About Erythropoietin :
Erythropoietin is commonly referred to as hematopoietin or hemopoietin. It is also known in its abbreviated form of EPO. This is a glycoprotein cytokine that’s primarily secreted by the kidney. This secretion takes place as the result of cellular hypoxia. This is a condition in which a part of the body doesn’t receive as much oxygen as it needs. The most common causes of hypoxia in cells is anemia. As a result, people suffering from anemia are found to have increased levels of EPO.
The consequence of EPO secretion is the stimulation of red blood cell production in bone marrow. Everybody constantly has a low level of EPO secreted throughout their body, to act as compensation for regular red blood cell turnover.
The primary function of erythropoietin is to produce more red blood cells. If bodies lack EPO, then the process in which red blood cells are produced cannot take place. The kidney produces EPO when hypoxic conditions are present in cells. EPO is found to have most of its effect in the bone marrow of humans, as this is where red blood cell precursors and progenitors are found. It works to protect these cells from death.
Aside from the function of EPO on red blood cell production, there are other functions linked to it. These include stimulating angiogenesis (the process in which new blood vessels are created from pre-existing ones), vasoconstriction-dependent hypertension, and improving cell survival through activating EPO receptors.
EPO has received a lot of attention in the modern world of athletics as performance-based athletes have attempted to manufacturer an increase in EPO production within their cells. This would boost the oxygen levels in their blood, thereby increasing red blood cell production and helping with endurance.
Mechanism & Interaction
Erythropoietin completes its functions by binding to its receptor; EpoR. EPO must bind with EpoR while on the red blood cell progenitor surface. In doing so, this leads to the activation of a JAK2 signaling avalanche. Following this, the STAT5, PIK3 and Ras MAPK pathways are initiated too.
The consequence of this is differentiation, as well as the survival and multiplication of the erythroid cell. Increased levels of EpoR expression are often confined to the erythroid progenitor cells.
EPO is produced by fibroblasts present in the kidney. These fibroblasts are closely linked with the peritubular capillary and proximal convoluted tubule. EPO can also be found in the perisinusoidal cells within the liver. It is found that liver production mainly occurs in pregnant women during the perinatal period. On the contrary, production via the kidneys is the most common production found in all humans during adulthood.
Levels of EPO in the blood are naturally very low, unless anemia is present. It is thought that the production of EPO can multiply by 1000 when cells are suffering from anemia.
EPO is a glycoprotein weight approximately 30,400 daltons. 165 amino acids are being produced by this protein; primarily via the kidneys and liver. EPO will bind on a certain membrane receptor, which in turn activates multiple signalling pathways.