The Effect of Intramuscular Iron Therapy on Hematological Values in Normal Men and Women

It has been claimed repeatedly that iron stimulates hemoglobin formation in normal men and women. Because of the inconclusive evidence in the literature, the possible stimulatory action of iron on normal hemoglobin synthesis was reinvestigated by evaluating the effect of 1000 mg. of intramuscular iron on hematological parameters in six normal men and six normal women over a six-month period. Determinations of red cell and hemoglobin mass after three and six months and monthly determinations of hemoglobin concentration, packed cell volume, red cell count, reticulocyte count, mean corpuscular volume and mean corpuscular hemoglobin concentration showed no significant rise in either the men or the women. It is concluded that there is no demonstrable proof that the administration of iron stimulates erythropoiesis or hemoglobin synthesis in iron-sufficient normal men and women.     

Iron uptake by glial cells

Dynamic studies of iron metabolism in brain are generally unavailable despite the fact that a number of neurologic conditions are associated with excessive accumulation of iron in central nervous tissue. Cortical non-neuronal (glial) cultures were prepared from fetal mouse brain. After 13 days the cultures were exposed to radiolabeled iron. Brisk and linear total iron uptake and ferritin iron uptake occurred over 4 hours. When methylamine or ammonium chloride was added, (both known inhibitors of transferrin iron release because of their lysosomotropic properties), total iron uptake was diminished. Further studies indicated that meth-ylamine inhibits glial cell ferritin iron incorporation. Glial cell iron transport is similar to previously reported neuronal cell iron transport (1) but glial cell iron uptake proceeds at a faster rate and is more susceptible to the inhibition of certain lysosomotropic agents. The data reinforces the likelihood that iron uptake by nervous tissues is transferrin-mediated.     

Decreased bone marrow iron in chronic granulocytic leukaemia: a consistent finding not reflecting iron deficiency

The iron status of 50 patients with Ph'-positive chronic granulocytic leukaemia (CGL) was evaluated at diagnosis by means of bone marrow and blood studies. A decreased or absent iron in semiquantitative estimation on bone marrow smears was observed in 92% of patients, and 88% had a low sideroblast score. In contrast, normal Hb and serum iron concentrations were found in the majority of cases, and only two out of the 50 patients displayed a decreased serum ferritin. To ascertain whether the bone marrow pattern of iron depletion could be due to an expansion of the red cell mass, the latter parameter was measured by isotopic methods in a subgroup of 11 patients. Normal or slightly increased values were obtained in all cases. We conclude that absent or decreased marrow iron is a common feature in the chronic phase of CGL, that generally does not reflect true iron deficiency. Since such a finding is also usual in polycythaemia vera and idiopathic myelofibrosis, it should be included among the features shared by the chronic myeloproliferative disorders.     

Iron Metabolism in Patients Undergoing Regular Dialysis Therapy

Thirteen patients with chronic renal failure maintained on regular renal dialysis were studied. Seven proved to have iron deficiency on the basis of marrow iron studies, reticulocyte iron uptake, and saturation of the serum iron-binding capacity. They absorbed iron when given it by mouth and were able to utilize it for haemoglobin formation. Iron-deficient patients given 600 mg of ferrous sulphate daily for three months showed an increase in haemoglobin, but the failure to replace stores of iron is probably related to their relatively limited ability to absorb iron and the variable but sometimes considerable blood loss occurring with each dialysis.The loss may be occult, and prolonged iron therapy may be required. This is most safely achieved by giving iron by mouth.     

Increase in hematocrit, hemoglobin and red cell mass in normal mice after treatment with cyclic AMP (38543).

Chronic treatment of normal mice with either dibutyryl cyclic AMP or erythropoietin produced elevations in the hematocrit, hemoglobin concentration and red cell mass when compared to these same hematological parameters in untreated mice. Dibutyryl cyclic AMP increased red cell mass by 46% while ESF treatment resulted in a 56% increase in red cell mass. These studies confirm earlier reports of the effects of cyclic AMP in increasing radioactive iron incorporation into red cells and further indicate that this change is associated with an absolute increase renal cyclic AMP concentrations probably stimulate erythropoiesis as a consequence of increased kidney production of erythropoietin.     

Ceruloplasmin expression and its role in iron transport in C6 cells

Ceruloplasmin (CP) is essential for brain iron homeostasis. However, little is known about the effect of iron on CP expression in the brain. Also, the role of CP in brain iron transport has not been well determined. In this study, we investigated the effects of iron on CP expression and the role of CP in iron transport in the C6 rat glioma cells. Our data showed that treatment of the cells with iron (cell iron overload) or iron chelators (cell iron deficiency) did not induce a significant change in the expression of CP mRNA. However, western blotting analysis demonstrated that cell iron overload induced a significant decrease in CP protein content in the cells and that treatment with iron chelators led to a significant increase in CP protein level in the cells. These findings suggest a translational regulation of CP expression by iron in the cells. We also examined the effects of CP on iron transport in the cells. We found that glycosylphosphatidylinositol-anchored CP did not have any impact on iron uptake by normal iron or iron-deficient cells nor on iron release from normal iron or iron-sufficient cells. However, low concentrations of soluble CP (2-8 microg/ml) increased iron uptake by iron-deficient C6 glioma cells, while the same concentrations of CP had no effect on iron uptake by normal iron cells and iron release from normal iron and iron-sufficient cells. The possible reason for the difference between our results in vitro and those obtained from in vivo studies was discussed.     

Iron metabolism pathways in the rat hepatocyte

A small to moderate inhibitory effect of iron uptake by isolated rat hepatocytes in short-term studies was seen with oxidative phosphorylation and electron transport inhibitors, and no inhibition by agents affecting pinocytosis. Intracellular transferrin was able to donate iron to the small-molecular weight iron pool, and the latter was able to transfer, by a process not requiring energy or movement of serum transferrin, iron to ferritin. Serum transferrin was not able to lose iron to any cytosol components. Reducing agents were not able to abstract iron from rat serum transferrin to any great extent. It is concluded that iron is taken up by the rat hepatocyte from serum transferrin by a process not requiring energy or movement of serum transferrin into the cell interior; and that intracellular transferrin is involved in acquiring iron from serum transferrin at the cell surface, with iron then being transferred to the small-molecular weight iron pool and hence to ferritin. It is also proposed that intracellular transferrins may have the general function of interacting with serum transferrin at cell surfaces.     

Iron storage in Mycoplasma capricolum.

Considerable quantities or iron were incorporated into the Mycoplasma capricolum cell membrane. Mossbauer studies showed that the iron is in a form which becomes magnetically ordered at low temperatures. The iron-enriched cells contained membrane-bound electron-dense particles of about 6.0 nm in diameter.     

Iron Transport in Escherichia coli: Uptake and Modification of Ferrichrome

During the transport of iron as ferrichrome complex into cells of Escherichia coli K-12, the ligand was modified and excreted into the medium. The rate of the formation of the modified product corresponded with the rate of iron transport. The modified product showed a decreased affinity for ferric iron and did not serve as an effective iron ionophore. After all of the ferrichrome had been converted, the modified product was taken up into the cell in an iron-free form. The uptake of ferrichrome and of the modified product depended on the transport system specified by the tonA and tonB genes. The modified product could be converted back into ferrichrome by mild acid or alkaline hydrolysis. One mole of acetate was released per mole of ferrichrome. It is proposed that one N-hydroxyl group of ferrichrome is acetylated to explain the low affinity for iron as the N-hydroxyl groups form the ligands for iron (III). A weak ester linkage by which the acetyl group is covalently bonded would account for the easy hydrolysis. The iron-free form of ferrichrome, deferri-ferrichrome, was also rapidly converted when incubated with cells with a functional transport system. It is therefore likely that iron is released from ferrichrome by reduction before modification takes place. The conversion of the ligand could be a mechanism by which cells rid themselves of a potentially deleterious ligand for iron in the cytoplasm. A possible role in ferrichrome transport is discussed.     

Iron stores in essential thrombocythaemia. A study of 26 patients

The iron status of 26 patients with essential thrombocythaemia (ET) was evaluated at diagnosis by means of bone marrow iron and blood studies, including serum ferritin determination. Nine patients were males, 17 females, and the mean age was 53 years (range 7-81). A decreased or absent iron level by semiquantitative estimation on bone marrow smears was observed in 77% of patients, and 81% had a low sideroblast score. Such a marrow pattern of iron depletion was equally distributed between both sexes. Contrasting with this, normal Hb, MCV, serum iron and serum ferritin were registered in the majority of cases. According to these results, absent or decreased marrow iron would be a common feature in ET, generally not reflecting true iron deficiency, as it occurs in the remaining chronic myeloproliferative disorders. Thus, in patients in whom ET is suspected, the diagnostic criterion of ruling out iron deficiency would be better served by serum ferritin measurement than by bone marrow iron estimation.     

Effect of Ferriprotoporphyrin IX and Non-heme Iron on the Ca2+ Pump of Intact Human Red Cells

Previous studies have shown that ferriprotoporphyrin IX (FP) and non-heme iron have a marked inhibitory effect on the Ca²⁺-Mg²⁺-ATPase activity of isolated red cell membranes, the biochemical counterpart of the plasma membrane Ca²⁺ pump (PMCA). High levels of membrane-bound FP and non-heme iron have been found in abnormal red cells such as sickle cells and malaria-infected red cells, associated with a reduced life span. It was important to establish whether sublytic concentrations of FP and non-heme iron would also inhibit the PMCA in normal red cells, to assess the possible role of these agents in the altered Ca²⁺ homeostasis of abnormal cells. Active Ca²⁺ extrusion by the plasma membrane Ca²⁺ pump was measured in intact red cells that had been briefly preloaded with Ca²⁺ by means of the ionophore A23187. The FP and nonheme iron concentrations used in this study were within the range of those applied to the isolated red cell membrane preparations. The results showed that FP caused a marginal inhibition (∼20%) of pump-mediated Ca²⁺ extrusion and that non-heme iron induced a slight stimulation of the Ca²⁺ efflux (11–20%), in contrast to the marked inhibitory effects on the Ca²⁺-Mg²⁺-ATPase of isolated membranes. Thus, FP and non-heme iron are unlikely to play a significant role in the altered Ca²⁺ homeostasis of abnormal red cells. Received: 22 November 1999/Revised: 29 February 2000     

Organic-acid transport in resealed haemoglobin-containing human erythrocyte ''ghosts''.

The transport of organic acids across the membrane of resealed haemoglobin-containing erythrocyte 'ghosts' prepared by a dialysis technique has been studied. The present work forms part of studies directed towards the use of erythrocyte cellular carriers in enzyme-replacement therapy of inherited metabolic diseases. Oxalic acid, glycollic acid and glyoxylic acid were taken as representative of aliphatic acids of low molecular mass and benzoic and cinnamic acids as representative of unsubstituted aromatic acids. These selected acids are important in the diseases with which the present work is concerned. Comparison of influx and efflux transport characteristics showed that erythrocyte 'ghosts' retain transport properties closely similar to those of normal erythrocytes. Rapid transport was observed with all organic acids studied and there was a linear relationship between initial amount of influx and external concentration of aliphatic acid. Saturation of the transport system was not observed up to 1 mM external concentration, and the presence of plasma in the external medium had no effect on transport characteristics. Transport in intact erythrocytes and prepared erythrocyte 'ghosts' from patients with hyperoxaluria was also studied.     

Transient Iron-Overload with Bleomycin-Detectable Iron Present During Cardiopulmonary Bypass Surgery

Extracorporeal circulation of blood during cardiopulmonary bypass surgery exposes cells to non-physiological surfaces and shear stress which can activate several regulatory cascades, and neutrophils to release superoxide and hydrogen peroxide. Shear stresses generated by pumps and suction systems cause lysis of red blood cells and the release of haemoglobin. Together the release of reactive forms of oxygen and haemoglobin can lead to the appearance of low molecular mass chelatable iron (bleomycin-detectable iron). All patients undergoing open heart surgery appear to release iron to plasma transferrin, increasing its iron saturation. In 13% of patients, however, the transferrin became fully iron-saturated, and by the end of open-heart surgery we could detect bleomycin-chelatable iron in the plasma. Saturation of transferrin with iron eliminates its iron-binding antioxidant properties, which can result in a stimulation of iron-dependent radical damage to selected detector molecules.     

Transient Iron-Overload with Bleomycin-Detectable Iron Present During Cardiopulmonary Bypass Surgery

Extracorporeal circulation of blood during cardiopulmonary bypass surgery exposes cells to non-physiological surfaces and shear stress which can activate several regulatory cascades, and neutrophils to release superoxide and hydrogen peroxide. Shear stresses generated by pumps and suction systems cause lysis of red blood cells and the release of haemoglobin. Together the release of reactive forms of oxygen and haemoglobin can lead to the appearance of low molecular mass chelatable iron (bleomycin-detectable iron). All patients undergoing open heart surgery appear to release iron to plasma transferrin, increasing its iron saturation. In 13% of patients, however, the transferrin became fully iron-saturated, and by the end of open-heart surgery we could detect bleomycin-chelatable iron in the plasma. Saturation of transferrin with iron eliminates its iron-binding antioxidant properties, which can result in a stimulation of iron-dependent radical damage to selected detector molecules.     

Association of Iodine and Iron with Thyroid Function

Iodine and iron are essential elements for healthy thyroid function. However, little is known about the association of iron and iodine with thyroid function in the general US population. We investigated iron and iodine status in relation to concentrations of thyroid hormones. We included 7672 participants aged 20 and older from three surveys (2007–2008, 2009–2010, and 2011–2012) of the National Health and Nutrition Examination Survey. Serum thyroid measures (including free and total T3 and T4, and TSH), serum iron concentration, and urinary iodine concentrations were measured. Multivariate linear regression models were conducted with serum thyroid measures as dependent variables and combinations of serum iron concentration and urinary iodine concentration as predictors with covariate adjustment. Logistic regression models were performed with TSH levels (low, normal, and high) and combinations of serum iron concentration and urinary iodine concentration. Overall, 10.9% of the study population had low iron; 32.2 and 18.8% had low or high iodine levels, respectively. Compared with normal levels of iron and iodine, normal iron and high iodine were associated with reduced free T3 and increased risk of abnormal high TSH. Combined low iron and low iodine was associated with reduced free T3 and increased TSH. In addition, high iodine was associated with increased risk of abnormal high TSH in females but not in males. Thyroid function may be disrupted by low levels of iron or abnormal iodine, and relationships are complex and sex-specific. Large prospective studies are needed to understand the mechanisms by which iron interacts with iodine on thyroid function.     

Oxidative Effects of Iron on Erythrocytes

In this work we have investigated the effects of iron-induced free radical formation in normal human erythrocytes in vitro, as a model system for studying iron damage, and in erythrocytes from patients with β-thalassaemia major. The resulting oxidative effects were measured in terms of methaemoglobin formation and reduced glutathione loss. The effects of desferrioxamine, an iron-chelating agent, were also investigated.

The results show that the increased methaemoglobin formation after iron-induced oxidative stress is consistent with a decline in the intracellular glutathione levels and that this process is inhibited by desferrioxamine. Similar treatment of red cell haemolysates produces less methaemoglobin. This suggests that, on exposure of intact erythrocytes to iron-induced free radical effects, the red cell membrane exacerbates the breakdown of the antioxidant defences of the cell and the oxidation of haemoglobin.     

Iron uptake and metabolism by hepatocytes

The hepatocytes form part of the iron storage system of the body. In serving this function they exchange iron bidirectionally with the plasma iron transport protein transferrin (Tf). Iron uptake involves binding of the iron-Tf complex to cell membrane receptors and endocytosis into low-density vesicles, where the iron is released from its carrier protein before the Tf is returned undegraded to the extracellular medium. Two components of the iron uptake process can be distinguished, one saturable at low concentrations of diferric Tf and the other not saturable by increasing the Tf concentration. Both result in net uptake of iron by the cells and both appear to depend on specific binding to the cell membrane and endocytosis. Hepatocytes also obtain some iron from haptoglobin-hemoglobin, heme-hemopexin, and ferritin (Fn), in each case by interaction with membrane receptors and endocytosis. Within the cell iron from all sources enters one or more transit pools, where it is available for exchange with the iron storage protein Fn, and for release from the cell to plasma Tf or to iron chelators administered therapeutically or experimentally. Chelator-mediated iron release occurs to the plasma and/or to the bile, depending on the nature of the chelator and the source of the iron.     

Iron in granulocytes of nephrotic patients determined by Zeeman electrothermal atomic absorption spectrophotometry

One of the major threats to patients undergoing maintenance hemodialysis is an increased susceptibility to infections caused by microorganisms, among whichYersinia orListeria are frequently recovered. In patients receiving hemodialysis, iron overload owing to multiple transfusions plays an important role in the mechanisms underlying the susceptibility to bacterial infections, partially mediated by impaired neutrophil function. In order to assess the true role of iron at the cellular level, an AAS method was developed to measure the iron content of granulocytes. Iron levels in the granulocytes were determined in an apparently healthy population and in a population of iron-overloaded renal hemodialysis patients. Granulocytes were isolated by a method modified from Böyum. The analyses were performed using pyrocoated graphite tubes, and in one of the char steps, oxygen was used to facilitate ashing. The mean iron level found in the granulocytes from apparently normal persons was 4.07 fg/cell (n=17) with a CV of 44%; the mean value for the dialysis patient group was 4.59 fg/cell (n=8) with a CV of 37%. There was no significant difference between the two groups,p=0.70.     

Spleen size in chronic renal failure.

To investigate the cause of clinically detectable splenomegaly, which is common in patients receiving regular haemodialysis, splenic volume was assessed by isotopic scanning using intravenously injected technetium-99m microspheres in 34 controls and 149 patients with chronic renal failure. Of the patients, 16 had never received dialysis, 10 were undergoing continuous peritoneal dialysis, 94 were undergoing regular haemodialysis, and 29 had undergone successful renal transplantation more than nine months previously. Mean splenic volume was increased only in the patients who were receiving haemodialysis. Splenic enlargement was probably not due to iron overload as it occurred in all patients who had received haemodialysis, 14 of whom had not received intravenous iron. No patient had had hepatitis. Splenic enlargement was probably related to the process of haemodialysis itself and may have been due either to red cell damage produced by haemodialysis or to an immunological reaction induced by a component of haemodialysis, possibly ethylene oxide.     

Iron Supplementation Decreases Severity of Allergic Inflammation in Murine Lung

The incidence and severity of allergic asthma have increased over the last century, particularly in the United States and other developed countries. This time frame was characterized by marked environmental changes, including enhanced hygiene, decreased pathogen exposure, increased exposure to inhaled pollutants, and changes in diet. Although iron is well-known to participate in critical biologic processes such as oxygen transport, energy generation, and host defense, iron deficiency remains common in the United States and world-wide. The purpose of these studies was to determine how dietary iron supplementation affected the severity of allergic inflammation in the lungs, using a classic model of IgE-mediated allergy in mice. Results showed that mice fed an iron-supplemented diet had markedly decreased allergen-induced airway hyperreactivity, eosinophil infiltration, and production of pro-inflammatory cytokines, compared with control mice on an unsupplemented diet that generated mild iron deficiency but not anemia. In vitro, iron supplementation decreased mast cell granule content, IgE-triggered degranulation, and production of pro-inflammatory cytokines post-degranulation. Taken together, these studies show that iron supplementation can decrease the severity of allergic inflammation in the lung, potentially via multiple mechanisms that affect mast cell activity. Further studies are indicated to determine the potential of iron supplementation to modulate the clinical severity of allergic diseases in humans.