Response of Rats of Various Ages to Erythropoietin. ∗

Abstract

Conclusions

Erythropoietin of human urinary origin was injected into groups of rats of various ages, after which both measurements of total circulating red cell volume and Fe⁵⁹ red cell incorporation were made. Total red cell volume of young rats throughout the period of neonatal anemia did not increase in response to administration of erythropoietin, whereas it did increase in all older groups. According to this assay, the rat most sensitive to erythropoietin was the oldest rat studied. Using the Fe³⁹ red cell incorporation assay, no increase in erythropoiesis was observed in normal young rats(14 days of age) following erythropoietin administration. However, when erythropoiesis was depressed in young rats by hypertransfusion. red cell uptake of Fe⁵⁹ was greatly reduced. When such hypertransfused rats were injected with erythropoietin, red cell incorporation of Fe⁵⁹ was significantly increased.