As is known, red blood cells (RBCs) transport oxygen to the tissues and in endurance sports, such as cycling, cross-country skiing, etc., the oxygen requirements are very high.
For some time, therefore, strategies have been investigated to increase the production of RBCs in order to improve sports performance.
The most recent strategy is based on the role of erythropoietin (EPO) in stimulating the bone marrow to produce red blood cells (RBCs).
Recombinant human EPO (rHuEPO) and related substances (eg darbepoietin) are used as doping.
EPO has a relatively short life span in the body while its stimulating effect can last up to two weeks
d "oxygen1985 Lin and Jacobs cloned the erythropoietin gene and developed a transfected cell line (CHO cells) capable of producing recombinant human erythropoietin
Erythropoiesis and hypoxia
Erythropoiesis (production of new red blood cells) is controlled by a very sensitive feedback system, in which a sensor in the kidney senses changes in oxygen supply.
The mechanism is based on the presence of a heterodimeric transcription factor (Hypoxia-inducible factor, HIF-1) (HIF-1α and HIF-1β) which increases the expression of the erythropoietin gene.
HIF-1α is unstable in the presence of oxygen and is rapidly degraded by prolyl-hydroxylase with the contribution of the von Hippel-Lindau protein.
During hypoxia propyl-hydroxylase is inactive consequently HIF-1α accumulates activating the expression of erythropoietin which stimulates the rapid expansion of erythroid progenitors.
(but the first 27 are split during secretion).
It is produced mainly by the peritubular interstitial cells of the kidney, under the control of a gene located on chromosome 7.
After secretion, erythropoietin, in the hematopoietic tissue (bone marrow), binds to a receptor (EPO-R) located on the surface of the erythroid progenitors and is internalized.
In the presence of anemia or hypoxemia, the synthesis of EPO rapidly increases by more than 100 times and consequently increases the survival, proliferation and maturation of bone marrow progenitor cells also through the inhibition of apoptosis (programmed cell death).
Normal levels of EPO in the blood are about 2-25 mU / ml, but can increase 100-1000-fold in response to hypoxia.
The oxygen sensor mechanism leads to the interruption of EPO production when the number of red blood cells and / or the supply of oxygen to the tissues returns to equilibrium
The feedback mechanism ensures adequate production of RBCs to prevent anemia and tissue hypoxia, but not too high to lead to polycythemia with excessive blood viscosity and consequent cardiovascular risks.
The overproduction of EPO leading to polycythemia (secondary to be distinguished from polycythemia vera or primary: myeloproliferative disorder where EPO-independent clones of progenitor cells proliferate with an increase in both RBCs and granulocytes and platelets) can result from cardiac or respiratory diseases , from altitude, from obstructions of blood flow to the EPO production site, from EPO-producing tumors.
In secondary polycythemia, EPO levels are generally high, but they can also be normal due to an increase in its turnover.
It is known that the genetic differences existing between athletes can be an element at the basis of the different performance capacities.
Among the possible genetic differences, some may concern erythropoiesis in general and specifically erythropoietin.
One example is the story of the Finnish cross-country skier Eero Mäntyranta, double gold medalist at the 1964 Olympics in Innsbruck.
He was born with an Epo gene mutation (expressed at the receptor level) that increased his oxygen-carrying capacity with red blood cells by 25-50%.
This paraphysiological condition could be reproduced through gene manipulation.
The number of EPO receptors varies in the different cells of the erythrocyte line. The maximum occurs in the CFU-E, the number decreases as the differentiation and maturation of the erythrocyte cells progress. EPO.
EPO receptors have also been identified on myocytes, endothelial cells, the CNS, ovary and testes.
EPO, therefore, is thought to play a physiological role in heart and brain development.
EPO protects cardiac and nerve tissues from inflammation and ischemic damage: both through direct stimulation of nerve and heart cells and indirectly by mobilizing endothelial progenitor cells, thus promoting neo-vascularization.
) with respect to the physiological EPO, which however are reflected in the chemical and physical behavior of the molecule, for example there are differences in the electric charge.For ergogenic purposes, rHuEPO is used with injectable administrations every 2-3 days, for 3-4 weeks, associated with Iron preparations. In fact, in conditions of erythropoietin stimulation, it becomes necessary to have hemoglobin synthesized in athletes at a much higher rate than usual and this requires an adequate supply of iron to maintain erythropoietic efficiency. Half-life i.v. 8.5 hours.
Once the maintenance phase has been reached, the intake can take place at lower doses, which are more difficult to identify at doping controls.
Darbepoietin
More stable than EPO, with longer half-life (i.v. 25.3 hours) and greater efficacy; it is more easily identifiable due to its structural characteristics different from the endogenous human product and due to its lower clearance
Therapeutic uses of erythropoietin (epoetin; Eprex®, Globuren®, Neorecormon®; darbepoetin: Aranesp®, Nespo®)
- Anemia in chronic renal failure
- Zidovudine anemia (anti-HIV)
- "Refractory" anemia
- Anemia after anticancer chemotherapy
- Pathological deficiencies of EPO
- Myeloma
- Myelodysplastic syndromes.
Rapidly and continuously developing research on erythropoietin:
Products that mimic the activity of the EPO
Small peptides or non-peptide compounds that can bind, activating them, to the EPO receptors (Science 1996; 273: 458. Proc Natl Acad Sci USA 1999; 96: 12156)
Recently, for example, in in vitro experiments, silkworm hemolymph has been shown to inhibit the apoptosis of EPO-producing cells by increasing EPO production by 5 times (Biotechnol Bioeng 2005; 91: 793)
(hematocrit expressed as a percentage), hemoglobin levels, reticulocyte countIn cycling, hematocrit measurements above 50% lead to suspension. Values above 50% are suspected by the IOC
The International Ski Federation has imposed a hemoglobin limit of 18.5 g / dL in men and 16.5 g / dL in women, if found before a competition the athlete cannot participate to preserve his health.
It should be emphasized that hematocrit and hemoglobin values can vary from athlete to athlete and in response to the same exercise. The ideal is to have the hematological profile of each athlete over time:
the investigations to identify the use of EPO have extended to various sports and obviously to the Olympics
Marco Pantani was disqualified from the Tour of Italy for a hematocrit value of 52%
In 2003 the Kenyan middle distance runner Bernard Lagat (second best time ever in the 1500 m) tested positive (research of rHuEPO in the urine) for EPO intake before the World Athletics Championships in Paris (in which he could not participate) subsequent counter-analyzes, however, cleared him. This case demonstrated the need to seek more reliable tests.
Recently a new direct isoelectric method has been developed (with good results) to distinguish exogenous from endogenous EPO in urine samples, developed in the French laboratory of Chatenay-Malabry (Nature 2000; 405: 635; Anal Biochem 2002; 311: 119; Clin Chem 2003; 49: 901). It was possible to identify exogenous EPO even after 3 days from the intake
(Incidence 1-30%). The mechanism is not fully understood, "EPO has a" vasoconstrictive action and chronic exposure causes resistance to the vasodilating action of nitric oxide. Finally, EPO promotes the growth of smooth muscle cells of the vessels with vascular remodeling and hypertrophy which may contribute to the maintenance of hypertension [Am J Kidney Dis 1999; 33: 821-8]).
Bone pain (non-severe, transient, high incidence = 40%).
Convulsions (due to rapid increase in blood viscosity and hypoxic vasodilation loss with consequent increase in vascular resistance).
Headache.
Thromboembolic phenomena (PE, MI, stroke), all related to blood hyperviscosity.
Post-treatment anemia due to decreased endogenous EPO production.
Pure red cell aplasia (anti-EPO antibody formation?).
Myeloproliferative disorders (animal studies, long-term treatments?).
Damage from erythropoietin as doping
The data on the adverse reactions of erythropoietin listed above derive almost exclusively from therapeutic treatments in patients with underlying diseases
There are no studies on the harm of erythropoietin used as doping on healthy athletes
A study of athletes who were given EPO for 6 weeks found a significant increase in systolic blood pressure in response to sub-maximal exercise.
The number of deaths among Belgian and Dutch cyclists between 1987 and 1990 has been related to the use of EPO (Gambrell and Lombardo. Drugs and doping: blood doping and recombinant human erythropoietin. In: Mellion, M.B. (ed.): Sports medicine secrets. Philadelphia: Hanley & Belfus, 1994, pp. 130-3)
It is not wrong to think that the adverse reactions seen in patients can also occur in healthy athletes albeit with a lower incidence.
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