Serum Erythropoietin Concentration Research Articles

Accelerated destruction of erythrocytes in Tie2 promoter-driven STAT3 conditional knockout mice

AimsSTAT3 is a key modulator of activation and differentiation of macrophages. But it is still unknown if deficiency of STAT3 activates macrophages to destroy erythrocytes by phagocytosis. We generated STAT3 conditional knockout mice by crossing floxed STAT3 mice with Tie2 promoter-driven Cre-recombinase transgenic mice and clarified that Stat3 plays a critical role in the formation and activation of macrophages. Main methodsBlood cell count, reticulocyte count, serum lactate dehydrogenase, erythropoietin, iron and ferritin concentration, and life span of the erythrocytes in Tie2 promoter-driven STAT3 conditional knockout mice were analyzed. To explore the erythropoietic function of the mice, we subjected them to brief hemolytic anemia by injecting them intraperitoneally with phenylhydrazine. The fragility of erythrocytes was examined by scanning electron microscopy and osmotic tolerance test. Key findingsThe conditional knockout mice had mild normocytic anemia. They also displayed higher lactate dehydrogenase, ferritin and erythropoietin concentration, higher reticulocyte count, and a shorter lifespan of erythrocytes compared with wild-type controls. These data suggest that destruction of erythrocytes and secondary blood formation were accelerated in the STAT3 conditional knockout mice. It didn't appear due to the fragility of erythrocytes. A few of the conditional knockout mice suddenly developed acute severe anemia, high body temperature and massive splenomegaly, and died within 2weeks after the onset of anemia. SignificanceThis study provided evidence that STAT3 have a critical role in the destruction of erythrocytes by resident macrophages in the spleen.

Clinical and biochemical improvement following low‐dose intravenous iron therapy in a patient with erythropoietic protoporphyria

Clinical and biochemical improvement following low‐dose intravenous iron therapy in a patient with erythropoietic protoporphyria

EPO Modulation in a 14-Days Undersea Scuba Dive

Erythropoiesis is affected during deep saturation dives. The mechanism should be related to a downregulation of serum Erythropoietin (s-EPO) concentration or to a toxic effect of the hyperbaric hyperoxia. We evaluated s-EPO and other haematological parameters in 6 scuba divers before, during and after a 14-days guinness saturation dive (8-10 m). Athletes were breathing air at 1.8-2 ATA, under the control of a team of physicians. Serum parameters were measured before diving (T0) and: 7 days (T1), 14 days (T2) after the beginning of the dive and 2 h (T3) and 24 h (T4) after resurfacing. Hgb, and many other haematological parameters did not change whereas Ht, s-EPO, the ratio between s-EPO predicted and that observed and reticulocytes (absolute, percent) declined progressively from T0 to T3. At T4 a significant rise in s-EPO was observed. Hgb did not vary but erythropoiesis seemed to be affected as s-EPO and reticulocyte counts showed. All these changes were statistically significant. The experiment, conducted in realistic conditions of dive length, oxygen concentration and pressure, allows us to formulate some hypotheses about the role of prolonged hyperbarism on erythropoiesis. The s-EPO rise, 24 h after resurfacing, is clearly documented and related to the "Normobaric Oxygen Paradox". This evidence suggests interesting hypotheses for new clinical applications such as modulation of s-EPO production and Hgb content triggered by appropriate O₂ administration in pre-surgical patients or in some anemic disease.

The effects of vitamin C on DDP-induced anemia in rats

The aim of this study was to investigate the effects of vitamin C on cisplatin (DDP)-induced anemia and explore its possible mechanisms in rats. Adult male Sprague–Dawley rats were randomly divided into six groups: control, vitamin C 50, vitamin C 100, DDP, DDP plus vitamin C 50 and DDP plus vitamin C 100-treated groups. DDP was intravenous injected as a single dose and vitamin C was administered by gavage. Serum erythropoietin (Epo), hemoglobin (Hb) and blood urea nitrogen (BUN) concentration were measured 4 and 14 days after DDP treatment. The changes of renal tissue were examined by light microscope. Administration of DDP to rats induced anemia and nephrotoxicity, characterized with a significant decrease in serum Epo and Hb and increase in BUN concentrations. Pathological examination revealed that DDP caused significant renal damage in rats. Vitamin C administration produced amelioration in biochemical indices of anemia and nephrotoxicity and in histological change when compared to group DDP alone; concurrent administration of vitamin C at doses of 100 mg/kg being more effective. Results from this study indicate that the novel natural antioxidant vitamin C might have protective effect against DDP-induced anemia in rats.

Endothelial function does not relate to haemoglobin or serum erythropoietin concentrations and these do not explain the gender difference in endothelial function in healthy middle‐aged men and women

Haemoglobin scavenges nitric oxide, and a previous study has shown a negative association between flow-mediated vasodilation (FMD), a measure of nitric oxide (NO)-dependent vasomotor function and haemoglobin concentrations [Hb]. Circulating erythropoietin (EPO) is also negatively associated with [Hb] and could influence availability of NO. The purpose of this study was to examine the association of FMD with [Hb] and EPO concentrations and to determine whether these contribute to the sex difference in FMD. FMD (by high-resolution ultrasound), [Hb], circulating immunoreactive EPO and cardiovascular risk factors were measured in 317 healthy middle-aged men and women (183 women, 33 premenopausal, mean age ± SD, 55 ± 6·8 years) participating in a dietary study. In the whole mixed-sex group, FMD was negatively correlated with [Hb] (R = -0·23, P < 0·001). However, in a multivariable model, incorporating sex and other confounding factors, FMD was independently negatively correlated only with age, male sex and systolic blood pressure: standardized regression coefficients -0·21 (P < 0·01), -0·17 (P < 0·05) and -0·20 (P < 0·05) respectively and not with [Hb]. Similarly, when the analysis was restricted to men or to postmenopausal women, there was no significant relationship between FMD and Hb. There was no significant correlation between FMD and EPO on either univariate analysis in the whole group, in each sex, or in multivariate analysis. These results suggest that in healthy middle-aged subjects, FMD is not influenced by [Hb] or EPO and these do not contribute to the gender difference in FMD.

Efeito da idade e sexo sobre a concentração sérica de eritropoietina em equinos da raça Árabe

A EPO é um fator de crescimento glicoprotéico sintetizado pelas células adjacentes aos túbulos proximais renais regulada via mecanismo de "feed back" envolvendo a tensão de oxigênio tissular. Na baixa tensão de oxigênio arterial, a produção de EPO aumenta causando uma maior produção de eritrócitos na medula óssea. Devido ao pouco conhecimento da concentração de EPO sérica em equinos e a ausência de trabalhos sobre o efeito da idade e sexo sobre a sua concentração o trabalho teve como objetivo comparar a concentração sérica de eritropoietina em equinos da raça Árabe de sexos e idades diferentes. Foram utilizados 31 equinos da raça Árabe, com idades de seis a 12 meses (jovens) e acima de 24 meses (adultos), sendo 13 machos (seis jovens e sete adultos) e 18 fêmeas (oito jovens e 10 adultas), clinicamente sadios. As amostras de sangue foram colhidas por venipunção jugular e o soro armazenado até o momento do processamento. A concentração sérica de eritropoetina foi determinada pelo método de radioimunoensaio (RIA) utilizando kit comercial (EPO Trac TM125I RIA, Diagnostic Systems Laboratories, Webster, Texas, USA). Para análise estatística dos dados utilizou-se o Teste t de Student ao nível de 5% de significância (P&lt;0,05). Não foram observadas diferenças significativas (P&lt;0,05) quando se compararam os animais divididos entre sexos e as idades de seis a 12 meses (jovens) e acima de 24 meses (adultos). Conclui-se que a concentração de eritropoietina em equinos da raça Árabe independe do sexo e idade, e pode ser utilizada como valores de referência, porém ressalta-se a necessidade da obtenção de valores de referência para cada laboratório.

Increased Hemoglobin Mass and VO2max With 10 h Nightly Simulated Altitude at 3000 m

To quantify the changes of hemoglobin mass (Hbmass) and maximum oxygen consumption (VO2max) after 22 days training at 1300-1800 m combined with nightly exposure to 3000-m simulated altitude. We hypothesized that with simulated 3000-m altitude, an adequate beneficial dose could be as little as 10 h/24 h. Fourteen male collegiate runners were equally divided into 2 groups: altitude (ALT) and control (CON). Both groups spent 22 days at 1300-1800 m. ALT spent 10 h/night for 21 nights in simulated altitude (3000 m), and CON stayed at 1300 m. VO2max and Hbmass were measured twice before and once after the intervention. Blood was collected for assessment of percent reticulocytes (%retics), serum erythropoietin (EPO), ferritin, and soluble transferrin receptor (sTfR) concentrations. Compared with CON there was an almost certain increase in absolute VO2max (8.6%, 90% confidence interval 4.8-12.6%) and a likely increase in absolute Hbmass (3.5%; 0.9-6.2%) at postintervention. The %retics were at least very likely higher in ALT than in CON throughout the 21 nights, and sTfR was also very likely higher in the ALT group until day 17. EPO of ALT was likely higher than that of CON on days 1 and 5 at altitude, whereas serum ferritin was likely lower in ALT than CON for most of the intervention. Together the combination of the natural and simulated altitude was a sufficient total dose of hypoxia to increase both Hbmass and VO2max.

Potentiation of Hemostimulating Effects of Erythropoietin with Pegylated Hyaluronate-Endo-β-N-Acetylhexosaminidase

Pegylated hyaluronate-endo-β-N-acetylhexosaminidase considerably potentiates the hemostimulating effects of erythropoietin due to intensification of proliferation and differentiation of erythroid precursors against the background of enhanced secretion of hemopoietins by nonadherent hemopoiesis-inducing environment cells and elevation of serum erythropoietin concentration. The use of the enzyme allows 10-fold reduction of the maximum effective erythropoietin dose.

Aqueous erythropoietin level in retinal vein occlusion

AbstractPurpose To investigate the aqueous level of erythropoietin (EPO) and associated factors in patients with retinal vein occlusion (RVO).Methods The aqueous EPO level was measured prospectively with chemiluminescent immunoassay in consecutive patients with macular edema (ME) secondary to branched retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO). Aqueous fluid of cataract patients served as control. Patients taking anti‐hypertensive medication with angiotensin converting enzyme inhibitor or angiotensin II receptor blocker, prior intraocular surgery or injection of steroid or antiangiogenic factors, or longstanding (3&gt; months) BRVO or CRVO were excluded. We also evaluated whether aqueous EPO was associated with factors such as serum EPO concentration, non‐perfusion area, and arterio‐venous (AV) transit time, and central macular thickness (CMT).Results Aqueous level of EPO was higher in RVO (27 eyes; BRVO 16 eyes/CRVO 11 eyes) than in control subjects (RVO, 68.1 [19.8‐190] mU/ml vs. control, 12.9 [5.4‐24.4] mU/ml, P&lt;0.001). More specifically, aqueous EPO was higher in CRVO than in BRVO (CRVO, 118.9 [31.8‐190] mU/ml vs. 33.3 [19.8‐62.5] mU/ml, P&lt;0.001). However, no differences were found in serum levels of EPO among controls, BRVO, and CRVO groups (CRVO, 11.1mU/ml[5.4‐16.4] vs. BRVO, 10.0mU/ml[6.7‐16] vs. control, 9.2mU/ml[5.7‐11.2], P=0.091). CMT in RVO patients had positive correlation with the aqueous level of EPO in RVO (P=0.003). Also, in terms of non‐perfusion area, there was a significant difference in the aqueous level of EPO between ischemic and non‐ischemic subtypes of CRVO (ischemic, 172 [156‐190] mU/ml vs. non‐ischemic, 83.6 [56.3‐142.5] mU/ml, P=0.0027).Conclusion In RVO, aqueous levels of EPO are elevated and could be associated with retinal ischemia and ME

Hemolysis induced by an extreme mountain ultra‐marathon is not associated with a decrease in total red blood cell volume

Prolonged running is known to induce hemolysis. It has been suggested that hemolysis may lead to a significant loss of red blood cells; however, its actual impact on the erythrocyte pool is unknown. Here, we test the hypothesis that prolonged running with high hemolytic potential decreases total red blood cell volume (RCV). Hemolysis (n = 22) and RCV (n = 19) were quantified in ultra-marathon runners before and after a 166-km long mountain ultra-endurance marathon (RUN) with 9500 m of altitude gain/loss. Assessment of total hemoglobin mass (Hbmass) and RCV was performed using a carbon monoxide rebreathing technique. RUN induced a marked acute-phase response and promoted hemolysis, as shown by a decrease in serum haptoglobin (P < 0.05). Elevated serum erythropoietin concentration and reticulocyte count after RUN were indicative of erythropoietic stimulation. Following RUN, runners experienced hemodilution, mediated by a large plasma volume expansion and associated with a large increase in plasma aldosterone. However, neither Hbmass nor RCV were found to be altered after RUN. Our findings indicate that mechanical/physiological stress associated with RUN promotes hemolysis but this has no impact on total erythrocyte volume. We therefore suggest that exercise 'anemia' is entirely due to plasma volume expansion and not to a concomitant decrease in RCV.

Neopterin, inflammation-associated product, prolongs erythropoiesis suppression in aged SAMP1 mice due to senescent stromal-cell impairment

Anemia induced by inflammation is well known to be more serious in the elderly than in non-elderly adults; however, the reason why this is so remains unclear. Neopterin produced by monocytes during inflammation promotes myelopoiesis but suppresses B-lymphopoiesis and erythropoiesis, by activating stromal cells in mice. Here, age-related changes in the erythropoietic response to neopterin were determined using senescence accelerated mice (SAMP1) with senescence stromal-cell impairment. Intravenous injection of neopterin into young mice (8-12 weeks old) resulted in a decrease in erythroid progenitor cell number in the bone marrow (BM), concomitant with an increase in myeloid progenitor cell number over one week. Intravenous injection of neopterin into aged mice (30-36 weeks old) resulted in a prolonged decrease in erythroid progenitor cell number in the BM over three weeks and a limited increase in myeloid progenitor cell number over one day. Neopterin treatment induced a decrease in serum erythropoietin concentrations in young mice but not in aged mice. The gene expression of tumor necrosis factor α (TNF-α), a negative regulator of erythropoiesis, was up-regulated in the BM of both young and aged mice, and the degree of TNF-α up-regulation was the same in both groups. The gene expression of interleukin (IL)-11, a positive regulator of erythropoiesis, was also up-regulated over one day in both young and aged mice. However, IL-11 gene expression remained up-regulated thereafter in young mice, whereas it was rapidly down-regulated in aged mice. These data suggest that prolonged suppression of erythropoiesis in aged mice may be due to a decrease in the production of positive regulators rather than to an increase in the production of negative regulators. Our combined data suggest that age-related impairment of stromal cells induces serious anemia in the elderly during inflammation.

Hepcidin is correlated to soluble hemojuvelin but not to increased GDF15 during pregnancy

Increased maternal and foetal iron requirements during pregnancy are compensated by an increase of intestinal iron absorption. Animal studies have shown that the expression of the main iron regulator hepcidin is significantly suppressed during pregnancy, but the factors associated with hepcidin suppression remain unknown. To investigate possible suppressors of hepcidin expression during pregnancy we determined serum concentrations of growth-differentiation factor-15 (GDF15), erythropoietin (EPO), soluble hemojuvelin (HJV) and hepcidin in 42 pregnant women at different time points of gestation and correlated them with serum iron and haematological parameters. Serum iron parameters and serum hepcidin concentration significantly decreased during pregnancy, whereas serum concentrations of GDF15, EPO and soluble HJV significantly increased. A negative correlation of hepcidin with EPO and soluble HJV but no correlation between hepcidin and GDF15 was found. Hepcidin and ferritin were positively correlated throughout the pregnancy. Our findings suggest that hepcidin expression is controlled by body iron stores where soluble HJV and EPO may act as suppressors of hepcidin.

Erythropoietin, ferritin, haptoglobin, hemoglobin and transferrin receptor in metabolic syndrome: a case control study

BackgroundIncreased ferritin concentrations are associated with metabolic syndrome (MetS). The association between ferritin as well as hemoglobin level and individual MetS components is unclear. Erythropoietin levels in subjects with MetS have not been determined previously. The aim of this study was to compare serum erythropoietin, ferritin, haptoglobin, hemoglobin, and transferrin receptor (sTFR) levels between subjects with and without MetS and subjects with individual MetS components.MethodsA population based cross-sectional study of 766 Caucasian, middle-aged subjects (341 men and 425 women) from five age groups born in Pieksämäki, Finland who were invited to a health check-up in 2004 with no exclusion criteria. Laboratory analyzes of blood samples collected in 2004 were done during year 2010. MetS was defined by National Cholesterol Education Program criteria.Results159 (53%) men and 170 (40%) women of study population met MetS criteria. Hemoglobin and ferritin levels as well as erythropoietin and haptoglobin levels were higher in subjects with MetS (p < 0.001, p = 0.018). sTFR level did not differ significantly between subjects with or without MetS. Hemoglobin level was significantly higher in subjects with any of the MetS components (p < 0.001, p = 0.002). Ferritin level was significantly higher in subjects with abdominal obesity or high TG or elevated glucose or low high density cholesterol component (p < 0.001, p = 0.002, p = 0.02). Erythropoietin level was significantly higher in subjects with abdominal obesity component (p = 0.015) but did not differ significantly between subjects with or without other MetS components. Haptoglobin level was significantly higher in subjects with blood pressure or elevated glucose component o MetS (p = 0.028, p = 0.025).ConclusionSubjects with MetS have elevated hemoglobin, ferritin, erythropoietin and haptoglobin concentrations. Higher hemoglobin levels are related to all components of MetS. Higher ferritin levels associate with TG, abdominal obesity, elevated glucose or low high density cholesterol. Haptoglobin levels associate with blood pressure or elevated glucose. However, erythropoietin levels are related only with abdominal obesity. Higher serum erythropoietin concentrations may suggest underlying adipose tissue hypoxemia in MetS.

The Bone Marrow Hematopoietic Microenvironment Is Functionally Impaired in Iron-Overloaded Mice,

Abstract 3173 Background and Purpose:Deferasirox (DFX) is an oral iron chelator that enables effective chelation by once daily administration.Since the introduction of DFX, iron chelation therapy (ICT) for transfusional iron overload has attracted increased attention. It is known that excess iron increases oxidative stress and affects various organs, such as the liver, heart and endocrine glands, negatively. Sufficient ICT can remove excess iron and improve organ dysfunction in iron-overloaded patients, and accumulating data has indicated that efficient ICT improves the survival of transfusion-dependent patients with myelodysplastic syndromes (MDS). Recently, we experienced a case of MDS with transfusional iron overload in which the hematopoietic data improved unexpectedly after administration of DFX without any other specific treatments (Okabe H et al. Rinsho Ketsueki, 2009). An increasing number of similar cases has been reported. This clinical observation indicates that iron overload could also affect the hematopoietic system unfavorably, via, as yet, unknown mechanisms. Methods and Results:We generated iron-overloaded mice to investigate how iron overload affects hematopoiesis in vivo. C57BL6 mice were injected with a total of 200 mg of iron dextran, intraperitoneally over 4 weeks. The iron-overloaded mice showed pigmented skin and hepatosplenomegaly, and histological examination showed excess iron deposition in the bone marrow, liver, spleen and heart. The serum and organ iron concentrations in these mice markedly increased. However, the iron-overloaded mice did not show any significant changes in peripheral blood counts or the proportion of immature hematopoietic cells in the bone marrow. To further examine the effects of excess iron on the biological functions of hematopoietic stem and progenitor cells (HSPCs), we performed bone marrow transplantation (BMT) assays. First, to assess the hematopoietic reconstitutional capacity of the HSPCs of iron-overloaded mice, we transplanted bone marrow cells (1×106 cells) from iron-overloaded mice or normal mice into lethally irradiated normal recipient mice along with the same number of normal competitor cells. We found no significant difference in hematopoietic reconstitution between the iron-overloaded donor cells and the normal donor cells, suggesting that the hematopoietic reconstitutional capacity of HSPCs in iron-overloaded mice is not significantly affected by iron. In contrast, when we transplanted bone marrow cells from normal mice (2×106 cells) into iron-overloaded recipients, hematopoietic recovery was significantly delayed, in particular platelet counts (at 2 weeks after BMT, normal recipients vs. iron-overloaded recipients, 63.4±9.4 vs. 18.7±4.7×104/μl, respectively, p<0.001). This indicates that excess iron disturbs the function of the bone marrow microenvironment and delays hematopoietic reconstitution. Microarray and quantitative RT-PCR analysis of non-hematopoietic bone marrow cells (CD45-/Ter119-) from the iron-overloaded mice demonstrated significant reductions in CXCL12, VCAM-1, Kit-ligand and IGF-1, which are important regulators of hematopoiesis. In addition, in the iron-overloaded mice, the serum concentration of erythropoietin and the expression level of thrombopoietin in the liver were also significantly reduced. Furthermore, increased oxidative stress levels were observed in the iron-overloaded liver and bone marrow. Conclusion:We did not observe any direct effects of excessive iron on hematopoietic cells, but found significant impairment of the hematopoietic microenvironment in the bone marrow of iron-overloaded mice. These results suggest that oxidative stress induced by excess iron could disturb the hematopoiesis-supporting capacity of the bone marrow microenvironment by reducing the expression of many essential molecules. Disclosures:No relevant conflicts of interest to declare.

Chuvash polycythemia VHLR200W mutation is associated with down-regulation of hepcidin expression

AbstractHypoxia is known to reduce the expression of hepcidin, the master regulator of iron metabolism. However, it is not clear whether this response is primarily related to increased erythropoiesis driven by hypoxically stimulated erythropoietin or to a more direct effect of hypoxia on hepcidin expression. The germline loss-of-function VHLR200W mutation is common in Chuvashia, Russia, and also occurs elsewhere. VHLR200W homozygotes have elevated hypoxia-inducible factor 1α (HIF-1α) and HIF-2α levels, increased red cell mass, propensity to thrombosis, and early mortality. Ninety VHLR200W homozygotes and 52 controls with normal VHL alleles from Chuvashia, Russia, were studied under basal circumstances. In univariate analyses, serum hepcidin concentration was correlated positively with serum ferritin concentration and negatively with homozygosity for VHLR200W. After adjustment for serum erythropoietin and ferritin concentrations by multiple linear regression, the geometric mean (95% confidence interval of mean) hepcidin concentration was 8.1 (6.3-10.5) ng/mL in VHLR200W homozygotes versus 26.9 (18.6-38.0) ng/mL in controls (P < .001). In contrast, a significant independent relationship of serum erythropoietin, hemoglobin, or RBC count with hepcidin was not observed. In conclusion, up-regulation of the hypoxic response leads to decreased expression of hepcidin that may be independent of increased erythropoietin levels and increased RBC counts.

Effects of sildenafil citrate on five dogs with Eisenmenger’s syndrome

To determine the effect of sildenafil for dogs with Eisenmeger's syndrome and secondary erythrocytosis. This is a prospective, single arm, open-label study. Five clinical dogs with Eisenmeger's syndrome and secondary erythrocytosis were included. New York Heart Association functional class, packed cell volume, pulmonary artery acceleration time to ejection time ratio and serum erythropoietin concentration were evaluated before and after sildenafil therapy (0·5 mg/kg, twice a day). New York Heart Association functional class was significantly improved after one (median 2; range 1 to 2, P=0·031) and three months (median 2; range 1 to 2, P=0·031) of sildenafil therapy, compared with the baseline (median 3, range 2 to 3). Packed cell volume was significantly decreased after three months (median 59%; range 56 to 63, P=0·031) of therapy, compared with the baseline (median 71%; range 58 to 74). Acceleration time to ejection time ratio had increased and serum erythropoietin concentration had decreased particularly after 1 month of therapy, but there was no statistical significance. Sildenafil improved the clinical signs and secondary erythrocytosis in dogs with Eisenmeger's syndrome. Sildenafil therapy could be a useful treatment for dogs with Eisenmeger's syndrome.

Erythropoietin levels in endocrinopathies

Erythropoietin (EPO) is an oxygenregulated hormone promoting the differentiation of erythroid progenitor cells. Apart fromhypoxia, few data is available about release by secretagogues including hormones. To investigate EPO serum concentration in subjects with endocrine diseases. A retrospective study evaluating serumEPO concentrations in serumleftovers fromsubjects with various endocrine disorders. EPO is not noticeably influenced by thyroid hormone or cortisol concentrations and the relationship with hemoglobin concentration is preserved. In acromegalic patients, the latter is lost but EPO is neither statistically influenced by GH/IGF-I. This may reflect a dual action of GH and/or IGF-I on erythroid progenitors proliferation as well as on EPO synthesis. EPO is not noticeably modified by endocrine disorders although GH and or IGF-I may alter EPO relationship with blood hemoglobin concentration.

Exercise training restores the endothelial response to vascular growth factors in patients with stable coronary artery disease

Exercise training partially corrects endothelial dysfunction in patients with coronary artery disease (CAD). Growth factors like vascular endothelial growth factor (VEGF) as well as erythropoietin (EPO) are known to modulate the bioavailability of nitric oxide and, thereby, contribute to the maintenance of a normal vascular tone. The aim of the present study was to determine the impact of 4 weeks of exercise training on circulating growth factors and to elucidate their involvement in the training-induced changes in vasomotion in patients with CAD. A total of 39 patients were enrolled (training group: n = 20; control group: n = 19). At start of study and after 4 weeks, average peak flow velocity (APV) of the left internal mammary artery (LIMA) in response to acetylcholine was measured invasively in the treatment and control groups. Serum concentrations of VEGF and EPO were determined by enzyme-linked immunosorbent assay. After exercise training, LIMA APV in response to acetylcholine was increased by 93% (from 69 ± 17% at start of study to 133 ± 16% at 4 weeks, p < 0.01 vs. start of study and control). At start of study, there was no association between any of the vascular growth factors and endothelial function. However, after exercise training a close correlation was apparent between the acetylcholine-induced change in APV and EPO (r = 0.69, p < 0.01) and VEGF (r = 0.76, p < 0.01) serum concentrations. In the control group, these correlations were not evident and there was no change in endothelial function either. Exercise training improves agonist-mediated endothelium-dependent vasodilatation in CAD, partially through a restoration of the endothelial response to EPO and VEGF.

Polycythemia and Inappropriate Erythropoietin Concentrations in Two Dogs with Renal T-cell Lymphoma

Two dogs presented with suspected renal disease and polycythemia. Abdominal ultrasound examinations performed on both dogs revealed coalescing masses causing bilateral renomegaly. Serum erythropoietin (EPO) concentrations were physiologically inappropriate. Postmortem examinations revealed renal T-cell lymphoma in both dogs. One of the two dogs also had involvement of the liver and mesentery. EPO-immunohistochemistry on tissue samples demonstrated positive staining in tumor cells and occasional normal renal cells. This report illustrates that paraneoplastic EPO production may induce polycythemia. The pattern of EPO-immunohistochemistry staining suggested that the mechanism of production was due to tumor production of EPO and local hypoxia-induced EPO production from compression of normal renal cells and vasculature.

Effects of high altitude training on exercise capacity: fact or myth

High altitude training has become a mainstay in endurance sports, with live high-train low as the current protocol of choice. Athletes either live or sleep in artificial or natural hypoxic conditions with the aim to increase serum erythropoietin concentrations, which are thought to improve maximum oxygen uptake and thus exercise performance. Changes, however, are not very striking and only apparent in so-called responders, who are not a well-defined group and may be as little as 50% of the trained study population. Whereas some studies show minor improvement, others report no change or even worsening. Furthermore, the mechanisms behind the proposed beneficial changes remain obscure and are far from being proven. There is an evident lack of sufficiently powered randomized, double-blinded studies, with training protocols that are identical for all groups and groups that are indeed comparable. Several studies discriminate between responders and non-responders, without clearly assessing the characteristics of the so-called responders. Until this has been done, it remains unclear if such a group really exists and how these subjects are characterized. This, however, would be of immense value, so protocols could be tailored to athletes' needs. Taken together, the current literature on natural or artificial hypoxia somewhat documents improved performance at high but not low altitude.