Abstract:
Introduction. The main regulator of erythropoiesis is erythropoietin (EP). Erythropoietin is synthesized in
the kidneys, liver, and other organs. The factor that stimulates the formation of erythropoietin is hypoxia
of different etiology (anemia, heart failure, lung failure, massive hemorrhage, erythrocyte hemolysis,
decreased barometric pressure, etc.).
Aim of study. Analysis of data from the available literature regarding the level and mechanisms of action
of erythropoietin in different periods: embryonic, fetal, neonatal and adult.
Methods and materials. Several articles were studied by keywords: erythropoietin, erythropoiesis.
Results. In the intrauterine period the level of EP increases simultaneously with the level of hemoglobin
(Hb) of the embryo, and then of the fetus, which have a higher affinity for oxygen. In the umbilical cord
and in the newborn, the level of EP is much higher than in the blood of the adult, which indicates an
intensification of erythropoiesis. By the second postnatal day, its level decreases as a response of the body
to a radical improvement in tissue oxygenation with the transition to pulmonary respiration. As a result of
the reduction in the level of EP in the first week after birth in the peripheral blood the amount of
reticulocytes also decreases, normoblasts disappear, the percentage of erythrocyte predecessors decreases
dramatically in the red bone marrow, and extramedullary erythropoiesis disappears. The first months of life
are characterized by a low level of EP, but it can vary depending on hypoxia, the concentration being
inversely proportional to the level of Hb. During the second month of life, EP levels increase and are set at
the characteristic level of an adult. There are several mechanisms that ensure the secretion of erythropoietin:
the direct action of the blood with low oxygen partial pressure on the cells that secrete erythropoietin or by
an indirect effect on the activation of the hypothalamic-pituitary-adrenal system which under hypoxia
increases the release of glucocorticoids, catecholamines, stimulates the formation of erythropoietin in the
kidneys by humoral mechanism and thus intensifies the processes of erythropoiesis in the red bone marrow.
Conclusion. The production of erythropoietin is regulated by the degree of oxygenation of the tissues. The
body is able to compensate hypoxemia (regardless of the causes that caused it) with an increase in the level
of EP production. As a result, erythropoiesis is stimulated, and the level of oxygenation of the tissues
increases.
