Effect of mass blood-transusion on erythroid cell differentiation in anemic rabbits. II. Denucleation in the early stage of erythroid cell specialization, with special reference to RNA- and hemoglobin synthesis

For the purpose of settling the specialization stage of erythroblast where the transcription for hemoglobin is initiated, the absorption of heme and the incorporation of tritiated uridine into RNA have been observed on the cells from the anemic rabbit after a mass red cell transfusion by which the DNA synthesis of large size precursors is suppressed and the early denucleation of erythroblasts is stimulated. In the erythroblasts obtained 24 to 72 hours after red cell transfusion a distinct absorption of heme appears first in the proerythroblast, followed by a progressive increase with the advance of the specialization. Hemoglobin synthesis is markedly stimulated after the denucleation. The incorporation of tritiated uridine into RNA is most marked in the proerythroblast and decreases with the advance of specialization stage suggesting that the mRNA synthesis for hemoglobin is initiated at the proerythroblast, continuing to the polychromatic erythroblast where. the synthesis is minimized. The volumetric observations indicate a possible denucleation at proerythroblast, but it has been revealed that the maximum RNA level of macrocytes is comparable to that of early basophilic erythroblast and its highest hemoglobin level is only that expected in the cells denucleated at late basophilic stage. From these observations it has been concluded that the transcription for hemoglobin is triggered at the initial step of erythroid cell specialization, proerythroblast, but it is insufficient for the synthesis of the expected amount of hemoglobin and is compensated or completed by the mRNA synthesis in more advanced stage of specialization.