On the mechanism of erythropoietin-induced differentiation. 8. The effect of iron on stimulated marrow cell functions

Inhibition of heme synthesis in bone marrow cells by succinylacetone: effect on globin synthesis

The effects of 4,6-dioxoheptanoic acid (succinylacetone, SA), an inhibitor of delta-aminolevulinic acid dehydratase, on total iron uptake, heme synthesis, and globin synthesis were studied in rat marrow cells in culture in order to examine the coordination of heme and globin synthesis. SA inhibited heme synthesis in both control and erythropoietin-stimulated cells in a dose-dependent fashion; at 10(-3) M, inhibition was complete, whereas at 10(-7) M, there was no significant effect. Inhibition of total iron uptake was also dose-dependent although, at 10(-3) M, it was not complete. The inhibition of heme synthesis by SA was partially overcome by addition of 10(-4) M porphobilinogen or protoporphyrin IX. SA caused an almost complete suppression of globin formation in both erythropoietin-stimulated and unstimulated cells as early as five hours after the addition of the inhibitor. When inhibition of heme synthesis was incomplete, globin synthesis was partially inhibited. These results indicate that heme synthesis is required for erythropoietin-mediated induction of globin synthesis in cultured bone marrow cells.

Specific enhancement of mouse CFU-E by mouse transferrin

Pure human and mouse transferrins were prepared by a chromatographic procedure and their effect on the growth of early (BFU-E) and late (CFU-E) erythropoietic precursors in mouse bone marrow is described. In the presence of optimal erythropoietin concentrations mouse bone marrow cells have a greater specificity for mouse transferrin (950 CFU-E colonies/10(5) cells) than human transferrin (650 CFU-E colonies/10(5) cells). Optimal transferrin concentrations for both human and mouse transferrins were 1.3x10(-13)M and 1.3x10(-10)M corresponding to between 7.8x10(7) and 7.8x10(10) molecules/ml of culture. These concentrations are in excess of that calculated on a theoretical basis. Neither erythropoietic burst nor granulocyte/macrophage colony formation exhibited a dose dependent relationship for any of the transferrins employed, although higher colony numbers were obtained with mouse transferrin compared to human transferrin.