Cost benefits of low dose subcutaneous erythropoietin in patients with anaemia of end stage renal disease.

OBJECTIVE--To assess the cost benefits of low dose subcutaneous recombinant human erythropoietin in correcting the anaemia of end stage renal disease. DESIGN--Three year retrospective study. SETTING--Subregional nephrology service serving a mixed urban and rural population of 800,000. SUBJECTS--60 patients with symptoms of anaemic end stage renal disease treated with erythropoietin (43 receiving haemodialysis; 11 receiving continuous ambulatory peritoneal dialysis; two with predialysis end stage renal disease; four with failing renal transplants). MAIN OUTCOME MEASURES--Costs and savings of achieving and maintaining a haemoglobin concentration of 85-105 g/l with erythropoietin. RESULTS--All patients treated with erythropoietin achieved the target haemoglobin concentration at median induction doses of 97 (95% confidence interval 95 to 108) units/kg/week, and this was maintained with 79 (75 to 95) units/kg/week at an average annual cost per patient of 2260 pounds. Admissions related to anaemia were virtually eliminated (246 v 1 inpatient days for 12 months before and after starting erythropoietin). 54 patients required no blood transfusions after starting erythropoietin, and the total requirements fell from 230 to 21 units in the 12 months before and after starting erythropoietin. Iron stores were maintained with oral or intravenous iron. All patients reported increased wellbeing, appetite, and exercise capacity. Hypertension developed or worsened in 30 patients, resulting in hospital admissions in five patients, one of whom had seizures. CONCLUSION--Low dose subcutaneous erythropoietin restores haemoglobin concentrations sufficiently to abolish blood transfusion requirements and reduce morbidity. The net cost of erythropoietin prescribed in this way (2260 pounds/patient/year) was largely offset by savings in costs of hospital admissions. The true annual cost to the NHS was around 1200 pounds per patient.     

Association between recombinant human erythropoietin and quality of life and exercise capacity of patients receiving haemodialysis. Canadian Erythropoietin Study Group.

OBJECTIVE--To determine whether recombinant human erythropoietin improves the quality of life and exercise capacity of anaemic patients receiving haemodialysis. DESIGN--A double blind, randomised, placebo controlled study. SETTING--Eight Canadian university haemodialysis centres. PATIENTS--118 Patients receiving haemodialysis aged 18-75 with haemoglobin concentrations less than 90 g/l, no causes of anaemia other than erythropoietin deficiency, and no other serious diseases. INTERVENTIONS--Patients were randomised to three groups to receive placebo (n = 40), erythropoietin to achieve a haemoglobin concentration of 95-110 g/l (n = 40), or erythropoietin to achieve a haemoglobin concentration of 115-130 g/l (n = 38). Erythropoietin was given intravenously thrice weekly, initially at 100 units/kg/dose. The dose was subsequently adjusted to achieve the target haemoglobin concentration. All patients with a serum ferritin concentration less than 250 micrograms/l received oral or intravenous iron for one month before the study and as necessary throughout the trial. MAIN OUTCOME MEASURES--Scores obtained with kidney disease questionnaire, sickness impact profile, and time trade off technique; and results of six minute walk test and modified Naughton stress test. RESULTS--The mean (SD) haemoglobin concentration at six months was 74 (12) g/l in patients given placebo, 102 (10) g/l in those in the low erythropoietin group, and 117 (17) g/l in those in the high erythropoietin group. Compared with the placebo group, patients treated with erythropoietin had a significant improvement in their scores for fatigue, physical symptoms, relationships, and depression on the kidney disease questionnaire and in the global and physical scores on the sickness impact profile. The distance walked in the stress test increased in the group treated with erythropoietin, but there was no improvement in the six minute walk test, psychosocial scores on the sickness impact profile, or time trade off scores. There was no significant difference in the improvement in quality of life or exercise capacity between the two groups taking erythropoietin. Patients taking erythropoietin had a significantly increased diastolic blood pressure despite an increase in either the dose or number of antihypertensive drugs used. Eleven of 78 patients treated with erythropoietin had their sites of access clotted compared with only one of 40 patients given placebo. CONCLUSIONS--Patients receiving erythropoietin were appreciably less fatigued, complained of less severe physical symptoms, and had moderate improvements in exercise tolerance and depression compared with patients not receiving erythropoietin. At the doses used in this trial there was a higher incidence of hypertension and clotting of the vascular access in patients treated with erythropoietin.     

Single dose recombinant human erythropoietin reduces transforming growth factor beta in patients on chronic haemodialysis.

Short-term effects of recombinant human erythropoietin on serum levels of transforming growth factor beta-1, interleukin 1-alpha, interleukin 3, interferon gamma, and tumour necrosis factor alpha in patients with chronic renal failure on chronic haemodialysis were investigated. Recombinant human erythropoietin was applied subcutaneously in a dose of 75 IU/kg on 19 patients. Serum levels of transforming growth factor beta-1, interleukin 1-alpha, interleukin 3, interferon gamma, tumour necrosis factor alpha and erythropoietin, red blood cell parameters: red blood cell count, haemoglobin, haematocrit, and erythrocyte indices were determined before and after recombinant human erythropoietin single application. Transforming growth factor beta-1 serum levels were decreased after recombinant human erythropoietin (22.70 +/- 1.51 ng/ml versus 18.77 +/- 1.70 ng/ml (p < 0.01). None of the other investigated parameters was influenced significantly by recombinant human erythropoietin. Recombinant human erythropoietin in patients with chronic renal failure on chronic haemodialysis may influence anaemia not only through its stimulating effect on erythropoiesis, but also by direct oxygen-independent decrease of at least one of the negative regulators of erythropoiesis--the transforming growth factor beta.     

Treatment of anemia in patients with renal failure using erythropoietin obtained by genetic recombination

In 5 haemodialyzed patients with end-stage renal failure an effect of human recombinant erythropoietin (r-huEpo) on haemoglobin, haematocrit and iron metabolism was studied. After 12 weeks of the treatment, a significant increase in haemoglobin and haematocrit but significant decrease in plasma ferritin were noted. During r-huEpo treatment, one patients presented clinical symptoms of increased blood coagulation whereas another patients an increase in blood pressure. r-huEpo did not influence leukocytes and platelets count as well as liver function tests. Our results suggest, that r-huEpo is highly effective and safe in the treatment of anaemia in patients with chronic uraemia. Iron metabolism, blood pressure and blood coagulation must be monitored during therapy with r-huEpo.     

Clinical use of rHuEPO in bone marrow transplantation

Recipients of bone marrow (BMT) or peripheral blood progenitor stem cells (PBSCT) transplant have in the period following transplantation a frequent need for red blood cell transfusions and therefore an increased risk of blood-transmitted infections. The anaemia is caused mainly by myelosuppression after high-dose chemotherapy, but an impaired erythropoietin (EPO) production and an inappropriate EPO response may also contribute. Since recombinant human erythropoietin (rHuEPO) has been established as a treatment for renal anaemia it has been of interest whether treatment may be of benefit in the transplant setting. This paper gives an overview of the studies conducted to date with rHuEPO treatment in patients receiving bone marrow transplants. Current data donot support any transfusional benefits when rHuEPO is used in patients receiving autologous transplants. However, in patients receiving allogeneic transplants several studies clearly indicate a therapeutic role for rHuEPO with patients showing accelerated erythroid engraftment, increased haemoglobin levels, a reduced requirement for red blood cell transfusions, and a shortened time to transfusion independence. Especially patients with immune haemolysis after transplantation seems to benefit from the treatment. In addition, rHuEPO treatment has been used for lateonset anaemia after BMT and to prevent the need for homologous red blood cell transfusions to the BMT donor. To reduce costs, it is important in future studies to identify not only the optimal dose and route of administration of rHuEPO but also the most effective combination with other haematopoietic growth factors and cytokines that are used before and after transplantation.     

Improvement of anaemia in haemodialysed patients after viral or toxic hepatic cytolysis.

Thirty patients receiving haemodialysis, including two who had undergone bilateral nephrectomy, showed significant increases (p less than 0.001) in packed cell volume, haemoglobin concentration, and reticulocyte count during an episode of viral or toxic liver cytolysis. In 19 cases the episode lasted a mean of 5.0 +/- SD 2.9 months and was accompanied by improved haematological values for a mean of 12.0 +/- 6.0 weeks. Of the remaining patients, in whom the episode lasted a mean of 8.0 +/- 3.5 months (p less than 0.02), seven showed continued improvement a mean of 30.0 +/- 16.0 weeks after cytolysis. In eight patients in this group there was an apparent correlation between persistently increased haemoglobin concentrations and biopsy evidence of chronic hepatitis. The findings suggest that the reduction in anaemia resulted from enhanced red-cell production mediated by secretion of erythropoietin from regenerating liver cells. If confirmed this might have important implications for the treatment of anaemia in chronic renal insufficiency.     

Red blood cells

Red blood cells are derived from haemopoietic stem cells in bone marrow. Following a series of maturation steps, directed largely by the hormone erythropoietin (Epo), red cells enucleate and enter the circulatory system. In circulation these small, flexible biconcave cells containing haemoglobin transport O₂ from the lungs to the periphery, and CO₂ back from the periphery to the lungs. The most common disorders associated with red blood cells are anaemias. While there are numerous causes of anaemia, the reduced capacity for gaseous exchange is the underlying theme. Over the past 15 years, recombinant Epo has been used extremely successfully in the treatment of several forms of anaemia. The single gene disorders collectively known as haemoglobinopathies represent one of the best opportunities for gene therapy.     

Inadequate erythropoietin production (epo) in patients with multiple myeloma

Anaemia is the most common haematological complication in patients with malignant diseases. It is found in 60%-90% of cases with multiple myeloma. The pathogenesis of this hypoproliferative, normochromic, normocytic anaemia is complex. Results from clinical studies which evaluate the efficacy of recombinant human erythropoietin (rHuEpo) refer to the possibility that patients with multiple myeloma independently of renal function could have Epo deficiency. Based on this finding, the aim of the study was to evaluate the erythropoietin production in patients with multiple myeloma in order to define clinical conditions of Epo deficiency and thereby enable rational use of this expensive drug. 42 patients with multiple myeloma were examined. The control group consisted of 25 patients with iron deficiency anaemia. 14 healthy volunteers represented the so-called "normal" control. The adequacy of Epo production was estimated from the graphic representation of the linear regression between Epo and haemoglobin (Hb) in the control group, as well as from O/PEpo ratio as a measure of the degree of adequacy of Epo production (O -- observed Epo value, P -- predicted Epo value from the regression equation of the control group). The erythropoietic activity was estimated from the graphic representation of the linear regression between soluble transferin receptors (sTfR) and Hb in the control group, as well as from O/PsTfR ratio, as a measure of the degree of adequacy of erythropoietic activity (O -- observed sTfR value, P -- predicted sTfR value from the regression equation of the control group). Significant inverse correlation between Epo and Hb was found in patients with multiple myeloma but preserved renal function, which was not the case in patients with renal insufficiency. 43% of patients without renal insufficiency and 85% of patients with renal insufficiency had inadequate Epo response to anaemia. In both patient groups (with and without renal insufficiency) instead of the expected inverse relationship between Hb and sTfR as in the control group, a positive correlation was found. 76% of patients had inadequate sTfR response to anaemia. There is a positive correlation between O/PEpo and O/PsTfR which is in favour of Epo driven erythropoiesis. O/PEpo and O/PsTfR in patients with multiple myeloma are significantly lower in comparison to the control group, which also points to the inadequacy of erythropoietin production, respectively erythropoietic activity. In conclusion, the results from this study show unambiguously that anaemia in patients with multiple myeloma appears because of decreased erythropoiesis as a consequence of bone marrow infiltration with malignant plasma cells as well as inadequate Epo production. Most probably, there are two forms of inadequate Epo production: one because of the renal insufficiency and the other that found in patients with anaemia of chronic diseases the mechanism of which is not clear.     

Effect of recombinant human erythropoietin on anterior pituitary function in patients on chronic hemodialysis.

In 7 patients with end stage renal failure, anterior pituitary function was tested by simultaneous application of maximally effective doses of the hypothalamic releasing peptides, corticotropin-releasing hormone, growth hormone-releasing hormone, thyrotropin-releasing hormone and gonadotropin-releasing hormone, and compared to 8 normal controls. In addition to the pituitary hormones, plasma cortisol, thyroxine and testosterone concentrations were measured. To test for possible effects of treatment with recombinant human erythropoietin (rhu-EPO), all patients with chronic renal failure were studied again after partial correction of anemia by treatment with erythropoietin. Before initiation of rhu-EPO treatment, plasma concentrations of follicle-stimulating hormone were significantly elevated and the thyroid-stimulating hormone and prolactin responses to thyrotropin-releasing hormone blunted when compared to normal controls. Treatment with rhu-EPO induced a significant increase in plasma ACTH and follicle-stimulating hormone concentrations. All other pituitary functions remained unchanged. Thus, the general improvement in well-being, working capacity and sexual activity cannot be attributed to hormonal changes.     

Beta2-microglobulin causes abnormal phosphatidylserine exposure in human red blood cells

The exposure of the aminophospholipid phosphatidylserine on the external leaflet of red blood cell plasma membrane can have several pathophysiological consequences with particular regard to the processes of cell phagocytosis, haemostasis and cell-cell interaction. A significant increase in phosphatidylserine-exposing erythrocytes has been reported in chronic haemodialysis patients and found to be strongly influenced by the uraemic milieu. To identify uraemic compound(s) enhancing phosphatidylserine externalization in erythrocytes, we fractionated by chromatographic methods the ultrafiltrate obtained during dialysis, and examined by flow cytometry the effect of the resulting fractions on phosphatidylserine exposure in human red cells. Chromatographic procedures disclosed a homogeneous fraction able to increase erythrocyte phosphatidylserine exposure. The inducer of such externalization was identified by monodimensional gel electrophoresis and mass spectrometry investigations as beta2-microglobulin. To confirm the beta2-microglobulin effect and to examine the influence of protein glycation (as it occurs in uraemia) on phosphatidylserine erythrocyte exposure, erythrocytes from normal subjects were incubated with recombinant beta2-microglobulin (showing no glycation sites at mass analysis), commercial beta2-microglobulin (8 glycation sites), or with in vitro glycated recombinant beta2-microglobulin (showing multiple glycation sites). Elevated concentrations of beta2-microglobulin (corresponding to plasma levels reached in dialysis patients) increased slightly but significantly the protein's ability to externalize phosphatidylserine on human erythrocytes. Such an effect was markedly enhanced by glycated forms of the protein. Beta2-microglobulin is recognized as a surrogate marker of middle-molecule uraemic toxins and represents a key component of dialysis-associated amyloidosis. Our study adds further evidence to the potential pathophysiologic consequences of beta2-microglobulin accumulation in chronic uraemic patients.     

Red cell ferritin content: a re-evaluation of indices for iron deficiency in the anaemia of rheumatoid arthritis.

In iron deficiency anaemia basic red cell content of ferritin is appreciably reduced. This variable was determined in 62 patients with rheumatoid arthritis to evaluate conventional laboratory indices for iron deficiency in the anaemia of rheumatoid arthritis. For 23 patients with rheumatoid arthritis and normocytic anaemia irrespective of plasma ferritin concentration, red cell ferritin content did not differ significantly from that for non-anaemic patients with rheumatoid arthritis. For 27 patients with rheumatoid arthritis and microcytic anaemia, the mean red cell ferritin content for patients with a plasma ferritin concentration in the 13-110 micrograms/l range was appreciably reduced. It was indistinguishable from that for patients with rheumatoid arthritis and classical iron deficiency anaemia, indicated by plasma ferritin concentrations of less than 12 micrograms/l. In contrast, the mean red cell ferritin content for patients with rheumatoid arthritis, microcytic anaemia, and plasma ferritin concentrations above 110 micrograms/l did not differ from that for patients with rheumatoid arthritis and normocytic anaemia. Oral treatment with iron in patients with rheumatoid arthritis, microcytic anaemia, and appreciably reduced red cell ferritin concentrations was accompanied by significant increases in haemoglobin concentration (p less than 0.01), mean corpuscular volume (p less than 0.01), and red cell ferritin contents (p less than 0.05). This treatment, however, did not produce any appreciable change in haemoglobin concentration in patients with rheumatoid arthritis, normocytic anaemia, and normal red cell ferritin contents. These findings suggest that the indices for iron deficiency in patients with rheumatoid arthritis and anaemia should include peripheral blood microcytosis together with a plasma ferritin concentration of less than 110 micrograms/l.     

Decrease of erythropoietin level by human recombinant tumour necrosis factor alpha (hrec TNFalpha) in patients with advanced cancer

Anaemia is a frequent complication of chronic inflammation, infectious diseases and cancer. Inappropriate erythropoietin production is regarded as one of the main causative factors responsible for the occurrence of anaemia. The pathogenesis of TNFalpha induced-anaemia has not been fully clarified yet and its influence on hematopoiesis has been suggested. We performed a clinical study to access the influence of hrec TNFalpha administration on plasma EPO concentration and the degree of anaemia in patients with advanced solid tumours for whom no other kind of therapy but palliative treatment was available. All these patients exposed mild anaemia (HT 36.1 +/- 1.0%). Plasma EPO was estimated at 8 a.m. before and after 5 days of TNFalpha therapy with a dose of 75 pg/day iv (cycle I). Two weeks later plasma EPO was estimated again before and after 5 days of TNFalpha administration of a double dose (150 microg/day) (cycle II). The control group comprised 8 non-cancer patients (5M/3F, age 48.5 +/- 6yr) with the same degree of anaemia (HT 36 +/- 1.1%) due to haemorrhage. In the control group the plasma EPO level was significantly higher (54.2 +/- 8 mU/ml) than in cancer patients before cycle I (17.1 +/- 2.5 mU/ml) and II (14.6 +/- 3.8 mU/ml) respectively.TNF administration was followed by a significant decline of plasma EPO both after the first (17.1 +/- 2.5 vs 9.0 +/- 1.5 mU/ml) and second cycle (14.6 +/- 3.8 vs 8.4 +/- 2.0 mU/ml) of TNF treatment. CONCLUSIONS: Patients with solid cancer and mild anaemia are characterised by inappropriate low plasma EPO concentration. Therapy with TNFalpha exerts a suppressive effect on EPO secretion in these patients.     

Whole blood superoxide anion generation and efficiency of some erythrocyte antioxidant systems during recombinant human erythropoietin therapy of uremic anemia

Six chronic uremic patients on regular hemodialysis treatment were given recombinant human erythropoietin (r-huEPO) in a dose of 50 U/kg of body weight intravenously thrice weekly for 14 weeks. Following r-huEPO therapy, unstimulated whole blood superoxide anion ( ₂) generation did not change significantly, while opsonized zymosan-stimulated whole blood ₂ generation increased. At the same time, erythrocyte superoxide dismutase and, in particular, glutathione peroxidase activities were found to be reducing with concomitant lowering of erythrocyte malonydialdehyde (MDA) concentrations and increase in plasma MDA concentrations.     

重组人红细胞生成素在妇科围手术期贫血治疗中的应用研究现状

抗对于妇科围手术期患者,由于术前贫血、术中失血或术后炎症,可能导致贫血状况愈加严重,而旨在改善患者预后和减少异体输血的妇科围手术期血液管理措施越来越被重视。重组人红细胞生成素能显著升高贫血患者血红蛋白水平并减少输血需求,其应用于围手术期贫血的纠正,已成为临床研究的新热点。综述重组人红细胞生成素治疗妇科围手术期贫血的作用机制、国内外临床研究及安全性研究。     

Etiology and treatment of malignancy-associated anaemia

Patients with cancer frequently develop anaemia. Various factors, including the type of malignancy and the intensity of chemotherapy influence the prevalence of anaemia and need of transfusions. Among the numerous causes of its development, the most frequent type is cancer anaemia, the so-called "anaemia of chronic disorders". Anaemia of chronic disorders is diagnosed when neoplastic disease is accompanied by an otherwise unexplained microcytic anaemia with compromised iron utilisation and decreased erythropoietin secretion. In 50-70% of patients with solid tumors or hematological malignancies, mainly with multiple myeloma and malignant lymphomas, transfusion can be avoided, or significantly decreased by the use of recombinant erythropoietin. This review provides tools to decide the best candidates for this treatment and a guideline to monitor its efficacy.     

Erythropoietin attenuated high glucose-induced apoptosis in cultured human aortic endothelial cells

High glucose-induced apoptosis in vascular endothelial cells may contribute to the acceleration of atherosclerosis associated with diabetes. Here, we show that erythropoietin attenuates high glucose-induced apoptosis in cultured human aortic endothelial cells (HAECs). Exposure of HAECs to high glucose level for 72h significantly increased the number of apoptotic cells compared with normal glucose level, as evaluated by TUNEL assay. Simultaneous addition of erythropoietin (100 U/ml) significantly attenuated high glucose-induced apoptosis. In parallel, exposure to high glucose level induced caspase-3 activation and erythropoietin also prevented it. Erythropoietin stimulated Akt phosphorylation in a dose-dependent manner (1-100 U/ml). PI3 kinase inhibitor, wortmannin or LY294002 eliminated erythropoietin's inhibitory effect on caspase-3 activity. In conclusion, erythropoietin may attenuate high glucose-induced endothelial cell apoptosis via PI-3 kinase pathway. Replacing therapy with erythropoietin is often used for correction of renal anemia, but may have potential in preventing atherosclerosis in diabetic patients with end-stage renal failure.     

Anaemia as a prognostic factor for the therapeutic effect of radiosensitizers

Results are reported of a clinical trial on the effect of metronidazole as an adjuvant radiosensitizer in the radiation treatment of cervix carcinomas in advanced stages. Analysis of the results was made with regard to the local clearance of the tumour and with haemoglobin level as a stratifying factor (less than 120 g/l or greater than/equal to 120 g/l at presentation). With no metronidazole treatment, the results in anaemic patients were inferior in comparison to patients with normal haemoglobin level. Metronidazole significantly improved the results in the anaemic cases, but had no effect on the non-anaemic patients. Without stratification with respect to anaemia, no significant difference between the metronidazole-treated and untreated control group was noted. It is concluded that anaemia has a prognostic value, and anaemic patients may represent a particular group for which hypoxic cell sensitizers can be expected to improve the effect of radiotherapy.     

Reduction in extracellular superoxide dismutase activity in African-American patients with hypertension

Superoxide anions react with nitric oxide to form peroxynitrite and hence reduce the bioavailability of nitric oxide in the arteries. Extracellular superoxide dismutase (EC-SOD) is a major superoxide scavenger in human plasma and vascular tissues. The objective of this study is to assess whether essential hypertension is associated with an alteration in EC-SOD activity. In this report, blood samples were obtained from hypertensive (n=39) and normotensive (n=37) African-Americans. Plasma EC-SOD activity was measured using in-gel activity staining and spectrophotometric assays, EC-SOD protein level was measured using Western blotting, nitrotyrosine was measured using slot blotting, 8-isoprostane was measured with an enzyme immunoassay, and plasma copper and zinc concentrations were measured using an atomic absorption assay. Our data demonstrate that the copper, zinc, and plasma EC-SOD protein concentrations in the hypertensive and normotensive subjects are indistinguishable. Compared to normotensive controls, hypertensive patients have significantly reduced plasma EC-SOD activity. Plasma nitrotyrosine and 8-isoprostane levels are significantly higher in the hypertensive patients than in normotensive controls. Results from this study suggest that a reduction in EC-SOD activity in hypertensive patients is not due to a down-regulation of the SOD3 gene (encoding EC-SOD) or deficiency in mineral cofactors. Furthermore, the reduced EC-SOD activity might be at least partially responsible for the increased oxidative stress, as reflected by increased plasma nitrotyrosine and 8-isoprostane, in hypertensive subjects.     

In vivo stimulatory effect of erythropoietin on endothelial nitric oxide synthase in cerebral arteries

The discovery of tissue protective effects of erythropoietin has stimulated significant interest in erythropoietin (Epo) as a novel therapeutic approach to vascular protection. The present study was designed to determine the cerebral vascular effects of recombinant Epo in vivo. Recombinant adenoviral vectors (10(9) plaque-forming units/animal) encoding genes for human erythropoietin (AdEpo) and beta-galactosidase (AdLacZ) were injected into the cisterna magna of rabbits. After 48 h, basilar arteries were harvested for analysis of vasomotor function, Western blotting, and measurement of cGMP levels. Gene transfer of AdEpo increased the expressions of recombinant Epo and its receptor in the basilar arteries. Arteries exposed to recombinant Epo demonstrated attenuation of contractile responses to histamine (10(-9) to 10(-5) mol/l) (P < 0.05, n = 5). Endothelium-dependent relaxations to acetylcholine (10(-9) to 10(-5) mol/l) were significantly augmented (P < 0.05, n = 5), whereas endothelium-independent relaxations to a nitric oxide (NO) donor 2-(N,N-diethylamino)diazenolate-2-oxide sodium salt remained unchanged in AdEpo-transduced basilar arteries. Transduction with AdEpo increased the protein expression of endothelial NO synthase (eNOS) and phosphorylated the S1177 form of the enzyme. Basal levels of cGMP were significantly elevated in arteries transduced with AdEpo consistent with increased NO production. Our studies suggest that in cerebral circulation, Epo enhances endothelium-dependent vasodilatation mediated by NO. This effect could play an important role in the vascular protective effect of Epo.     

Effect of Iron on Erythropoietin Production in Anaemic Piglets

In the present study the response of plasma erythropoietin to iron injection in anaemic piglets was examined. At the age of 16 days, 4 piglets from the same litter were given 180 mg iron subcutane-ously. After iron injection, blood samples for estimation of erythropoietin activity in plasma, haemoglobin concentration, and reticulocyte counts were taken every 6 or 12 h for 3 Vi days. Plasma erythropoietin activity was estimated by a monoclonal enzyme-im-munoassay (ELISA), developed for human erythropoietin. On the day of iron injection, haemoglobin concentration ranged between 41 and 48 g/1, reticulocyte counts from 9 to 17 percent, and plasma erythropoietin between 22 and 144 mU/ml. In 3 of the 4 piglets, iron injection resulted in a 2-6 fold increase in erythropoietin activity. Maximal eryth-ropoietin activities were observed 24-42 h after injection, and after 66 h, the activities were close to the pretreatment values. It is concluded that in our experiment, iron, per se, has stimulated erythropoietin production.