The relationship of hemoglobin synthesis to erythroid colony and burst formation

We have demonstrated that the cyclohexanone method for the extraction of hematin can be used to measure hemoglobin synthesis induced by erythropoietin (epo) in mouse bone marrow cells cultured in medium containing methyl cellulose. The time course of hemoglobin synthesis by mouse marrow cells showed two effects due to epo: an increase in hemoglobin synthesis at day 2, which corresponded to the formation of small erythroid colonies resulting from the CFU-E (colony-forming unit, erythroid), and a very large increase in hemoglobin synthesis, which was maximal at days 7–8 and corresponded to the formation of large erythroid colonies (bursts) resulting from the BFU-E (burst-forming unit, erythroid). The epo dose-response curves for CFU-E colony counts and day-2 hemoglobin synthesis were similar, and the cell-number- response curves for these two paramaters were parallel. The epo dose- response curve for BFU-E colony counts reached a plateau at an epo concentration between 3 and 5 units/ml, whereas the dose-response curve for 6–8-day hemoglobin synthesis did not reach a plateau even at an epo dose of 10 units/ml.