Effects of Erythropoietin on 14 C-Formate Uptake by Spleen and Bone Marrow Nucleic Acids of Erythrocyte-Transfused Mice. ∗

Abstract

Summary

The effect of erythropoietin on the incorporation in vivo of ¹⁴C-formate into the nucleic acid of spleen and bone marrow of erythrocyte-transfused mice has been investigated. Erythropoietin increases the specific activity of nuclear and cy toplasmic RNA between one and two hours after injection of the hormone. Specific activity of nuclear RNA remains high for 74 hours while that of cyto-plasmic RNA drops between 50 and 74 hours after EP administration. Specific activity of DNA begins to increase slowly at 8 hours and then more rapidly at 26 hours after EP to reach a maximum at 50 hours. Experiments with inactive erythropoietin suggest that the effect on nucleic acid metabolism is due to the hormone and not to other substances contained in the erythropoietic preparations. In a condition such as that of erythroid tissue of the transfused mouse, where only the differentiating effect of EP is being studied, the earliest effect observed is an increase of the uptake of ¹⁴C-formate into nRNA, followed later by increased uptake into DNA, which presumably reflects the increase of erythroid cells in S phase during the erythropoietic wave that follows EP injection. Further studies are required to determine the nature and significance of the RNA synthesized, soon after EP injection.

We should like to thank Professor G. Hodgson for valuable discussions, suggestions and for preparation of the manuscript. Also the authors wish to acknowledge the skillful technical assistance of Mr. Fernando Garrido.