Factors Stimulating Erythropoiesis in Frogs

1. Sublethal levels of hypoxia do not stimulate erythropoiesis in the frog as measured by the incorporation of thymidine-2-C¹⁴ into peripheral erythrocytes, whereas bleeding of approximately one-third of the blood volume increases erythropoiesis 70-fold as judged by this criterion. This is taken as evidence that for the frog, the fundamental stimulus for erythropoiesis may not be hypoxia.

2. Cobaltous ion administration does not increase erythropoiesis in the frog.

3. The serum of bled frogs increases the incorporation of thymidine-2-C¹⁴ into the erythrocytes of frogs into which it is injected. This serum does not stimulate erythropoiesis in the polycythemic mouse. Serum from an anemic patient which contains large amounts of erythropoietin as measured in the polycythemic mouse does not stimulate erythropoiesis in the frog.