A comparison of the effects of renal artery constriction and anemia on the production of erythropoietin

It is generally assumed that the O₂ supply to the kidneys is the major determinant of the synthesis of erythropoietin (Ep). In the present study, the O₂ supply of the kidneys of rats was lowered by the reduction of renal blood flow (rbf). Plasma Ep was determined after about 18 h of bilateral application of Goldblatt clips with graded inner diameters. The results were compared to findings in anemic rats, in which the systemic O₂ supply was lowered by exchange transfusion of blood with plasma. We found a linear correlation between Ep levels in plasma and the degree of reduction of rbf. However, there was an exponential relationship between Ep levels and the concentration of hemoglobin in blood. In addition, the elevation of plasma Ep was only moderate, when rbf was reduced (maximum 0.07 IU Ep/ml plasma). The increase in Ep concentration was much more pronounced in anemia (up to about 7 IU Ep/ml plasma). From these results it may be concluded that decreasing oxygen supply to the kidney through reduction in renal blood flow (ischemic hypoxia) is less effective in increasing erythropoictin production than reducing the hemoglobin concentration (anemic hypoxia). The possibility must be considered that the increase in renal production of erythropoietin due to anemic hypoxia is triggered by one or more extrarenal signals.A preliminary report on the production of erythropoietin in anemic rats was presented at the XIth Int. Berlin Symposium on Erythroid Cells (Biomed Biochim Acta 46:S 304–S 308, 1987)     

Temporal pattern of erythropoietin titers in kidney tissue during hypoxic hypoxia

Plasma titers of erythropoietin (Ep) are known to increase initially during hypoxia and to return then towards prehypoxia values. To find out if this pattern of plasma Ep might be related to changes in the production of the hormone, I have compared plasma with kidney Ep titers in hypoxic rats. Rats were exposed to hypoxia in a hypobaric chamber at 0.42 atm for various time intervals for up to 4 days. Kidney Ep titers were assayed in extracts from kidneys that had been flushed free of blood in situ. It was found that kidneys of normal rats do not store significant amounts of Ep. Kidney Ep titers increased transiently during hypoxia. They reached maximum values after 6h and then declined to almost undetectable levels at continued hypoxia. In the plasma, maximum values were found after 12–18h of hypoxia. Additional studies were done on the effects of discontinuous hypoxia. It was found that, even after 3 days of previous hypoxia exposure, plasma and kidney Ep titers increased again in rats when these were maintained intermittently in normoxia for 18 h.It is concluded that the rise and fall in plasma Ep titers during hypoxia reflect similar changes in kidney Ep production.Supported by grants from the Deutsche Forschungsgemeinschaft (Je 95/3 and SFB 43)     

Demonstration of high levels of erythropoietin in rat kidneys following hypoxic hypoxia

Controversial hypotheses exist as to whether hypoxic kidneys produce biologically active erythropoietin (Ep) or an inactive erythropoietic factor that generates Ep from plasma protein in the blood. To clarify the role of the kidney in Ep production we attempted to extract Ep from kidneys of normal and of hypoxia exposed (6 h at 0.42 atm) Sprague-Dawley rats. Ep was measured in the microsomal fraction of kidney homogenates, using the exhypoxic polycythemic mouse assay for Ep. The Ep content was also determined in kidneys that were flushed free of blood with isotonic phosphate-buffer prior to extirpation.We found 0.04 U Ep/g in blood-depleted kidneys of normal rats. Upon exposure of the animals to hypoxia the Ep level increased to 0.92 U/g kidney. Ep levels were significantly higher in the kidney cortex than in the medulla. The erythropoietic activity in renal extracts was not enhanced after incubation of samples with homologous serum. Ep extracted from hypoxic kidneys behaved identically with plasma-Ep in the following biochemical tests: heat stability, affinity chromatography with wheat germ lectin, ion exchange chromatography, molecular sieve chromatography and neuraminidase inactivation.These studies support the hypothesis that kidney cortex cells are capable of producing biologically active Ep.Supported by grants from the Deutsche Forschungsgemeinschaft (Je 95/3 and SFB 43).Some of the material reported in this paper was presented in preliminary form at the 54. Meeting of the German Physiological Society (Bauer and Jelkmann 1981).     

Temporal relation between a hepatic erythropoietic factor and the site of rat erythropoietin production

Serum borne hepatic erythropoietic factor (HEF), which can stimulate hepatic erythropoietin (Ep) production in the adult rat, is found at elevated levels in the serum of partially hepatectomized rats and of rats subjected to hepatotoxic injury. It is also detected in sera of patients with liver disease. The purpose of the present study was to determine whether or not HEF activity is increased in the serum of the normal neonatal rat at a time when the liver is the primary site of Ep production. Our results show significantly increased HEF activity in the serum of young rats during the second to fifth weeks of life. Negligible activity was detected in rats over five weeks of age. In the rat, the kidney is reported to begin producing Ep by the third week of life and by the eighth week the kidney is the major site of synthesis with liver production at this age significantly diminished. Thus, our findings show a temporal relation between HEF activity in the serum and the reported transition from liver to kidney production of Ep.     

Effects of fasting on the hypoxia-induced erythropoietin production in rats

In order to test the hypothesis that the early cessation of erythropoietin (Ep) production during hypobaric hypoxia is induced by lowered food intake, we have compared the plasma Ep titer of rats after exposure to continuous hypoxia (42.6 kPa = 7000 m altitude) for 4 days with that in fed or fasted rats after exposure to discontinuous hypoxia. We found that plasma Ep was rather low after 4 days of continuous hypoxia. However, the Ep titer significantly rose again, when rats were maintained normoxic for 18 h and then exposed to repeated hypoxia for 6 h. Because this was also found in rats which were deprived of food during the normoxic interval and the second hypoxic period, we conclude that the fall of the Ep titer during continuous hypoxia is not primarily due to reduced food intake. In addition, our findings show that fasting per se lowers the Ep-response to hypoxia in normal rats but not exhypoxic rats.     

Immunoreactive erythropoietin and erythropoiesis stimulating factor(s) in plasma from hypertransfused neonatal and adult mice. Studies with a radioimmunoassay and a cell culture assay for erythropoietin

The objective was to study whether the high erythropoietic stimulatory activity found in plasma from neonatal mice during the growth period is erythropoietin (Ep) alone, or Ep in combination with other factors. Plasma from hypertransfused neonatal (20 d) and adult (13-20 weeks) mice were compared with a radioimmunoassay (RIA) and a cell culture assay for Ep. The RIA determines immunoreactive Ep (iEp) while the cell culture assay reflects erythropoiesis stimulating factor(s) (ESF). Compared to control values, hypertransfusion resulting in PCVs of 55% and higher reduced the mean iEp levels in neonatal and adult mice by 82% and 38%, respectively (P less than 0.01). There was no detectable difference between the mean iEp levels of hypertransfused neonatal and adult animals (P greater than 0.3). The parallel ESF data showed a reduction in mean plasma ESF levels by 68% in hypertransfused neonatal and 72% in hypertransfused adult animals (P less than 0.001). And notably, in contrast to the iEp data, the mean ESF level found in hypertransfused neonatal mice with PCVs of 55% and higher was significantly above that of hypertransfused adult animals (P less than 0.001). No correlation was found between PCV and iEp (r less than 0.4, P greater than 0.1) or ESF (r less than 0.2, P greater than 0.2) in hypertransfused animals. The parallel data from the two Ep assays show that plasma from hypertransfused 20-d-old mice contain one or more erythropoietic stimulatory factors not detected by the RIA. It is concluded that part of the high erythropoietic stimulatory activity found in plasma from neonatal mice is due to non-Ep factors.     

Correlation of plasma erythropoiesis stimulating factor(s) and immunoreactive erythropoietin levels during rapid growth in the mouse

During the early neonatal period of rapid growth in the mouse, increased plasma levels of erythropoiesis stimulating factor(s) (ESF) have been found when measured by an in-vitro bioassay technique. It is unclear whether these increased ESF levels represent increased levels of circulating erythropoietin (Ep) alone or Ep in combination with other less-defined erythropoietic stimulatory factors. To examine this issue, plasma from neonatal mice of varying post-natal ages and from normoxic and hypoxic adult mice was studied. We found that plasma Ep levels measured by radioimmunoassay (RIA) correlated significantly with in-vitro bioassayed ESF levels (r = 0.84, P less than 0.0001, n = 21). Although an in-vivo bioassay for plasma Ep proved too insensitive for rigorous correlation with data from the RIA and in-vitro bioassay, the in-vivo data were in qualitative agreement with the other two, more sensitive, assays. In all three assays the highest plasma levels were observed in the 20-day-old mice and in adult mice which had been subjected to hypobaric hypoxia for 8 h. Based on the strong agreement of the results obtained with the RIA and the in-vitro bioassay in both neonatal and adult mouse plasma, we conclude that the high plasma ESF levels of 20-day-old mice measured with the in-vitro bioassay are largely immunochemically identifiable Ep. However, the data also suggest the presence of non-Ep factors in neonatal plasma which stimulate the in-vitro bioassay.     

Erythropoietin in thrombotic thrombocytopenic purpura and acute renal failure

Summary In this study, erythropoietin serum levels were serially determined in eight patients with acute renal failure to get a lead on the etiology of anemia in acute renal failure and to address the relationship between erythropoietin synthesis and renal excretory performance. Erythropoietin serum levels rapidly decreased after onset of acute renal failure to values of 12.8 ± 10.3 mU/ml compared to 16.8 ± 9.4 mU/ml in healthy controls. After restoration of renal function, erythropoietin levels climbed slowly in six patients (15.2 ±5.3 mU/ml), and in relation to prolonged anemia in these patients, a relative deficiency of erythropoietin could be observed. In one patient with thrombotic thrombocytopenic purpura causing acute renal failure, the decline of erythropoietin secretion was not observed, and in a phase of the disease when plasma exchange therapy was interrupted, markedly increased erythropoietin levels, up to 182 mU/ml, were detected despite the renal failure. Focusing on erythropoietin secretion in thrombotic thrombocytopenic purpura, we followed hormone synthesis in two other patients with the same disease, one of whom had mild renal insufficiency and one had normal renal function. High erythropoietin levels of up to 205 mU/ml were found in these patients, similar to the peak levels found in the patient with complete renal failure. Plasmapheresis treatment reduced erythropoietin production in all three patients with thrombotic thrombocytopenic purpura. In summary, our study indicates that in most cases of acute renal failure, erythropoietin synthesis is compromised and may contribute to the development of anemia in renal failure and aggravate the persistence of anemia after restoration of renal function. Comparing erythropoietin production in patients with acute renal failure and in those with thrombotic thrombocytopenic purpura with varying renal involvement we conclude that erythropoietin secretion is not closely linked to renal excetory performance, and that hemolysis or other stimuli in thrombotic thrombocytopenic purpura can override the decline of erythropoietin production implied by renal failure.Abbreviations ARF acute renal failure - EPO erythropoietin - TTP thrombotic thrombocytopenic purpura     

Increased red blood cell protoporphyrin in thalassemia: a result of relative iron deficiency

Erythrocyte protoporphyrin (EP) was measured in 50 normal control subjects, 22 iron-responsive anemic subjects, and in 106 patients with thalassemic diseases. All normal subjects had EP of less than 80 micrograms/dL red blood cells, whereas all iron-deficiency subjects had EP of more than 80 micrograms/dL red blood cells. Six of 22 heterozygotes for thalassemias had elevated EP, and all of these had transferrin iron saturation of less than 16%, reflecting a complicating iron deficiency. Among 52 patients with beta-thalassemia/hemoglobin (Hb) E disease, 26.9% had elevated EP levels, and among 32 patients with Hb H disease, 40.6% had elevated EP. These elevated EP levels were associated with transferrin iron saturation between 18 and 44%. In none of the thalassemic patients with transferrin iron saturation above 44% was EP elevated. These findings suggest that elevation of EP in some thalassemic patients causally is related to iron supply inadequate for the massively expanded erythropoiesis. This relative iron deficiency in thalassemia occurs at a transferrin iron saturation level usually considered to be normal. These relationships demonstrate the need for an increased iron supply in patients with erythroid marrow hyperplasia, if erythropoiesis is to proceed at maximal rates.     

Immunoreactive erythropoietin and erythropoiesis stimulating factor(s) in plasma from hyper-transfused neonatal and adult mice. Studies with a radioimmunoassay and a cell culture assay for erythropoietin

The objective was to study whether the high erythropoietic stimulatory activity found in plasma from neonatal mice during the growth period is erythropoietin (Ep) alone, or Ep in combination with other factors. Plasma from hypertransfused neonatal (20 d) and adult (13–20 weeks) mice were compared with a radioimmunoassay (RIA) and a cell culture assay for Ep. The RIA determines immunoreactive Ep (iEp) while the cell culture assay reflects erythropoiesis stimulating factor(s) (ESF). Compared to control values, hypertransfusion resulting in PCVs of 55% and higher reduced the mean iEp levels in neonatal and adult mice by 82% and 38%, respectively (P < 0.01). There was no detectable difference between the mean iEp levels of hypertransfused neonatal and adult animals (P > 0.3). The parallel ESF data showed a reduction in mean plasma ESF levels by 68% in hypertransfused neonatal and 72% in hypertransfused adult animals (P < 0.001). And notably, in contrast to the iEp data, the mean ESF level found in hypertransfused neonatal mice with PCVs of 55% and higher was significantly above that of hypertransfused adult animals (P < 0.001). No correlation was found between PCV and iEp (r < 0.4, P > 0.1) or ESF (r < 0.2, P > 0.2) in hypertransfused animals. The parallel data from the two Ep assays show that plasma from hypertransfused 20-d-old mice contain one or more erythropoietic stimulatory factors not detected by the RIA. It is concluded that part of the high erythropoietic stimulatory activity found in plasma from neonatal mice is due to non-Ep factors.     

Reflex responses in plasma catecholamines caused by static contraction of skeletal muscle.

To examine a hypothesis of whether static muscle contraction produces a release of catecholamines from the adrenal medulla via reflex stimulation of preganglionic adrenal sympathetic nerve activity induced by receptors in the contracting muscle, we compared the reflex responses in a concentration of epinephrine (Ep) and norepinephrine (NEp) in arterial plasma during static contraction and during a mechanical stretch of the hindlimb triceps surae muscle in anesthetized cats. Static contraction was evoked by electrically stimulating the peripheral ends of the cut L(7) and S(1) ventral roots at 20 or 40 Hz. Mean arterial pressure (MAP) and heart rate (HR) increased 23 +/- 3.1 mmHg and 19 +/- 4.3 beats/min during static contraction. Ep in arterial plasma increased 0.18 +/- 0.072 ng/ml over the control of 0.14 +/- 0.051 ng/ml within 1 min from the onset of static contraction, and NEp increased 0.47 +/- 0.087 ng/ml over the control of 0.71 +/- 0.108 ng/ml. Following a neuromuscular blockade, although the same ventral root stimulation failed to produce the cardiovascular and plasma catecholamine responses, the mechanical stretch of the muscle increased MAP, HR, and plasma Ep, but not plasma NEp. With bilateral adrenalectomy, the baseline Ep became negligible (0.012 +/- 0.001 ng/ml) and the baseline NEp was lowered to 0.52 +/- 0.109 ng/ml. Neither static contraction nor mechanical stretch produced significant responses in plasma Ep and NEp following the adrenalectomy. These results suggest that static muscle contraction augments preganglionic adrenal sympathetic nerve activity, which in turn secretes epinephrine from the adrenal medulla into plasma. A muscle mechanoreflex from the contracting muscle may play a role in stimulation of the adrenal sympathetic nerve activity.     

Increased and highly stable levels of functional soluble interleukin-6 receptor in sera of patients with monoclonal gammopathy

Soluble human interleukin-6 receptor (sIL-6R) was measured in the serum of 30 healthy individuals, 32 individuals with monoclonal gammopathy of undetermined significance (MGUS), 20 patients with early multiple myeloma (MM) and 54 patients with overt MM. The serum activity recognized by an immunoradiometric assay was determined to be sIL-6R, because of its binding capacity to IL-6 and its molecular mass of 55 kDa. All sera of healthy individuals contained sIL-6R (mean value: 89 ng/ml, range 17-300 ng/ml). Serum sIL-6R levels were increased by 51% in patients with MGUS (mean value: 135 ng/ml, p<0.005), by 44% in patients with early myeloma (mean value: 128 ng/ml, p<0.001) and by 116 % in patients with overt MM (mean value: 193 ng/ml, p<0.001). In patients with MM, a complete lack of correlation (p>0.7) was found between serum sIL-6R levels and other previously recognized prognostic factors in this disease, particularly serum IL-6 levels and those factors related to tumor cell mass. The independence of serum sIL-6R levels on tumor cell mass was directly demonstrated by studying four patients with MM treated with autologous bone marrow transplantation for periods of between 320 and 760 days. These levels were found to be remarkably stable and constant, independent of whether patients relapsed or achieved complete remission. Finally, physiological concentrations of sIL-6R were found to increase by tenfold the sensitivity of human myeloma cell lines to IL-6. These observations suggest a high control of the sIL-6R level in vivo, and, possibly, an important functional role of this circulating protein in patients with monoclonal gammopathies.     

Erythropoietin and improvement of anemia in long-term hemodialysis patients

Two groups, with 4 patients each were selected for study out of 155 patients on regular hemodialysis (HD): Group I, with hematocrit (PCV) less than 20% and group II, with PCV greater than 30%. The patients in both groups had been anemic at the start of HD treatment, but a significant improvement in their anemia had occurred only among the patients in the Group II. The main difference between the two patient groups, other than the degree of anemia, was found to be in serum erythropoietin (Ep) levels. No significant differences were observed between the two groups in serum urea, creatinine, parathyroid hormone or CFU-E growth inhibition. Acquired cystic disease of the kidney was found in five patients from group I, and in 11 patients from group II. The correlation between the number of cysts in the kidneys and the patient's PCV and serum Ep levels proved significantly positive. The results presented could be regarded as another proof that diseased kidney is capable of functioning as an Ep producing organ despite the loss of excretory function.     

Antibody to hepatitis C virus in multiply transfused patients with thalassaemia major.

Seventeen of 73 (23.3%) multiply transfused patients with thalassaemia major (age range, 1-39 years) tested positive for antibody to hepatitis C virus (anti-HCV). Eleven of the 24 patients regularly transfused in countries outside Britain were anti-HCV seropositive; only six of the 49 regularly transfused in Britain were seropositive. The incidence of anti-HBs and anti-HBc was similar to that of anti-HCV in both the British and foreign patients. The anti-HCV seropositive patients showed significantly higher plasma aspartate aminotransferase activities (AST), mean (SD) 10.2 (70.3) U/l, and serum ferritin concentrations, 4067 (2708) micrograms/l, than the anti-HCV seronegative patients (AST, 33.9 (15.6) U/l; serum ferritin 2051 (2092) U/l), respectively. Among the 36 patients who had earlier undergone liver biopsy 10 of 21 with histological features of chronic active hepatitis or cirrhosis, or both, were seropositive for anti-HCV whereas only one of 15 without histological evidence of chronic viral hepatitis was seropositive for anti-HCV. It is concluded that HCV is a major cause of chronic hepatitis in patients with thalassaemia major and is associated with raised AST activity and serum ferritin concentration compared with patients seronegative for anti-HCV.     

Iron state and hepatic disease in patients with thalassaemia major, treated with long term subcutaneous desferrioxamine.

Liver biopsies were performed on 51 regularly transfused patients with beta thalassaemia, age range 5-36 (mean 18.6) years, who had received regular subcutaneous desferrioxamine (DFX) treatment for periods between one and eight years (40 for eight years). The biopsy specimens were examined by light microscopy and immunofluorescence for hepatitis B virus surface and core antigens (HBsAg and HBcAg), and the iron content was determined chemically. The results were compared with serum ferritin concentration and aspartate transaminase (AST) activity and with hepatitis B virus serology. Biopsy specimens, in which chemical liver iron had been determined in 12, were also available from 17 patients. Mean serum ferritin (+/- SD) had fallen from 5885 (3245) micrograms/l to 1638 (976) micrograms/l in 36 patients after eight years' chelation, while mean (+/- SD) liver iron concentration had fallen from 2945 (900) micrograms/100 mg dry weight to 857 (435) micrograms/100 mg dry weight in 12 of them. All biopsy specimens examined were negative for HBs and HBc antigens. The presence of histological features of hepatitis was associated with increased liver iron content, increased fibrosis, and with progression of fibrosis between the two biopsies. Procollagen III peptide was assayed in 28 patients but did not correlate with the degree of hepatitis, fibrosis, or with chemical liver iron content. We conclude that with regular subcutaneous DFX, mean concentrations of serum ferritin and liver iron are maintained in these patients at about five and 10 times the normal value, respectively, and that progression of liver damage is more likely to be due to viral hepatitis, presumably related to the parenterally transmitted non-A, non-B agents than to iron overload.     

Episodic hypoxia evokes long-term facilitation of genioglossus muscle activity in neonatal rats

The aim of this study was to determine if episodic hypoxia evokes persistent increases of genioglossus muscle (GG) activity, termed long-term facilitation (LTF), in neonatal rats in vivo . Experiments were performed on anaesthetized, spontaneously breathing, intubated neonatal rats (postnatal days (P) 3–7), divided into three groups. The first group ( n = 8) was subjected to three 5-min periods of hypoxia (5% O₂–95% N₂) alternating with 5 min periods of room air. The second group ( n = 8) was exposed to 15 min of continuous hypoxia. The third ( n = 4) group was not exposed to hypoxia and served as a control. GG EMG activity and airflow were recorded before, during and for 60 min after episodic and continuous hypoxic exposure. During hypoxia, GG EMG burst amplitude and tidal volume ( V _T ) significantly increased compared to baseline levels (episodic protocol: mean ± s.e.m ; 324 ± 59% of control and 0.13 ± 0.007 versus 0.09 ± 0.005 ml, respectively; continuous protocol: 259 ± 30% of control and 0.16 ± 0.005 versus 0.09 ± 0.007 ml, respectively; P < 0.05). After the episodic protocol, GG EMG burst amplitude transiently returned to baseline; over the next 60 min, burst amplitude progressively increased to levels significantly greater than baseline (238 ± 40% at 60 min; P < 0.05), without any significant increase in V _T and respiratory frequency ( P > 0.05). After the continuous protocol, there was no lasting increase in GG EMG burst amplitude. We conclude that LTF of upper airway muscles is an adaptive respiratory behaviour present from birth.     

Hepatitis B virus infection and the response to erythropoietin in end-stage renal disease

In patients with end-stage renal disease (ESRD), viral or bacterial infections are postulated to abolish or impair response to recombinant erythropoietin (Epogen). However, previous reports revealed that response to Epogen among hemodialysis patients with a particular viral infection--human immunodeficiency virus (HIV)--seems to be variable and is independent of illness severity. To further explore the issue of response to Epogen in hemodialysis patients with viral infection, we retrospectively studied four patients with hepatitis B virus infection over a 3 month period to compare their response to Epogen and endogenous erythropoietin levels with those of a control group of patients without hepatitis B virus infection. Weekly predialysis hematocrit, and monthly serum albumin concentration, transferrin saturation as well as percent reduction of urea were obtained from patient records, and mean values were calculated for each subject. Mean age of the patients (n = 4) was 63 +/- 7.5 years compared with 55 +/- 23 years for the control subjects (n = 4)(p = 0.02). The mean hematocrit of the study patients was 33.7 +/- 2.8% compared with 34.7 +/- 4.9% in the control subjects (p = 0.49), and the mean endogenous erythropoietin level in the study patients was 27 +/- 22 mlU/ml compared with 5.7 +/- 1.9 mlU/ml in the control group (p = 0.001). The mean dose of thrice weekly Epogen, both at onset of the study and when endogenous erythropoietin was measured, was 61 +/- 19 U/kg body weight in the patients, compared with 74 +/- 8 U/kg body weight in the control subjects (p = 0.002). We conclude that patients with ESRD and hepatitis B surface antigenemia respond to Epogen as well as their counterparts without hepatitis B virus infection. In addition, patients with hepatitis B surface antigenemia have much higher serum levels of endogenous erythropoietin and require less exogenous erythropoietin injections than their counterparts.     

Anemia in patients on chronic hemodialysis in Cameroon: prevalence,characteristics and management in low resources setting

BackgroundAnemia is a common complication of chronic kidney disease. We investigated the prevalence, characteristics and management of anemia in patients on chronic hemodialysis and assessed the response to blood-transfusion based management in Cameroon.MethodsThis was a cohort study of five months'' duration (August–December 2008) conducted at the Yaoundé General Hospital''s hemodialysis center, involving 95 patients (67 men, 70.5%) on chronic hemodialysis by a native arteriovenous fistula. A monthly evaluation included full blood counts, number of pints of red cell concentrates transfused, and vital status.ResultsAt baseline, 75 (79%) patients had anemia which was microcytic and hypochromic in 32 (43%). Anemia was corrected in 67 (70.5%) patients using blood transfusion only, while 28 (29.5%) patients were receiving erythropoietin (11 regularly, 39%). Only 77.2% of 342 pints (median 3.0, range 0–17 per patients) of red cell concentrates prescribed were effectively received during the follow-up at an unacceptably high cost to patients and families. Mean hemoglobin and mean corpuscular hemoglobin levels remained stable during follow-up, while mean corpuscular volume increased. Erythropoietin treatment was the main determinant of favorable trajectories of hematological markers.ConclusionsPatients on chronic hemodialysis have predominantly microcytic hypochromic anemia, with limited capacity for correction using blood transfusion.     

Experimental acute myocardial infarction in rats: HIF-1α, caspase-3, erythropoietin and erythropoietin receptor expression and the cardioprotective effects of two different erythropoietin doses

The cardioprotective effects of two different doses of erythropoietin administration were analyzed in rats with experimental myocardial infarction. None, saline, standard-dose (5000 U kg⁻¹) and high-dose (10,000 U kg⁻¹) of human recombinant erythropoietin alpha were administered intraperitoneally in Wistar rats with myocardial infarction induced by coronary artery ligation. Infarct sizes measured after triphenyltetrazolium chloride staining, levels of biochemical markers, histopathology examined by light and electron microscopy, and immunohistochemical expressions of erythropoietin, erythropoietin receptor, hypoxia inducible factor-1α and caspase-3, were analyzed. Lower scores of infarction and hemorrhage, lower number of macrophages and higher score of vascularization surrounding the infarct area were observed in the erythropoietin administered groups (p < 0.05). Erythropoietin administration after myocardial infarction reduced the area of infarction and hemorrhage. There were hypoxia inducible factor-1α and caspase-3 expressions in the marginal area, and erythropoietin and erythropoietin receptor expression in both marginal and normal areas (p < 0.001). Vascularization, erythropoietin expression in the normal area and vascular erythropoietin expression were positively correlated with human erythropoietin levels. The cardioprotective effects of erythropoietin treatment were independent of endogenous erythropoietin/erythropoietin receptor activity. Moreover exogenous erythropoietin treatment did not suppress endogenous erythropoietin. Erythropoietin administration after myocardial infarction reduced caspase 3 expression (apoptotic activity) and induced neovascularization around the infarct area. Higher erythropoietin administration did not provide an additional benefit over the standard-dose in myocardial protection.     

Assay of erythropoietin in plasma by enzyme-linked immunosorbent assay

Using an enzyme linked immunosolvent assay kit supplied by Toyobo Co., erythropoietin (EPO) concentration in plasma was measured. Normal 100 samples showed a logarithmic distribution in EPO concentrations and normal range was between 5.4-32.5 mU/ml (mean +/- 2 SD). Coefficient variations (C.V.) of 3 samples continuously assayed were 3.8%, 6.5%, and 9.1% and C.V. of 3 samples assayed day by day were 3.6%, 7.2%, and 11.5%. Dilution test revealed that 3 samples diluted to 75%, 50%, and 25% were on each line which go through zero point. After the addition of 5.0, 15.0, and 35.0 mU/ml of EPO to the 3 samples, assay of EPO revealed 95.5 +/- 6.3% (mean +/- SD) of recovery. Assay of EPO in plasma from 19 patients with aplastic anemia revealed that all samples were higher than normal range and that 4 samples from the patients with severe aplastic anemia (less than 8.0 g/dl of hemoglobin) showed higher than 3,000 mU/ml. Furthermore, 67% (14/21) of samples from patients with leukemia showed higher than normal range in EPO concentration. EPO concentration in plasma from 17 patients with chronic renal failure were within normal range although the patients showed anemia.