Effect of Erythropoietin on the Peroxidase and Tyrosine-Iodinase Activity of Mouse Thyroid and Submaxillary Gland

During an attempt to explore the mechanism of cobalt and vitamin B 12 effect on the peroxidase and tyrosine iodinase activity, it was observed that cobalt and not vitamin B 12 in vivo elicits a high plasma titer of a humoral factor, erythropoietin, which caused increased 59 Fe incorporation into red blood corpuscles. This erythropoietin was extracted from plasma or kidney and partially purified. This partially purified erythropoietin preparation when injected into starved rat caused increased 59 Fe incorporation into red blood corpuscles. The potency of the partially purified erythropoietin preparation from plasma and kidney was compared. This partially purified erythropoietin, as well as sheep step-I erythropoietin, when administered to mice gave rise to a response almost similar to cobalt administration. It appears that the effect of cobalt on the peroxidase or tyrosine iodinase activity might be mediated through the elevation of the erythropoietin titer of plasma. Moreover, this erythropoietin was found to stimulate both peroxidase and tyrosine iodinase activity of the enzyme preparation of submaxillary gland in experiments in vitro. Erythropoietin, purified further in our laboratory, also produced the same effect. Neuraminidase-treated erythropoietin, in contrast, failed to execute any such stimulatory effect on the iodination of tyrosine.