STIMULATORY EFFECT OF HUMAN INSULIN ON ERYTHROID PROGENITORS (CFU-E AND BFU-E) IN HUMAN CD34-MARROW CELLS AND THE RELATIONSHIP BETWEEN INSULIN AND ERYTHROPOIETIN( SEPARATED BONE)

Erythropoietin is known to be effective for the treatment of anemia in chronic renal failure, but the efficacy of erythropoietin for anemia in other diseases is not so great. Insulin exerts a growth promoting a ctivity in various kinds of cells. In the present study, the effects o f insulin on erythroid progenitors (colony forming units-erythroid, CF U-E; and burst forming units-erythroid, BFU-E) in human bone marrow we re examined at various concentrations of recombinant human erythropoie tin (rh-Epo) to clarify the relationship between erythropoietin and in sulin. Human insulin stimulated the formation of CFU-E and BFU-E in th e presence of three concentrations (0.25, 5, and 100 U/ml) of rh-Epo. Stimulatory effects of human insulin on CFU-E and BFU-E were also obse rved in the nonphagocytic and nonadherent bone marrow fraction (NP-NA fraction) and in the NP-NA and T cell-depleted fraction at each concen tration of rh-Epo. Human insulin further stimulated the CFU-E and BFU- E growth in CD34+ separated bone marrow cells. These results indicate that the enhancing effect of human insulin on erythroid progenitors is not mediated through monocytes and macrophages or T cells, suggesting a direct action on erythroid progenitors.