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At least 19 recordsLinked to original sources
PubMed1978

Iron uptake studies on erythroid cells.

Iron uptake from 55Fe-labelled transferrin, ferric citrate and the two fungal sideramines, ferricrocin and fusigen was studied using four erythroid cell cultures: Friend virus-transformed erythroleukemic cells (mouse), transformed bone marrow cells, Detroit-98 (human), reticulocytes (bovine), bone marrow cells (rabbit). The present comparative study reveals pronounced differences in iron uptake behaviour. Compared to transferrin, ferric citrate and the sideramines are preferred in transformed erythroid cells. In reticulocytes transferrin and ferric citrate showed a better uptake as compared to the two sideramines. Primary bone marrow cells showed nearly equal iron uptake rates using transferrin or ferricrocin.

Animals↗
PubMed1979

Radio-iron uptake of rat hepatoma.

Iron uptake rate of the tumor tissues of the rat liver was compared with that of the nontumor tissues of the same rat liver. Ferric[59Fe] citrate was injected to rats bearing hepatoma induced by the administration of diethylnitrosamine. The tumor and nontumor tissues were enucleated from the liver and radioactivity (cpm/10 mg tissue) of the individual tissue was calculated to estimate the iron uptake rate of the tissue. Eleven rats were finally available for the study. Population mean of radioactivity of the tumor group was larger than that of the nontumor group when examined 6 hr after the injection, so far as the specimens of both groups were sufficient in number, more than 19. The variance of radioactivity of the tumor group was always larger than that of the nontumor group, probably in part due to cytological and histological varieties of the tumor tissues. These results suggest that the tumor tissues can take up more iron than the nontumor tissues.

Animals↗
PubMed1975

Red cell iron uptake in hereditary microcytic anemia.

The iron uptake in vitro of red cells from mice with hereditary microcytic anemia (gene symbol mk) was studied to examine the hypothesis of a generalized impairment of cellular iron uptake in this conidition. Reticulocyte-rich red cells from anemic (mk/mk) and acutely bled normal (+/+) mice were incubated in 59Fe-labeled mouse plasma and the radioiron uptake measured. The 59Fe uptake of the mk/mk and +/+ cells was related in the same way to the reticulocyte concentration, the duration of incubation, and the percentage saturation of the plasma iron-binding capacity. However, under the same conditions, the iron uptake of red cells from normal (+/+) mice was greater than that by red cells from anemic (mk/mk) mice. Furthermore, the cellular loss of radioiron on exposure to EDTA was greater for the mk/mk red cells, although the proportion of the radioiron taken up that was incorporated into heme was the same for mk/mk and +/+ red cells. These results support the hypothesis of a generalized impairment of cellular iron uptake in hereditary microcytic anemia and suggest that there might be a defect in red cell receptor sites for transferrin in this condition.

Anemia↗
PubMed1978

The control of hepatic iron uptake: correlation with transferring synthesis.

The control of hepatic iron uptake was studied in the perfused liver isolated from rats subjected to nutritional iron deficiency. The total hepatic iron uptake and incorporation into ferritin was found to be higher in iron deficiency and during the 48 h of oral refeeding with iron than in the normal state. Specific incorporation of iron into feritin from a perfusate of normal transferrin iron saturation was enhanced in nutritional iron deficiency as compared to controls after 5 h of perfusion but not after 1 h, suggesting that increased uptake of iron from the perfusate may play a role in stimulating hepatic ferritin synthesis and assembly. This promotion of uptake into ferritin was inhibited by cycloheximide suggesting that enhanced incorporation of iron is dependent upon de novo synthesis of apoferritin. In control, nutritionally iron deficient and iron-refed rats there was a significant, direct correlation between the transferrin-iron saturation of the perfusate at physiological transferrin concentrations and total hepatic iron uptake after 5 h perfusion. A significant positive correlation was found between the hepatic total and ferritin iron uptake and the transferrin synthetic rate measured in the same liver. It is proposed that in the liver the negative feedback of iron supply on transferrin synthesis may be linked with a positive feedback on ferritin synthesis. The time-course of these reciprocal responses suggests a role for hepatic ferritin and/or a component of the non-haem, non-ferritin iron pool in the regulation of transferrin synthesis.

Animals↗
PubMed1976

Functional organization of the outer membrane of escherichia coli: phage and colicin receptors as components of iron uptake systems.

The functional interaction of outer membrane proteins of E. coli can be studied using phage and colicin receptors which are essential components of penetration systems. The uptake of ferric iron in the form of the ferrichrome complex requires the ton A and ton B functions in the outer membrane of E. coli. The ton A gene product is the receptor protein for phage T5 and is required together with the ton B function by the phages T1 and ø80 to infect cells and by colicin M and the antibiotic albomycin, a structural analogue of ferrichrome, to kill cells. The ton B function is necessary for the uptake of ferric iron complexed by citrate. Iron complexed by enterochelin is only transported in the presence of the ton B and feu functions. Cells which have lost the feu function are resistant to the colicins B, I or V while ton B mutants are resistant to all 3 colicins. The interaction of the ton A, ton B, and feu functions apparently permits quite different "substrates" to overcome the permeability barrier of the outer membrane. It was shown for ferrichrome dependent iron uptake that the complexing agent was not altered and could be used repeatedly. Only very low amounts of 3H-labeled ferrichrome were found in the cell. It is possible that the iron is mobilized in the membrane and that desferri-ferrichrome is released into the medium without having entered the cytoplasm. Growth on ferrichrome as the sole iron source was used to select revertants of T5 resistant ton A mutants. All revertants exhibited wild-type properties with the exception of partial revertants. In these 4 strains, as in the ton A mutants, the ton A protein was not detectable by SDS polyacrylamide gel electrophoreses of outer membranes. Albomycin resistant mutants were selected and shown to fall into 5 categories: 1) ton A; 2) ton B mutants; 3) mutants with no iron transport defects and normal ton A/ton B functions, which might be target site mutants; 4) mutants which were deficient in ferrichrome-mediated iron uptake but had normal ton A/ton B functions. We tentatively consider that the defect might be located in the active transport system of the cytoplasmic membrane; 5) a variety of mutants with the following general properties: most of them were resistant to colicin M, transported iron poorly, and, like ton B mutants, contained additional proteins in the outer membrane. The outer membrane protein patterns of wild-type and ton B mutant strains were compared by slab gel electrophoresis in an attempt to identify a ton B protein. It was observed that under most growth conditions, ton B mutants overproduced 3 proteins of molecular weights 74,000-83,000. In extracted, iron-deficient medium, both the wild-type and ton B mutant strains had similar large amounts of these proteins in their outer membranes. The appearance of these proteins was suppressed by excess iron in both wild-type and mutant. From this evidence it is apparent that the proteins appear as a response to low intracellular iron rather than being controlled by the ton B gene...

Biological Transport↗
PubMed1978

Iron uptake by Chang cells from transferrin, nitriloacetate and citrate complexes: the effects of iron-loading and chelation with desferrioxamine.

Iron uptake by Chang liver cells in culture is about thirty times as great when ferric nitriloacetate is used as a donor as when iron-transferrin is used. Iron uptake from ferric citrate is no greater than from iron-transferrin. Most of the intracellular iron derived from transferrin is found in the supernatant after 20 000 x g centrifugation of the cell homogenate for 40 min: about half of this is in the form of ferritin. Iron derived from ferric nitriloacetate is found largely in the membranous pellet after centrifugation and very little of this is in the form of ferritin. Iron incorporated in cytosol ferritin is easily available for chelation by desferrioxamine and this process is facilitated by ascorbic acid. Membrane-bound iron is less available for chelation. This tissue culture model forms a convenient basis for the study of iron overlead and iron chelation.

Cells, Cultured↗
PubMed1979

The mechanism of hepatic iron uptake from native and denatured transferrin and its subcellular metabolism in the liver cell.

Hepatic iron uptake and metabolism were studied by subcellular fractionation of rat liver homogenates after injection of rats with a purified preparation of either native or denatured rat transferrin labelled with 125I and 59Fe. (1) With native transferrin, hepatic 125I content was maximal 5 min after injection and then fell. Hepatic 59Fe content reached maximum by 16 h after injection and remained constant for 14 days. Neither label appeared in the mitochondrial or lysosomal fractions. 59Fe appeared first in the supernatant and, with time, was detectable as ferritin in fractions sedimented with increasingly lower g forces. (2) With denatured transferrin, hepatic content of both 125I and 59Fe reached maximum by 30 min. Both appeared initially in the lysosomal fraction. With time, they passed into the supernatant and 59Fe became incorporated into ferritin. The study suggests that hepatic iron uptake from native transferrin does not involve endocytosis. However, endocytosis of denatured transferrin does occur. After the uptake process, iron is gradually incorporated into ferritin molecules, which subsequently polymerize; there is no incorporation into other structures over 14 days.

Animals↗
PubMed1979

Novel iron uptake system specified by ColV plasmids: an important component in the virulence of invasive strains of Escherichia coli.

The enhanced virulence of invasive strains of Escherichia coli carrying ColV plasmids was shown to be due to a novel plasmid-mediated iron uptake system. Possession of a ColV plasmid conferred strong selective advantage on the host bacterial strain in experimental infections unless excess iron was administered in the inoculum. Moreover, supplementation of defined minimal medium with transferrin to complex available iron caused marked limitation of the growth of plasmid-free strains but had no effect on strains carrying a ColV plasmid. The activity of an efficient iron uptake process was clearly shown by experiments with a mutant of E. coli deficient in enterochelin biosynthesis. Although the mutant was dependent on the presence of citrate in the growth medium to facilitate iron transport, colicinogenic derivatives did not require added citrate for growth. Radioactive iron was shown to be taken up rapidly by nongrowing cells of the plasmid-carrying strain. Furthermore, it was observed that repression of the synthesis of specific outer membrane proteins normally induced by conditions of iron deficit was maintained after a shift of the colicinogenic strains from a rich medium to a medium low in iron. The ColV plasmid-mediated iron uptake system was independent of the active iron transport mechanisms known in E. coli, but like them it required tonB activity as a source of energy.

Animals↗
PubMed1978

Coordination chemistry of microbial iron transport compounds: rhodotorulic acid and iron uptake in Rhodotorula pilimanae.

The mechanism by which iron uptake is facilitated by the siderophore rhodotorulic acid (RA) in the yeast Rhodotorula pilimanae was investigated with radioactively labeled Fe and RA and kinetically inert, chromic-substituted RA complexes. The weight of the evidence supports a model in which RA mediates iron transport to the cell but does not actually transport iron into the cell. It is proposed that RA exchanges the ferric ion at the cell surface with a membrane-bound chelating agent that completes the active transport of iron into the cell. Uptake of 55Fe in ferric rhodotorulate was much more rapid than uptake of RA itself. Two exchange-inert chromic complexes of RA showed no uptake.

Biological Transport, Active↗
PubMed1976

Iron uptake in colicin B-resistant mutants of Escherichia coli K-12.

Four classes of colicin B-resistant mutants of Escherichia coli K-12 were examined for defects in iron uptake. All four mutant classes (cbt, exbC, exbB, and tonB) were defective in the uptake of ferri-ennterochelin. The tonB mutant was also defective in citrate-, ferrichrome-, and rhodoturulic acid-mediated iron uptake. The defects in iron transport were reflected in increased sensitivity to iron chelators and to chromium and aluminium salts, and in hypersecretion of enterochelin. One of the mutants (cbt) was apparently defective in outer membrane ferri-enterochelin receptor activity. aroE derivatives (unable to synthesize enterochelin) of the four mutant classes and the parent strain produced increased amounts of two outer membranes polypeptides when grown under iron stress. These polypeptides are implicated in ferri-enterochelin receptor activity.

2,2'-Dipyridyl↗
PubMed1977

Involvement of outer membrane proteins in enterochelin-mediated iron uptake in Escherichia coli.

Escherichia coli K-12 grown in iron-deficient media contained a large amount of outer membrane proteins O-2a, O-2b, and O-3, while cells grown in iron-supplemented media contained far smaller amounts of these proteins. The iron uptake by the iron-deficient cells was significantly stimulated in the presence of enterochelin, while that by the iron-rich cells was not. The outer membrane isolated from cells grown in the iron-deficient media showed enterochelin-stimulated binding of iron, while the outer membrane from iron-rich cells and cytoplasmic membranes from both types of cells did not show such binding activity. The amount of iron bound by the outer membrane was almost equivalent to the amount of O-2a, O2b, or O-3, irrespective of the amount of these proteins in the outer membrane, which is controlled by the amount of iron in the medium. Small particles rich in these proteins were prepared from cells by EDTA extraction. The particles were active in enterochelin-mediated iron binding and the amount of iron bound was equivalent to the amount of each of these proteins in the particles. Although the outer membrane of E. coli B was as active in iron binding as that of E. coli K-12, it did not possess an appreciable amount of O-2a. Gel electrophoretic analysis revealed that 9-2b and 9-3 were identical with the proteins missing mutants feuB and feuA, respectively.

Biological Transport, Active↗
PubMed1978

Defective iron uptake and globin synthesis by erythroid cells in the anemia of the Belgrade laboratory rat.

Erythroid cell iron uptake and globin synthesis were studied in the anemia of the Belgrade Laboratory rat (gene symbol, b), an autosomal recessive trait characterized by hypochromia and hyperferrinemia. Reticulocyte protein and globin synthesis, as measured in vitro by the incorporation of 3H-L-leucine, were significantly diminished in b/b animals, although no major imbalance between alpha-and beta-chain production was observed in b/b reticulocytes. The incorporation in vitro of 3H-L-methionine into marrow cell globin demonstrated no difference between b/b animals and +/? control animals in the proportion of alpha-to beta-chain production. The transfer of iron from plasma to reticulocytes, as measured in vitro by the uptake of 59Fe, was significantly decreased in b/b animals; Sephadex G 200 chromatography of b/b red cell lysates did not reveal the accumulation of 59Fe in nonhemoglobin fractions found when heme synthesis was inhibited with isoniazid. The magnitude of the reticulocyte iron-uptake defect was greater than the reticulocyte globin-synthesis defect, suggesting that the former is the primary lesion.

Anemia↗
PubMed1977

Iron uptake by immature erythroid cells. Mechanism of dependence on metabolic energy.

The mechanism by which the utilization of transferrin-bound iron is linked with cellular metabolism was investigated using rabbit reticulocytes and bone marrow cells. The rate of metabolism was altered by the use of inhibitors which act at different sites in the metabolic pathway (NaF, sodium fluoroacetate, rotenone, 2,4-dinitrophenol, NaCN) and by the addition of metabolic substrates (inosine, sodium pyruvate, sodium lactate). Measurements were made of the rates of iron and transferrin uptake and, in many of the experiments of cellular ATP and NADH concentrations. The results showed that there was a significant correlation between the rate of iron uptake and the ATP concentration of the cells, but no correlation was found with the NADH concentration. The rate of transferrin uptake was inhibited to a lesser degree than that of iron uptake, and only when the ATP concentration had fallen below that necessary to inhibit iron uptake. It is concluded that the rate of uptake of transferrin-bound iron by immature erythroid cells is dependent on the intracellular concentration of ATP but is independent of the NADH concentration.

Adenosine Triphosphate↗
PubMed1979

Normal iron absorption and decreased red cell iron uptake in the aged.

Absorption of iron was studied with a double-isotope technique that allowed differentiation between "mucosal uptake," "mucosal transfer," and ultimate "retention" of iron. A physiologic dose of ferrous sulfate was administered to 25 healthy young adults, 40 active aged persons, and 20 patients with uncomplicated iron deficiency. Radioactivity was measured with a whole-body scanner. Iron absorption values were not decreased in aged subjects compared to young adults. Mucosal uptake, mucosal transfer, and retention of iron were equally increased in both young and old patients with iron deficiency. In 12 young adults and 33 aged persons red cell iron uptake was studied in addition to iron absorption. Young adults utilized 91% of the retained, orally administered iron and the aged only 66%. An increase in ineffective erythropoiesis in old age is suggested.

Absorption↗
PubMed1979

The recovery of iron uptake in erythropoietic bone marrow following large field radiotherapy.

Large X-ray fields, such as those used to irradiate major lymph-node areas in the treatment of lymphomas, often irradiate large areas of haemopoietic bone marrow. The absorbed doses received by the marrow are close to the tolerance level. Quantitative scanning of the bone marrow, using 52Fe and a digital whole-body scanner, has been carried out in a series of 22 patients treated by radiotherapy up to nine years previously in order to assess the extent and recovery of their erythropoietic marrow. The results showed large variations from patient to patient; in some patients the iron uptake in the marrow returned to near normal levels in two to three years, while in others the uptake remained suppressed after seven to eight years. The tolerance dose for the bone marrow appeared to be about 1100 ret. There was some evidence of a more rapid recovery of erythropoietic function in males than females, but no evidence to show that age of patient, type of disease or whether chemotherapy had been used influenced the results. Patients who showed a decreased iron uptake in an irradiated region of marrow generally showed a compensating increased uptake in unirradiated regions, which in some cases was associated with anaemia.

Adolescent↗
PubMed1977

Effect of iron saturation of transferrin on hepatic iron uptake: an in vitro study.

Studies were performed to delineate the effect of percentage of saturation of transferrin and total iron concentration on the rate of uptake of iron by the perfused rat liver. Normal and iron-deficient rat livers were perfused with sera that contained varying concentrations of 59Fe-labeled iron and transferrin saturation. Varying the percentage of saturation of transferrin while maintaining a constant concentration of iron did not influence the hepatic uptake of iron. However, raising the concentration of iron in the perfusate while maintaining a constant saturation of transferrin did increase the uptake of iron by the liver. At similar concentrations of iron and transferrin saturation, iron-deficient livers took up greater amounts of iron than did normal livers. In our experiments, the hepatic uptake of transferrin-bound iron is determined by (1) the concentration of iron in perfusate and (2) the status of iron stores in the liver being perfused.

Animals↗