The transfusion-induced polycythemic mouse is an excellent subject in which to study the physiology of erythropoiesis because endogenous erythropoiesis is reduced in a manner that does not appear to impair, to any recognizable degree, the animal’s ability to respond to an erythropoietic stimulus.
Using a purified glycoprotein, erythropoietin, obtained from the plasma of anemic sheep, a number of experiments was carried out on polycythemic mice. Morphological evidence of erythropoiesis in the spleen was observed following a single subcutaneous injection of erythropoietin. A cumulative response to multiple injections was noted. For a given total dose of erythropoietin, a greater response was produced when this amount was fractioned than when it was administered as a single dose. Animals made polycythemic by transfusion were maintained in a polycythemic state by daily injections of erythropoietin. Finally, a true erythrocytosis was produced by a prolonged course of injections of erythropoietin in normal mice.