Studies on Erythropoietin. I. Demonstration of Erythropoietin in Normal Plasma

1. A modification of a technic wherein hypertransfused rats are used for the bioassay of erythropoietin is described, and some kinetics of iron incorporation following transfusion are presented.

2. It was possible to detect activity in normal plasma and demonstrate that plasma of animals whose erythropoiesis is depressed below normal by hypertransfusion possesses less erythropoietin than normal plasma.

3. The variation of response under standardized conditions is sufficiently small and sufficiently predictable so that within certain limits, quantitation is possible. A dose-response analysis is presented.

4. Plasma from normal rats possesses approximately 25 per cent of the activity found in rats rendered acutely anemic by a standardized blood loss.