Evidence for the participation of endogenous activin A/erythroid differentiation factor in the regulation of erythropoiesis.

Activin A/erythroid differentiation factor (EDF) is a human protein that induces differentiation of a murine erythroleukemia cell (the Friend cell). In this study, we demonstrate that endogenous activin A/EDF activity is present in murine bone marrow and spleen. In addition, this activity is secreted by bone marrow and spleen cells in primary culture. Administration of follistatin (a specific binding protein for activin A/EDF) to mice results in a decrease of erythroid progenitors in the bone marrow and spleen. These findings support the concept that activin A/EDF and follistatin have opposing actions in the regulation of erythropoiesis.