Erythropoietin gene expression in macrophages detected by in situ hybridization.

The signal for erythropoietin (epo) production is partial oxygen tension. Erythropoietin release from cultured macrophages, derived from unstimulated and unseparated mouse bone marrow cells, occurs in response to changing physiological oxygen concentrations. In situ hybridisation, using biotin-labelled epo DNA demonstrated epo gene expression in both in vitro-derived and in vivo macrophages. The results indicate that epo production occurs locally at the sites of erythropoiesis.