Nonerythropoietic roles of erythropoietin in the fetus and neonate

Erythropoietin (Epo) is the primary growth factor involved in the regulation of erythropoiesis and was once thought to be unique to the hematopoietic system. Like other cytokines that have been discovered in one system, only then to have unrelated functions attributed to it, Epo has now been found to have nonerythropoietic effects. These effects are mediated by Epo binding to its specific cell surface receptor. Functional Epo receptors are present on many nonerythropoietic cell types. This article reviews the cell types on which the Epo receptor is found, and the nonerythropoietic functions that can be attributed to Epo. Emphasis is placed on the vascular, gastrointestinal, and neurologic effects of Epo.