far.