EFFECTS OF ACTIVIN-A ERYTHROID DIFFERENTIATION FACTOR ON ERYTHROID AND MEGAKARYOCYTIC DIFFERENTIATIONS OF MOUSE ERYTHROLEUKEMIA (FRIEND) CELLS - EVIDENCE FOR 2 DISTINCT MODES OF CELL RESPONSE

To further characterize activin A/erythroid differentiation factor (ED F) action on hematopoietic cell differentiation, we examined the effec ts of activin A/EDF on megakaryocytic and erythroid differentiation by determining acetylcholinesterase (AchE) activity and hemoglobin produ ction in the mouse erythroleukemia (MEL) cell line F55. Activin A/EDF induced AchE activity of F55 cells in a dose-dependent manner. Erythro id differentiation of F55 cells, which was characterized by an increas e in dianisidine-positive cells, was also induced by activin A/EDF. Th e effect of activin A/EDF on hemoglobin synthesis appeared more slowly compared with the effect on AchE activity. Erythroid differentiation induced by activin A/EDF was affected by the initial cell density, but AchE activity was not. Sodium orthovanadate, a tyrosine phosphatase i nhibitor, markedly inhibited activin A/EDF-induced erythroid different iation but not activin A/EDF-induced AchE activity. Other erythroid di fferentiation inducers, sodium butyrate and butyrylcholine chloride, m ildly increased AchE activity in F55 cells, but N,N'-hexamethylene-bis -acetamide (HMBA), dimethyl sulfoxide (DMSO), and genistein did not. D examethasone inhibited HMBA-induced erythroid differentiation but did not affect activin A/EDF or sodium butyrate action. These results sugg est that F55 cells potentially can differentiate into cells of a megak aryocytic Lineage in addition to an erythroid lineage, and that activi n A/EDF further potentiates the cell differentiation of this cell Line . In addition, our results suggest that the mode of activin A/EDF effe cts on megakaryocytic differentiation is distinct from that on erythro id differentiation.