The cellular biology of erythropoietin receptors.

Long thought to act only as a hormone that was the primary regulator of red blood cell production, erythropoietin is now known to have a whole spectrum of activity. Organs such as the brain, ovary, oviduct, uterus, and testis have erythropoietin receptors. Because erythropoietin receptors exist in the paracrine and autocrine systems, as well as the hormonal system, the beneficial effects of administering human erythropoietin are likely to extend beyond its effect in raising hematocrit. It may even be possible in the future to use the receptors to target a drug to a tumor without damaging the surrounding tissue.