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At least 19 recordsLinked to original sources

PubMed1976

[Comparison of the metabolism of 2 injectable iron preparations (sorbitol iron and polymaltose iron) with the metabolism of transferrin and hemoglobin iron].

Iron distribution in the different organs and chemical compartments of the rat has been studied after intravenous injection of 59Fe-sorbitol (Jectofer-Astra) and 59Fe-polymaltose (Fer Hausmann Lucien) and compared with the metabolism of 59Fe bound to transferrin and to hemoglobin. Both parenteral iron preparations are utilized more slowly than Iron-transferrin. The speed of red cell incorporation of 59Fe from sorbitol is similar to the hemoglobin iron utilization (half incorporation in red cells: 4 to 5 days). Iron polymaltose is much more slowly utilized (half incorporation in the red cells: 13 to 15 days). One third of the 59Fe from sorbitol is eliminated in urine, the remaining iron being taken up to 60% by the liver and to 30% by the bone marrow. It is very quickly catabolized, since as early as the first hour after injection most of the 59Fe is bound to polymaltose till the 14th day. Between the third and fourth week 25% of the 59Fe from polymaltose is found in hemosiderin. These metabolic differences are also found in man: 59Fe from iron sorbitol is found in urine after injection, is mobilized by desferrioxamine after six days, and eliminated through dialysis membranes. On the other hand the 59Fe from polymaltose is slowly but completely utilized and not mobilized by desferrioxamine in the first week after injection. The data give the indications for use and the pharmacokinetics of two forms of parenteral iron and oral preparations in the treatment of iron deficiency.

Animals↗

PubMed1975

Bioavailability of trivalent iron in oral iron preparations. Therapeutic efficacy and iron absorption from simple ferric compounds and high- or low-molecular weight ferric hydroxide-carbohydrate complexes.

All available results from critical hemoglobin regeneration tests, postabsorption serum iron concentration studies, 59Fe erythrocyte incorporation and 59Fe whole-body retention measurements demonstrate that humans do absorb ferrous iron between 4 and 10 times (in the average about 5 times) better than ferric iron from therapeutic oral 50--250 mg iron doses. Ferrous sulfate iron is 3 to 4 times better available than the iron from ferric ammonium citrate or sulfate. Whereas 100 mg of ferrous sulfate iron/day are sufficient for an optimal oral compensation iron therapy and to produce initial hemoglobin regeneration rates of about 0.26 g/100 ml/day, 400 to 1000 mg of ferric iron/day are necessary for the same therapeutic effect because of the poor bioavailability of ferric iron. The ratio of the dose-absorption relationships for ferric and ferrous 59Fe was shown to decrease from 0.43 for a diagnostic 0.56 mg Fe dose to 0.21 for the therapeutic 50 mg Fe dose in subjects with normal iron stores. Absorption ratios of 0.65 for the 0.56 mg Fe dose and 0.26 for the 50 mg Fe dose were measured in subjects with depleted iron stores. At all dose levels the superior bioavailability of ferrous iron was demonstrable. A high-molecular weight ferric hydroxide-carbohydrate complex (MW similar to 30 000) was palatable but so poorly absorbed that is was practically without effect on hemoglobin regeneration even at a daily 300 mg Fe dose. Following several warnings such a useless commerecial oral iron preparation was finally withdrawn from the market. The iron from any high-molecular weight carbohydrate complex of ferric hydroxide has to be suspected to be poorly absorbed and therefore therapeutical useless, unless the opposite has been demonstrated with a reliable bioassay (59Fe absorption whole-body retention and hemoglobin regeneration test). A low-molecular weight so-called ferric hydroxide-fructose complex was shown to contain iron of more or less the same poor bioavailability as contained in ferric chloride since the iron from ferrous sulfate was about 5 times better absorable. The good absorption of ferrous sulfate iron was not further augmented by even very large oral doses of fructose since this carbohydrate did not improve the ferrous iron absorption at a fructose: Fe molar ratio of 106:1. Trivalent iron in simple compounds like ferric ammonium citrate or in low- and high-molecular weight carbohydrate complexes of ferric hydroxide is so poorly available for intestinal iron absorption in man that it cannot be used for a fast and reliable oral iron therapy with reasonably low doses as it can be easily practised with quick-lease preparations of ferrous sulfate at a 100 mg Fe2

Anemia, Hypochromic↗

PubMed1992

Deferoxamine-induced iron mobilization and redistribution of myocardial iron in cultured rat heart cells: studies of the chelatable iron pool by electron microscopy and Mössbauer spectroscopy.

Iron mobilization by deferoxamine from iron-loaded rat heart cells in culture was studied by electron microscopy and Mössbauer spectroscopy to identify the chelatable iron pool. Studies in which iron 59 was used have shown a diminishing response to deferoxamine with increasing time intervals, which suggests a gradual transit from a more available to a less available storage iron compartment. Mössbauer spectroscopy showed that practically all iron mobilized by deferoxamine was derived from the small (less than 3.0 nm) recently acquired iron particles, which supports the "last-in, first-out" principle. Quantitation of cytosolic ferritin iron particles has shown a highly reproducible increase in cytosolic ferritin iron after deferoxamine treatment. This intracellular redistribution of iron stores is explained either by a reduced transfer of cytosolic ferritin into siderosomes or, more likely, by increased mobilization of membrane-bound iron deposits from insoluble polynuclear iron complexes in siderosomes and their subsequent incorporation into cytosolic ferritin. Thus the protective effect of deferoxamine on iron-loaded heart cells may be twofold: (1) net removal of excess iron by the formation of a stable complex of iron with deferoxamine and its secretion into the extracellular environment and (2) a shift of solubilized iron from membrane-bound deposits into the cytosol where iron is detoxified by its incorporation into the hollow shell of the ferritin protein.

Animals↗

PubMed1991

Mutational analysis of the mitochondrial Rieske iron-sulfur protein of Saccharomyces cerevisiae. III. Import, protease processing, and assembly into the cytochrome bc1 complex of iron-sulfur protein lacking the iron-sulfur cluster.

We have used site-directed mutagenesis of the Saccharomyces cerevisiae Rieske iron-sulfur protein gene (RIP 1) to convert cysteines 159, 164, 178, and 180 to serines, and to convert histidines 161 and 181 to arginines. These 4 cysteines and 2 histidines are conserved in all Rieske proteins sequenced to date, and 4 of these 6 residues are thought to ligate the iron-sulfur cluster to the apoprotein. We have also converted histidine 184 to arginine. This histidine is conserved only in respiring organisms. The site-directed mutations of the six fully conserved putative iron-sulfur cluster ligands result in an inactive iron-sulfur protein, lacking iron-sulfur cluster, and failure of the yeast to grow on nonfermentable carbon sources. In contrast, when histidine 184 is replaced by arginine, the iron-sulfur cluster is assembled properly and the yeast grow on nonfermentable carbon sources. The site-directed mutations of the 6 fully conserved residues do not prevent post-translational import of iron-sulfur protein precursor into mitochondria, nor do the mutations prevent processing of iron-sulfur protein precursor to mature size protein by mitochondrial proteases. Optical spectra of mitochondria from the six mutants indicate that cytochrome b is normal, in contrast to the deranged spectrum of cytochrome b which results when the iron-sulfur protein gene is deleted. In addition, mature size iron-sulfur apoprotein is associated with cytochrome bc1 complex purified from a site-directed mutant in which iron-sulfur cluster is not inserted. These results indicate that mature size iron-sulfur apoprotein, lacking iron-sulfur cluster, is inserted into the cytochrome bc1 complex, where it interacts with and preserves the optical properties of cytochrome b. Insertion of the iron-sulfur cluster is not an obligatory prerequisite to processing of the protein to its final size. Either the processing protease cannot distinguish between iron-sulfur protein with or without the iron-sulfur cluster, or insertion of the iron-sulfur cluster occurs after the protein is processed to its mature size, possibly after it is assembled in the cytochrome bc1 complex.

Amino Acid Sequence↗

PubMed1992

Salivary iron status in children with iron deficiency and iron overload.

Forty anaemic (iron deficiency anaemia-27, thalassemia major-8, and aplastic anaemia-5) and 10 non-anaemic children (serving as controls) aged from 8 months to 10 years were selected for the study. The salivary iron was significantly higher in iron deficient and iron overload conditions compared to controls. The mean salivary:serum iron ratio was same in control and iron overload cases, while it was twice as high in iron deficient anaemic children. The correlation between salivary iron and serum iron was significant (r = 0.7392, P less than 0.001) in these cases. The iron deficient anaemic children with hypoalbuminaemia had significantly reduced serum and salivary protein (P less than 0.001), but iron concentrations in serum and saliva remained unaltered. The salivary protein level had significant correlations with serum albumin and serum protein (P less than 0.001). Thus, the iron in saliva is maintained at a higher level and more so in iron deficiency anaemia; it correlates well with serum iron (r = 0.6853, P less than 0.001) in iron deficient anaemic children also and is not affected by co-existing hypoproteinaemic situation.

Albumins↗

PubMed1992

Regulation of iron absorption in iron loaded subjects with end stage renal disease: effects of treatment with recombinant human erythropoietin and reduction of iron stores.

The effects on iron absorption of variation in erythroid activity, haemoglobin and iron stores were studied in six anaemic dialysis-dependent subjects in whom iron stores were increased from previous red cell transfusions. Gastrointestinal mucosal uptake and whole body retention of oral iron were measured at the beginning of the study, after starting treatment with recombinant erythropoietin (but before significant increase in haemoglobin), after partial correction of anaemia, after further reduction of iron stores by repeated phlebotomy, and when erythropoiesis decreased from the discontinuation of treatment with erythropoietin. Between successive measurements, valid comparisons were made in five subjects. Correction of anaemia decreased whole body retention of iron through decreased mucosal uptake (P = 0.032). Further reduction in iron stores through repeated phlebotomy whilst the increase in haemoglobin was maintained by treatment with erythropoietin, tended to increase whole body retention of iron through an increase in mucosal transfer (P = 0.010). With initial enhancement of erythropoiesis in anaemic iron-loaded subjects there was no change in any measured component of iron absorption. However, after correction of anaemia and reduction of iron stores, a decrease in erythropoiesis was associated with decreased whole body iron retention in all subjects through decreased mucosal transfer (P = 0.028). The data suggest that anaemia upregulates mucosal iron uptake, and that erythroid activity upregulates mucosal transfer but that this latter effect may be counter-balanced by iron overload which downregulates mucosal transfer.

Adult↗

PubMed1979

Iron and the liver: subcellular distribution of iron and decreased microsomal cytochrome P-450 in livers of iron-loaded rats.

To understand better the intracellular iron distribution and metabolic consequences of chronic hepatic iron overload, rats were given large doses of iron dextran or ferric citrate intraperitoneally. They accumulated large quantities of iron within Kupffer cells and hepatocytes. The relative subcellular iron distributions were similar in controls and iron-loaded rats, despite a ten- to 20-fold difference in hepatic iron concentration. Electron microscopy of whole liver and subcellular particulate fractions suggested that iron was present in highest concentration in lysosomes, which were rendered more labile by its presence. Nevertheless, quantitative iron determinations on all subcellular fractions, obtained by two preparative methods, showed that most of the iron was present in the "soluble" fraction. The amount of iron in the "microsomal" fraction varied, depending on the techniques used for preparation of this fraction. Cytochrome P-450 and total heme concentrations were decreased 40% to 50% in microsomes isolated from iron-loaded livers.

Animals↗

PubMed1992

Iron absorption from chewable vitamins with iron versus iron tablets: implications for toxicity.

The medical literature contains few, if any, reports of severe iron (Fe) poisonings from ingestion of chewable multivitamins with iron. One possible explanation for this observation is that iron from multivitamins is more poorly absorbed than iron from iron tablets. To compare iron absorption from multivitamins with iron absorption from ferrous fumarate tablets, male adult volunteers were given 6 mg of elemental Fe/kg body weight as chewable multivitamins with iron or as crushed ferrous fumarate tablets in a crossover study. Serum Fe and total iron binding capacity (TIBC) were determined prior to administration of the tablets and one, two, four, and six hours after ingestion. Statistical analyses demonstrated increased and more rapid absorption of Fe from the multivitamin preparation. These results suggest that iron is well absorbed from chewable multivitamins with iron and should theoretically have the potential for producing serious toxicity when taken in overdose. The reasons that such toxicity is not commonly seen clinically are discussed, and a plan for further investigation of this issue is proposed.

Adult↗

PubMed1975

Iron absorption in early pregnancy - a study of the absorption of non-haeme iron and ferrous iron in early pregnancy.

The absorption of non-haeme iron in the food and from a 3 mg reference dose of ferrous iron in solution was measured in 17 healthy women before the 12th week of gestation and in 13 of the women two months after legal abortion. The absorption of ferrous iron in solution was calculated from determinations of the 55Fe activity in blood samples. The food iron absorption was measured from 59Fe-labelled test meals using a highly sensitive whole-body counter. In addition bone-marrow smears and other haematological parameters were studied. The median value of the absorption from the non-haeme food iron was 2.5% and from the ferrous iron salt 10.0 % in early pregnancy in women with storage iron. Two months after abortion the absorption increased to 12.6 and 42.6 % respectively. In early pregnancy the absorption of iron was higher in women without stainable iron in bone-marrow smears. The present results confirm previous observations that the absorption of food iron in early pregnancy is lower than the basal daily requirements. The low absorption is only partly explained by the reduced requirements of iron in early pregnancy. Some other factors related to pregnancy seem also to be involved.

Abortion, Induced↗

PubMed1979

Preparation and partial characterization of iron-sulfur, iron-selenium, and iron-tellurium complexes of bovine serum albumin.

An artificial Fe-S* protein was prepared by the reaction of bovine serum albumin with FeSO4 and Na2S or with a synthetic Fe-S*-1,4-butanenedithiol complex. These improved methods enabled us to characterize the derivatives from serum albumin. The Fe-S* albumin complex has about 20 iron ions and 14 labile sulfur atoms per molecule of the protein, whose absorption spectrum closely resembled that of 2Fe-2S* proteins. Its electron paramagnetic resonance spectrum exhibited signals different from those of ferredoxins. The addition of p-chloromercuriphenylsulfonate quenched the optical absorption in the visible region as well as the electron paramagnetic resonance signals. These properties of the albumin-iron complex are similar to those of iron-sulfur dithiothreitol and mercaptoethanol complexes, suggesting that the albumin-iron complex has one or more protein ligands besides sulfur lignads. Presumably, the oxygen atom of the tyrosine residue, or other hydroxyamino acids participates in the complex formation. In this context, the albumin polypeptide appears to be incapable of forming an iron-sulfur cluster identical to those of ferredoxins. Yet, from the albumin-iron derivative, the extrusion of the iron-sulfur core with benzenethiol provided products similar to those from ferredoxins. The iron-selenium and iron-tellurium derivatives of the bovine serum albumin were prepared and partially characterized by optical absorption and electron paramagnetic resonsnace spectroscopies. These results imply that both selenium and tellurium can be incorporated into the protein molecule as the respective labile components.

Chemical Phenomena↗

PubMed1976

Iron deficiency in an Eskimo village. The value of serum ferritin in assessing iron nutrition before and after a three-month period of iron supplementation.

The serum ferritin concentration, a new means of assessing iron nutrition, was utilized in conjunction with the hematocrit value, serum iron concentration, and total iron binding capacity to determine the effect of a three-month period of iron supplementation in a group of 146 Eskimo children in Chevak, Alaska. Before treatment, 41% of the children had concentrations of serum ferritin below normal, 18% had a subnormal serum transferrin saturation, and 26% were anemic. After supplementation, only 6% had a subnormal serum ferritin concentration. Despite this evidence of improved iron stores in the group as a whole, the prevalence of low serum transferrin saturation and of anemia remained high, 15% and 17%, respectively. These results could be explained by a high incidence of infection, which, like iron deficiency, is associated with anemia and a low serum transferrin saturation. We conclude that the serum ferritin determination reflected an improvement in iron nutrition that was not as readily apparent by other measurements, and that factors other than iron deficiency also played an important role in the mild anemia that was prevalent in Chevak.

Adolescent↗

PubMed1977

Iron-poly (sorbitol-gluconic acid) complex and iron-dextran in the treatment of severe iron deficiency anaemia.

An investigation has been carried out to study the efficacy of iron-poly (sorbitol-gluconic acid) complex (Ferastral) in the treatment of iron deficiency anaemia. Ferastral was given by the intramuscular route every second or third day in a dose of 500 mg, divided in two injections. These were compared with the results of a group treated with iron-dextran given by Total Dose Infusion (TDI). A total of 38 patients were treated with either Ferastral or iron-dextran by TDI, respectively, given according to random allocation. The total dose of iron given in both groups was 1 500 mg of elemental iron. The parameters investigated were haematocrit and haemoglobin. Side-effects were also recorded. The results in the group treated with Ferastral where the mean initial haemoglobin value was 9.5 g/100 ml showed a mean haemoglobin increase to 13.2 g/100 ml after eight weeks. Initial haemoglobin values and haemoglobin increase for iron-dextran by TDI were quite similar. Three patients in the Ferastral group had transient discolouration at the site of injection and one patient in the iron-dextran TDI-group had a serious allergic reaction.

Anemia, Hypochromic↗

PubMed1991

Effects of calcium on hepatocyte iron uptake from transferrin, iron-pyrophosphate and iron-ascorbate.

Calcium stimulates hepatocyte iron uptake from transferrin, ferric-iron-pyrophosphate and ferrous-iron-ascorbate. Maximal stimulation of iron uptake is observed at 1-1.5 mM of extra-cellular calcium and the effect is reversible and immediate. Neither the receptor affinity for transferrin, nor the total amounts of transferrin associated with the cells or the rate of transferrin endocytosis are significantly affected by calcium. In the presence of calcium the rate of iron uptake of non-transferrin bound iron increases abruptly at approximate 17 degrees C and 27 degrees C and as assessed by Arrhenius plots, the activation energy is reduced in a calcium dependent manner at approx. 27 degrees C. At a similar temperature, i.e., between 25 degrees C and 28 degrees C, calcium increases the rates of cellular iron uptake from transferrin in a way that is not reflected in the rate of transferrin endocytosis. By the results of this study it is concluded that calcium increases iron transport across the plasma membrane by a mechanism dependent on membrane fluidity.

Animals↗

PubMed1977

Iron absorption in infants: high bioavailability of breast milk iron as indicated by the extrinsic tag method of iron absorption and by the concentration of serum ferritin.

Breast feeding is thought to result in a lower incidence of iron deficiency than does the use of unfortified cow milk forumalas, but there is scant documentation for this belief. The relationship of breast and cow milk feeding to absorption of iron and to iron status was investigated in a total of 45 term infants at about six months of age. Iron absorption was measured by total body counting. Laboratory assessment of iron status was based on the serum ferritin, hemoglobin, mean corpuscular volume, and transferrin saturation. The results indicated that infants fed breast milk during the entire first six to seven months of life attained greater iron stores than did those fed a cow milk formula. Breast-fed infants absorbed an average of 49% of a trace dose of extrinsic iron administered during a breast feeding in contrast to about 10% reported to be absorbed from cow milk under similar conditions. The data indicate that term infants who are breast fed may not require routine administration of supplemental iron.

Animals↗

PubMed1976

Absorption from different types of iron tablets - correlation between serum iron increase in total absorption of iron.

The absorption of iron from three different iron tablets - rapidly-disintegrating ferrous sulphate and ferrous carbonate tablets and slow-release ferrous sulphate tablets - was studied in healthy subjects with a serum iron technique and by whole-body counter measurements. A solution of ferrous sulphate was used as a reference. There were no differences in the absorption from the ferrous sulphate preparations, but the ferrous carbonate tablets were less well absorbed. Good correlation was found between the maximal serum iron response and the total absorption of iron and it was concluded that serum iron studies may be used for semiquantitative measurements of iron absorption in comparative studies on different iron preparations.

Adult↗

PubMed1979

Transferrin binding and iron transport in iron-deficient and iron-replete rat reticulocytes.

Three aspects of iron metabolism were studies in reticulocytes from iron-deficient, phlebotomized, and phenylhydrazine-treated rats: (1) the number of transferrin binding sites; (2) the uptake of 59Fe-transferrin; and (3) the ability of cytosol to mobilize 59Fe from 59Fe-labeled reticulocyte plasma membrane. The number of transferrin binding sites, assayed by measuring the binding of 125I-labeled transferrin to reticulocytes, were similar in iron-deficient and phlebotomy-induced reticulocytes, 66,000 and 75,000 binding sites/cell, respectively, but were about doubled, 120,000 binding sites/cell, in phenylhydrazine-induced reticulocytes. Uptake of 59Fe into iron-deficient reticulocytes was about one-half that for phlebotomy-induced reticulocytes and one-quarter that for phenylhydrazine-induced reticulocytes, the rates of uptake being measured as 21,540, 41,233, and 79,600 molecules of 59Fe per minute per cell, respectively. The mobilizing activity of cytosol free iron-deficient reticulocytes was also about one-half that of cytosol from phlebotomy-induced reticulocytes and about one-quarter that of cytosol from phenylhydrazine-induced reticulocytes. These results indicate that instead of a compensatory increase in these aspects of iron metabolism, the iron-deficient reticulocyte had a decreased ability to transport iron.

Anemia, Hypochromic↗

PubMed1977

Iron metabolism in Trypanosoma lewisi infection: serum iron and serum iron-binding capacity.

Progressive changes in iron levels, total iron binding capacity and hematocrit values in sera of rats infected with Trypanosoma lewisi are described. The host dietary group were: (1) complete or full complement; (2) iron-deficient, and (3) pair-fed or calorically restricted. The hematocrit values of T. lewisi-infected rats given the various diets were not significantly different from those of the controls. The decrease in total iron binding capacity (TIBC) of rats inoculated with T. lewisi and fed complete and pair-fed diets ranged up to 15% over uninfected controls. TIBC levels in rats fed an iron-deficient diet and inoculated with T. lewisi ranged up to 32% over uninfected controls. TIBC levels of deficient infected rats were significantly different from the controls from day 90 to infection to the end of the observation period. Serum iron (SI) values of non-infected rats regardless of dietary regimen showed significantly higher values than T. lewisi-infected animals between days 95 and 120. The average SI value, for this period, in adequately fed control rats was 204 +/- 7 microgram/100 ml as compared to 172 +/- 5 microgram/100 for trypanosome-infected rats. SI levels of rats on a pair-fed diet and infected with T. lewisi decreased to 17% over uninfected controls. SI levels of animals on an iron-deficient diet and infected with T. lewisi decreased up to 76% over uninfected controls.

Animals↗

PubMed1979

Normal serum iron and elevated total iron-binding capacity in iron-deficiency states.

Five nonanemic patients with normal erythrocytic indexes were found to have normal serum iron, elevated total iron-binding capacity, normal percentage of saturation of transferrin, and depleted bone marrow iron stores. These findings suggest that during the development of iron deficiency, an elevation of total iron-binding capacity occurs before the decrease of the serum iron. This may represent a compensatory mechanism to mobilize all traces of tissue iron to maintain normal erythropoiesis.

Adult↗