Mechanism of Erythropoietic Action of Thyroid Hormone. ∗

Abstract

Summary

Hypertransfusion polycythemia in mice abolished the erythropoietic effect of T₃, but it was restored when polycythemic mice were exposed at 300 mm Hg ambient pressure. Combined injections of T₃ and erythropoietin had no greater erythropoietic effect in plethoric mice than erythropoietin alone. Results indicate that T₃ does not induce stem-cell differentiation, does not augment the rate of stem-cell differentiation at a given erythropoietin level, and does not increase proliferation of erythroid cells directly. Suppression of erythropoietin formation by bilateral nephrectomy in rats confirmed these results. Absence of erythropoietic effect in two experimental models with suppressed erythropoietin formation makes it improbable that erythropoietic effect of T₃ is exerted by an intermediate other than erythropoietin.