The unipotential stem cell, “sensitive” to erythropoietin, gives by division a proerythroblast and a new stem cell in order to maintain normal supply of the cells in the bone marrow.
The synthesis of DNA and RNA in the proerythroblast phase is pronounced
In nucleoli of these cells, RNA are formed necessary for the synthesis of proteins (globin and enzyme) on polysomes of the cytoplasm of erythroblast.
Proerythroblast’s cytoplasm has a lot of ferritin and mitochondria.
Large amount of RNA gives distinct basophilic appearance to the cytoplasm.
Decrease in the RNA synthesis results in the change of the cytoplasm color from polychromatophilic erythroblast to acidophilic erythroblast.
In polychromatophilic erythroblast the nucleus is very small. The synthesis of hemoglobin increases. Ferritin accumulates as hemosiderin.
After dividing of the polychromatophilic erythroblast into acidophilic erythroblast, there is no mitosis any more.

Acidophilic erythroblasts have distinct picnotic nuclei. Their acidophilic cytoplasm has only some organelles (ribosomes and mitochondria). At this stage, the syntheses of DNA and RNA stop, and acidophilic erythroblasts cannot divide any more. Very likely the hemoglobin causes the inhibition of the nucleus activity. When hemoglobin reaches a certain concentration in the cytoplasm, it travels to the nucleus and binds to nucleohistones, thus inactivating the chromosomes. Besides, high concentration of hemoglobin can also inactivate erythropoietin.

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