Insulin-like growth factor I stimulates human erythroid colony formation in vitro.

The effects of human GH and insulin-like growth factor I on the proliferation and differentiation of erythroid progenitor cells from the bone marrow and peripheral blood of children were studied in a hormone-depleted culture system. Growth of erythroid progenitors was quantified by directly scoring colonies and by biochemical determination of the activity of a cytosolic enzyme of the heme pathway, uroporphyrinogen I synthase. In the presence of erythropoietin, high concentrations (50-100 ng/mL) of human GH induced an increase in the number of erythroid colonies (and their uroporphyrinogen I synthase activity) formed by bone marrow or peripheral blood erythroid precursors. In the same conditions, physiological concentrations of insulin-like growth factor I (0.5-1 ng/mL) stimulated erythroid cell growth and differentiation (P less than 0.03) from bone marrow or peripheral blood.