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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Food iron absorption data on 853 Indian women were compared to the haemoglobin concentrations, other iron-related measurements and the absorption of a reference dose of 3 mg iron given as ferrous ascorbate. The serum ferritin concentration was identified as the best predictor of the absorption of the reference dose (r = -0.54, p less than 0.0001). These two measurements were then compared in terms of their relative ability to predict the absorption of iron from 10 individual meals. Results were comparable, with correlations for the pooled data of -0.50 (p less than 0.0001) for the serum ferritin and 0.47 (p less than 0.0001) for the reference dose. Since serum ferritin is a simple and non-invasive test, it may represent the more satisfactory way of standardising food iron absorption results to a common iron status in field studies. However, the value of such an approach is limited by the wide confidence limits of the relationship between food iron absorption and both the other measurements.
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PMID:Relationship between absorption of inorganic and food iron in field studies. 359 14

Despite widespread use of supplements, few studies have been conducted to determine if supplement users have better nutritional status. Using data from the second National Health and Nutrition Examination Survey (NHANES II), mean values of five iron status indicators (hemoglobin, mean corpuscular volume, transferrin saturation, erythrocyte protoporphyrin, and serum ferritin) and dietary intakes of several nutrients and food groups were compared between regular supplement users and nonusers aged 1-19 y. Users consumed more vitamin C and fruits and vegetables than nonusers in several age-sex groups. No significant differences in mean Fe status indicator values were observed except for hemoglobin for the 3-4-y olds and serum ferritin for the 5-10-y olds. In both cases, users had higher values than nonusers. In general, Fe status was not associated with supplement use but the reason cannot be identified from this survey.
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PMID:Comparison of dietary intakes and iron status of vitamin-mineral supplement users and nonusers, aged 1-19 years. 366 81

Ascorbic acid retards ferritin degradation in K562 erythroleukemia cells leading to an increase in the availability of cellular iron (Bridges, K. R., and Hoffman, K. E. (1986) J. Biol. Chem. 261, 14273-14277). To explore the mechanism of this effect, the influence of ascorbate on subcellular ferritin distribution was examined. Cellular ferritin was pulse-labeled with 59Fe for 2 h, after which the cells were hypotonically lysed and fractionated on an 8% Percoll density gradient. Immediately after the labeling, all of the ferritin was in the cytoplasmic fractions at the top of the gradient. When the labeling was followed by a 24-h period of growth, a portion of the ferritin shifted to the lysosome-associated fractions at the bottom of the gradient, consistent with lysosomal autophagy of cytoplasmic ferritin. When ascorbate was added to the culture medium during the 24-h incubation, the magnitude of the shift was reduced. This process was also examined by size-fractionation of the contents of labeled cells using a Sepharose CL-6B column. Immediately after labeling, ferritin emerged from the column in two peaks, indicating the existence of both ferritin monomer and aggregates within the cytoplasm. After a 24-h period of growth, the monomer peak disappeared, while a new ferritin peak coincident with lysosomes emerged again, indicative of lysosomal autophagy of ferritin. In cells cultured with ascorbate for 24-h, there was a marked attenuation of the shift of ferritin to the lysosomal fractions. The monomer peak disappeared, as in the controls, but there was instead, an accumulation of ferritin as cytoplasmic aggregates. The total ferritin content of the ascorbate-treated cells was increased by 4-fold over that of the control. These experiments indicate that ascorbate blocks the degradation of cytoplasmic ferritin by reducing lysosomal autophagy of the protein. The access to the cell of the potentially toxic iron stored within the ferritin molecule is thereby increased.
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PMID:Ascorbic acid inhibits lysosomal autophagy of ferritin. 366 2

Conjugated-Schiff's-base-type fluorescence was measured in iron-depleted samples and chloroform extracts of human spleen haemosiderin. Incubation of ferritin with liposomes and ascorbate led to the formation of compounds with similar fluorescence properties. Analysis of protein subunits by SDS/polyacrylamide-gel electrophoresis confirmed that ferritin was damaged in incubations with ascorbate. Since previous studies have shown that intact ferritin is resistant to proteolytic degradation, it is suggested that haemosiderin may be a product of oxidative reactions involving ferritin and lipid.
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PMID:Haemosiderin-like properties of free-radical-modified ferritin. 382 50

To study the influence of acidosis on free radical formation and lipid peroxidation in brain tissues, homogenates fortified with ferrous ions and, in some experiments, with ascorbic acid were equilibrated with 5-15% O2 at pH values of 7.0, 6.5, 6.0, and 5.0, with subsequent measurements of thiobarbituric acid-reactive (TBAR) material, as well as of water- and lipid-soluble antioxidants (glutathione, ascorbate, and alpha-tocopherol) and phospholipid-bound fatty acids (FAs). Moderate to marked acidosis (pH 6.5-6.0) was found to grossly exaggerate the formation of TBAR material and the decrease in alpha-tocopherol content and to enhance degradation of phospholipid-bound, polyenoic FAs. These effects were reversed at pH 5.0, suggesting a pH optimum at pH 6.0-6.5. It is concluded that acidosis of a degree encountered in ischemic brain tissues has the potential of triggering increased free radical formation. This effect may involve increased formation of the protonated form of superoxide radicals, which is strongly prooxidant and lipid soluble, and/or the decompartmentalization of iron bound to cellular macromolecules like ferritin.
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PMID:Influence of acidosis on lipid peroxidation in brain tissues in vitro. 398 24

Ferritin-Fe(III) was rapidly and quantitatively reduced and liberated as Fe(II) by FMNH(2), FADH(2) and reduced riboflavin. Dithionite also released Fe(II) from ferritin but at less than 1% of the rate with FMNH(2). Cysteine, glutathione and ascorbate gave a similar slower rate and yielded less than 20% of the total iron from ferritin within a few hours. The reduction of ferritin-Fe(III) by the three riboflavin compounds gave complex second-order kinetics with overlapping fast and slow reactions. The fast reaction appeared to be non-specific and may be due to a reduction of Fe(III) of a lower degree of polymerization, equilibrated with ferritin iron. The amount of this Fe(3+) ion initially reduced was small, less than 0.3% of the total iron. Addition of FMN to the ferritin-dithionite system enhanced the reduction; this is due to the reduction of FMN by dithionite to form FMNH(2) which then reduces ferritin-Fe(III). A comparison of the thermodynamic parameters of FMNH(2)-ferritin and dithionite-ferritin complex formation showed that FMNH(2) required a lower activation energy and a negative entropy change, whereas dithionite required 50% more activation energy and showed a positive entropy change in ferritin reduction. The effectiveness of FMNH(2) in ferritin-Fe(III) reduction may be due to a specific binding of the riboflavin moiety to the protein portion of the ferritin molecule.
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PMID:The release of iron from horse spleen ferritin by reduced flavins. 446 57

The level of assimilation of dietary iron is believed to have an important influence on iron status. To examine the effect of enhancing the availability of dietary iron on iron balance, 17 adult volunteer subjects were given 2 g of ascorbic acid daily with meals for 16 weeks. Serum ferritin levels before and after the study averaged 46 and 43 micrograms/L, respectively, indicating a negligible effect on iron stores. When vitamin C supplementation was continued for an additional 20 months in five iron-replete and four iron-deficient subjects, serum ferritin determinations again failed to indicate any significant effect of the vitamin C on iron reserves. These findings were not explained by intestinal adaptation to the enhancing effect of the vitamin, because radioisotopic measurements of nonheme iron absorption showed no reduction in the enhancing effect of 1 g of ascorbic acid after four months of megadoses of vitamin C. It is concluded that altering the availability of nonheme dietary iron has little effect on iron status when the diet contains substantial amounts of meat.
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PMID:The effect of high ascorbic acid supplementation on body iron stores. 646 73

Depletion of body iron stores is a major factor limiting regular blood donations by menstruating females. To determine if regular iron supplementation would solve this problem, we conducted a double-blind study in which menstruating female donors were randomly placed into one of three groups: one taking 39 mg elemental iron, a second taking 39 mg of iron plus 75 mg vitamin C, and a third taking 100 mg vitamin C daily. The women were requested to donate every 8 weeks for at least 1 year. Blood samples were taken on each donation for measurements of hemoglobin, total iron binding capacity (TIBC), and ferritin. In the two groups taking iron supplements hemoglobin and ferritin increased from baseline values and the TIBC decreased. The vitamin C control group showed decreases from baseline for hemoglobin and ferritin and increases in TIBC. Differences between groups taking iron supplements and the group not taking supplements were highly significant. Drop-out from the study was due to various causes; however, iron intolerance was uncommon. Minimal daily iron supplementation was beneficial in maintaining body iron stores and hemoglobin levels in menstruating females on a schedule of blood donation as often as every 8 weeks.
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PMID:Iron supplementation for menstruating female blood donors. 650 75

Ferritin-containing fractions with different degrees of iron loading were prepared. All ferritin fractions stimulated the peroxidation of bovine brain phospholipid liposomes, as measured by the formation of thiobarbituric acid-reactive material. This stimulation was increased in the presence of ascorbate. Iron salts of equivalent concentration to those of the ferritin fractions were more stimulatory to lipid peroxidation at the higher iron concentrations. None of the fractions inhibited ascorbate-dependent peroxidation in the presence of added iron salts.
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PMID:Effect of ferritin-containing fractions with different iron loading on lipid peroxidation. 684 36

Fibronectin is a major constituent of the fibroblast extracellular matrix. Fibronectin binds to collagen, mediates fibroblast adhesion to collagen, and is synthesized and secreted into the medium of cultured fibroblasts. Affinity-purified antibodies to fibronectin and collagen were localized using the peroxidase-antiperoxidase method or with ferritin-coupled secondary antibodies. Using human fibroblasts cultured under routine conditions, fibronectin and procollagen I react in a nonperiodic manner with: 1) approximately 10 nm extracellular fibrils, 2) cell membrane, and 3) membrane-associated vesicles. All fibrils react with both antibodies, suggesting some form of codistribution of fibronectin and collagen in these fibrils. Treatment with ascorbate leads to the development of a larger diameter extracellular fibril, approximately 40 nm in diameter. These large diameter fibrils are clearly collagen fibrils as documented by the procollagen antibody reaction. Importantly, fibronectin is bound to or a constituent of these "native" or cellular made collagen fibrils. Fibronectin and procollagen antibodies localized with the peroxidase-antiperoxidase method have a 70 nm axial repeat of reaction product on ascorbate-treated fibroblasts. Localization of antibodies with ferritin-labeled secondary antibodies is less satisfactory, but supports the basic observations made with the unlabeled antibody enzyme method. This observation rules out any potential criticisms. Although it is more difficult to observe with immunoferritin, there is an indication that antibodies to fibronectin react with an axial periodicity on cellular produced collagen fibrils.
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PMID:Fibronectin presence in native collagen fibrils of human fibroblasts: immunoperoxidase and immunoferritin localization. 701 12


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