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PubMedDate not supplied

[Formation of iron complexes with ascorbic acid in physiological conditions in vitro and in tissue in vivo].

Rapid dissociated Fe(III)-ascorbic acid complexes are formed after the mixing of Fe(II) (100 mkM) with ascorbic acid (1 mM) at pH-7,4. As a result of these complexes formation Fe(II) concentration was decreased in solution, but o-phenantrolin addition or pH decreased up to 6.1 lead to the destruction of these complexes and reduction of iron up to Fe(II). Iron-ascorbic acid paramagnetic complexes were not observed in the perfused rat liver homogenate. Probably, these facts were due to the presence of other stronger reductants in the tissue.

Animals↗
PubMed1989

Transfer RNA is cleaved by activated bleomycin.

Activated bleomycin is shown for the first time to cleave tRNA in a specific and dose-dependent manner. Adenine and uracil are released in the reaction. Bleomycin and Fe(III)-bleomycin bind to yeast tRNAPhe) in analogy with the known behavior of the drug with B-DNA.

Bleomycin↗
PubMed1989

Mössbauer and EPR studies of the binuclear iron center in ribonucleotide reductase from Escherichia coli. A new iron-to-protein stoichiometry.

57Fe-enriched ribonucleotide reductase subunit B2 from Escherichia coli strain N6405/pSPS2 has been characterized by Mössbauer and EPR spectroscopy in its native diferric state and in a new differous form. The native protein exhibits two Mössbauer doublets in a 1:1 ratio with parameters that are in excellent agreement with those reported for the wild-type protein (Atkin, C. L., Thelander, L., Reichard, P., and Lang, G. (1983) J. Biol. Chem. 248, 7464-7472); in addition, our studies show the absence of adventitiously bound iron. The iron content in the present samples approached 4 per B2 subunit, and the tyrosyl radical content exceeded 1 per B2 subunit. The higher values are attributed to the use of a new epsilon 280 for the protein and more efficient methods for iron extraction. We thus propose that subunit B2 has two binuclear iron clusters, each associated with its own tyrosyl radical, in contradistinction from the prevailing model. Reduction of the native protein with dithionite or reconstitution of the apoprotein with Fe(II) afforded a protein complex with Mössbauer parameters, delta EQ = 3.13 mm/s and delta = 1.26 mm/s at 4.2 K, and a low field EPR signal associated with an integer spin system. These spectral properties resemble those of methane monooxygenase in its diferrous form. Upon exposure to O2, the reduced subunit B2 readily converts to the diferric state and yields active enzyme.

Dithionite↗
PubMed1987

The requirement for iron (III) in the initiation of lipid peroxidation by iron (II) and hydrogen peroxide.

The initiation of lipid peroxidation by Fe2+ and H2O2 (Fenton's reagent) is often proposed to be mediated by the highly reactive hydroxyl radical. Using Fe2+, H2O2, and phospholipid liposomes as a model system, we have found that lipid peroxidation, as assessed by malondialdehyde formation, is not initiated by the hydroxyl radical, but rather requires Fe3+ and Fe2+. EPR spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide and the bleaching of para-nitrosodimethylaniline confirmed the generation of the hydroxyl radical in this system. Accordingly, catalase and the hydroxyl radical scavengers mannitol and benzoate efficiently inhibited the generation and the detection of hydroxyl radical. However, catalase, mannitol, and benzoate could either stimulate or inhibit lipid peroxidation. These unusual effects were found to be consistent with their ability to modulate the extent of Fe2+ oxidation by H2O2 and demonstrated that lipid peroxidation depends on the Fe3+:Fe2+ ratio, maximal initial rates occurring at 1:1. These studies suggest that the initiation of liposomal peroxidation by Fe2+ and H2O2 is mediated by an oxidant which requires both Fe3+ and Fe2+ and that the rate of the reaction is determined by the absolute Fe3+:Fe2+ ratio.

Animals↗
PubMed1978

Magnetic circular dichroism approach to hemoprotein analyses.

Accumulative magnetic circular dichroism (MCD) spectra have shown that MCD is indispensable in exploring the structures and electronic states of hemoproteins. Theoretical and instrumental introductions of MCD spectroscopy were followed by a specific theoretical treatment for applying MCD to various oxidation, ligand, and spin states of hemoproteins. By including explicit electronic states of the heme iron, the theory can systematically interpret the MCD results of various states of hemoproteins. The MCD spectra of myoglobin derivatives offered a typical example for various states of hemoproteins. As an MCD application to heme enzymes, MCD studies on cytochrome P-450 were described in detail, and other extensive applications of MCD to various hemoproteins were cited.

Chemical Phenomena↗
PubMed1987

Bioavailability and therapeutic efficacy of bivalent and trivalent iron preparations.

The bioavailability of iron on Fe(III)-hydroxide-polymaltose complex was compared intraindividually with that of Fe (II)-ascorbate (iron absorption) and a Fe (II)-sulphate quick release preparation (haemoglobin regeneration test). The study was carried out in a population of 16 healthy male volunteers, phlebotomized in weekly intervals until development of an iron deficiency anaemia in order to establish a test population with only small variations of their individual body iron status. Intestinal iron absorption in fasting state as measured by 59Fe whole body retention and simultaneous estimation from plasma iron tolerance curves was low for the 59Fe (III)-complex (1.2 +/- 0.1% (means +/- SD] as compared to the 59Fe (II)-ascorbate (43.7 +/- 7.1% (means +/- SD]. Iron administration together with a test meal did not affect the absorption from the 59Fe (II)-ascorbate, whereas the 59Fe (III)-complex showed a significant increase in absorption (8.8 +/- 4.7% (means +/- SD]. Haemoglobin (Hb) regeneration after 100 mg of iron as Fe (III)-complex and Fe (II)-sulphate administered during 28 days with meals amounted to a mean of 0.68 +/- 0.2 g/l and 1.1 +/- 0.3 g/l (means +/- SD) of total daily Hb-increase and a net-Hb-increase of 0.31 +/- 0.37 g/l and 0.79 +/- 0.36 g/l (means +/- SD), respectively. There was also a small but significant rise in serum ferritin during the oral treatment in both treatment groups. The results of Hb-regeneration after treatment with the Fe (III)-complex were in the range which could be expected from the absorption measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Transferrin subtypes in the Polish population.

Transferrin subtypes were determined by isoelectric focusing on a thin-layer polyacrylamide gel, using a mixture of ampholine of three pH ranges. In a sample of the Polish population numbering 361 subjects, six Tf subtypes dependent on three alleles Tfcc1, Tfcc2, Tfcc3 were encountered. They occurred with the following frequency: 0.744, 0.212, 0.044. It was found that Tf system in the Polish population was in a good agreement with Hardy Weinberg equilibrium.

Adult↗
PubMed1979

[Comparison of bio-availability, antianaemic efficacy, tolerance and drug costs in oral iron(II) and iron(III) preparations (author's transl)].

In addition to a clinical study which investigated the bio-availability of three oral iron preparations S, L and X by using postabsorption serum iron concentration curves, the same drugs were compared in order to study their antianaemic efficacy, tolerance and drug costs arising during and iron therapy. Moreover, these iron drugs were related to other current clinical reports. Within all three iron preparations a very good correlation was found between bio-availability and haematopoietic efficacy: The very good absorbability of the bivalent quick release stick capsule preparation S (= 100%) corresponded with a very good capacity of haemoglobin regeneration (2,6 +/- 0,4 g Hb/1/day) whereas due to a very low absorbability (10% to 16%) the antianaemic efficacy of both iron(III) preparations L and X had to be rated as moderate to predominantly poor. In normal therapeutic dosis all three iron preparations showed no differences in tolerance. The ratio of side effects was similar to that after ingestion of placebo. In comparing the drug costs during a therapy leading to a real absorption of 1 g of iron the most effective iron(II)sulfate preparation S is 3.6 to 12.6 times cheaper than the compared trivalent preparations L and X. Therefore, there is no justification for the further production or introduction on the market of trivalent iron preparations.

Absorption↗
PubMed1985

Technique of labeling monocytes with 111In-Fe colloid for use in humans.

In order to follow monocyte kinetics in hematologic malignancies by means of radioactive labeling, three conditions are necessary: (a) no loss of monocytes during separation, (b) specific labeling of monocytes, and (c) normal functional capacities of the labeled monocytes. In this report a method is described that fulfills the first two conditions and can be executed with maintenance of sterility. Cell labeling was performed using a mononuclear cell suspension consisting of monocytes (20%-50%), lymphocytes (50%-80%), and with minor contamination by granulocytes, thrombocytes, and erythrocytes. This cell suspension was obtained by centrifugation of a leukocyte suspension on a gradient of 16% wt/vol and 22% wt/vol human serum albumin solutions. The recovery of monocytes with this enrichment method approached 100%. Monocytes were labeled by endocytosis of 111In-Fe colloid; monocytes were labeled significantly higher than lymphocytes (P less than 0.001) and granulocytes (P less than 0.01) (Wilcoxon's two-sample test). Cell viability after labeling was greater than 90%.

Autoradiography↗
PubMed1979

Enhancement of the chromosome-damaging action of ascorbate by transition metals.

Freshly prepared ascorbate inhibited mitosis and induced chromosome aberrations in cultured Chinese hamster ovary cells. Cu(II) and Mn(II) (10(-4) or 10(-5) M) enhanced both actions. Fe(II) and Fe(III) (10(-4) or 10(-5) M) reduced or abolished the mitosis-inhibiting action of ascorbate. At 10(-4) M, Fe(II) and Fe(III) strongly enhanced the chromosome-damaging capacity of ascorbate. Up to 100% of all examined metaphase plates had multiple chromosome exchanges or breaks. Since the cytostatic and clastogenic effect of ascorbate of H2O2 to induce chromosome aberrations was examined. H2O2 and a H2O2: Fe(II) mixture (Fenton reagent) induced chromosome breaks and exchanges but to a lesser degree than did ascorbate: Cu(II), Mn(II), Fe(II), or Fe(III) mixtures. Whether the strong chromosome damaging capacity of ascorbate plus transition metals as seen in the in vitro test system poses a health hazard only properly designed in vivo studies can reveal.

Animals↗
PubMed1979

Influence of superoxide generating system, vitamin E, and superoxide dismutase on radiation consequences.

During studies of the mechanism by which hemolysis is induced in irradiated human erythrocytes in vitro, several inducements of membrane lipid peroxidation and protective effects of vitamin E (V.E) and superoxide dismutase (SOD) were investigated. Findings were: (1) Before hemolysis, K+ release from erythrocytes induced by radiation stimulated hemolysis but was inhibited by V.E or SOD. (2) Lipid peroxidation of mitochondria induced by Fe3+, ADP, and superoxide (O2-) generating system, and lipid peroxidation of microsome induced by O2- generating system, were also inhibited by V.E or SOD. (3) X-ray or 60Co gamma-ray radiation stimulated lipid peroxidation of liver homogenate, microsome, and liposome. Some of this peroxidation was inhibited by V.E. or SOD. These results suggest that O2- and/or OH formation by radiation induces membrane lipid peroxidation, which causes deterioration of membrane resulting in change of ion permeability and consequent hemolysis.

Adenosine Diphosphate↗
PubMedDate not supplied

Certain phosphate compounds in the erythrocytes of patients with primary hyperlipidaemia.

The investigations were carried out in 30 patients with primary hyperlipidaemia (hypercholesterolaemia, hypertriglyceridaemia and mixed form). The serum total cholesterol and triglycerides, and in the erythrocytes the levels of AMP, ADP, ATP, ATP complex with Fe, MP, HDP and DGP were determined. Twenty blood donors served as a control group. The obtained results showed a statistically highly significant rise in ADP concentration in all investigated subgroups of hyperlipidaemic subjects, and a non-significant quantitative shift of other determined phosphate compounds.

Adenosine Diphosphate↗
PubMed1984

Evidence for a role of hydroxyl radical in immune-complex-induced vasculitis.

Previously it was shown that tissue injury occurring in acute immune-complex-induced vasculitis, which is complement and neutrophil-dependent, is significantly attenuated by the presence of catalase, suggesting the pathogenic role of H2O2 generated from activated neutrophils. We now show that significant protection is also afforded by pretreatment of animals with apolactoferrin , a naturally occurring chelator of iron. Iron-saturated lactoferrin is devoid of protective effects. Deferoxamine mesylate, a synthetic iron chelator, also has protective effects. Infusion of ionic iron, especially Fe(III), potentiates the tissue injury. Significant protection from tissue injury is also produced by treatment of rats with dimethyl sulfoxide, a potent hydroxyl radical scavenger. Morphologically, animals treated with these protective interventions show the influx of neutrophils into sites of immune complex deposition, but there is markedly attenuated edema, little or no hemorrhage, and little evidence of endothelial cell injury, in contrast to the findings in nonprotected animals. These data support the suggestion that immune-complex-induced injury may be linked to generation of H2O2 from activated neutrophils and the subsequent conversion of H2O2 to the hydroxyl radical.

Animals↗
PubMed1982

The mechanism of phenylalanine hydroxylase.

The site of oxygen binding during phenylalanine hydroxylase (PAH)-catalyzed turnover of phenylalanine to tyrosine has been tentatively identified as the 4a position of the tetrahydropterin cofactor, based on the spectral characteristics of an intermediate generated from both 6-methyltetrahydropterin and tetrahydrobiopterin during turnover. The rates of appearance of the intermediate and tyrosine are equal. Both rates exhibit the same dependence on enzyme concentration. PAH also requires 1.0 iron per 50,000-dalton subunit for maximal activity. A direct correlation between iron content and specific activity has been demonstrated. Apoenzyme can be reactivated by addition of Fe(II) aerobically or Fe(III) anaerobically and can be repurified to give apparently native protein. Evidence from electron paramagnetic resonance implicates the presence of high spin (5/2) Fe(III). As a working hypothesis we postulate that a key complex at the active site may be one containing iron in close proximity to a 4a-peroxytetrahydropterin.

Apoenzymes↗