Absorption of iron in rats with experimental enteritis*

Inflammatory conditions of the gastrointestinal tract and iron-deficiency anemia are very common in humans. Acute intestinal inflammation was pathologically established in rats by intraluminal administration of acetic acid into the duodenum and the proximal jejunum. The study included two control groups of intact (untreated) rats and sham-operated (saline-treated) rats for each intestinal segment. A third group of rats received acetic acid. The acetic acid-induced inflammatory process was established histopathologically and biochemically. Two days after treatment, iron absorption was measured using ligated 10-cm loops of proximal jejunum or ligated duodenum in which ⁵⁹Fe was injected intraluminally (n=6 in each group). In another four control groups (intact and sham-operated for each intestinal segment) and two acetic acid-treated groups, serosal-luminal secretion of ⁵⁹Fe was measured after intravenous injection (n=5 in each group). ⁵⁹Fe transfer from the lumens of the duodenum and jejunum to the portal system was significantly lower in those rats in whom inflammation was induced by acetic acid. There was no apparent serosal-luminal secretion of intravenously injected ⁵⁹Fe in any of the studied groups. We conclude that acetic acid-induced intestinal inflammation significantly reduces iron absorption by the duodenum and the proximal jejunum.     

In vitro loading of apoferritin.

This study compared the effect of loading apoferritin either with ferrous ammonium sulfate in various buffers or with ceruloplasmin and chelated ferrous iron. It was shown that loading of apoferritin with ferrous ammonium sulfate was dependent on buffer and pH, and was directly related to the rate of iron autoxidation. The ceruloplasmin-dependent loading of apoferritin, however, was unaffected by these factors. Isoelectric focusing and amino acid analysis of the differently loaded ferritins showed that ferrous ammonium sulfate loading of apoferritin resulted in the depletion of the basic amino acids, lysine and histidine, probably as a result of protein oxidation. No significant differences in amino acid composition was noted for ceruloplasmin-loaded ferritin. Furthermore, ferritin loaded with ferrous ammonium sulfate released more iron than either native or ceruloplasmin-loaded ferritin when either paraquat or EDTA was used as an iron mobilizing agent. We suggest that the loading of apoferritin with ferrous ammonium sulfate occurred as a result of iron autoxidation and may result in oxidation of amino acids and loss of integrity of the protein, and that ceruloplasmin may act as a catalyst for the incorporation of iron into apoferritin in a manner more closely related to that occurring in vivo.     

Ferrous sulfate toxicity a review of autopsy findings

Ferrous sulfate is the leading cause of accidental pediatric poisonings. Despite the requirement for child-resistant packaging for any oral iron product with 250 mg or more per container, the incidence has continued to increase. Although the clinical presentation of iron toxicity has been well described, pathologic findings in human tissue and correlation with clinical data are scant. We reviewed autopsies from the Armed Forces Institute of Pathology of 11 children who died from ferrous sulfate toxicity. Clinical data, morphologic changes, and iron levels in tissue were evaluated. The children’s ages ranged from 11 to 36 mo. Prominent iron deposition in gastric and small intestinal mucosa was associated with necrosis, with some cases demonstrating prominent vascular iron deposition. The clinical courses were rapid and progressed from Stage I to Stage III. These observations were correlated with increased levels of iron in various tissues, as determined by analytical atomic absorption spectrophotometry. The morphologic and chemical analysis data provide information on the pathogenesis of ferrous sulfate poisoning; the vascular iron deposition may be related to subsequent hemorrhage. In the liver the periportal necrosis is probably a direct cytopathic effect of the highest levels of iron carried to these cells by the portal blood flow.     

Absorption of therapeutic preparations of iron measured with a whole body counter

The Oxford Whole Body Counter was used to measure absorption from various therapeutic preparations of iron in five groups of subjects. Succinic acid enhanced absorption of iron when added to a solution of ferrous fumarate, but not when given with tablets of ferrous fumarate or ferrous sulphate. Ferrous fumarate plus ascorbic acid was absorbed better than ferrous fumarate alone but no better than ferrous sulphate. The addition of ascorbic acid and succinic acid to tablets of ferrous sulphate did not enhance absorption significantly.     

The mechanism of ferrous iron binding by suspensions of Bifidobacterium bifidum var. pennsylvanicus

Bifidobacterium bifidum var. pennsylvanicus acquires ferrous iron at a reasonable rate when this bacterium — in the resting state — is incubated with ferrous iron in either a modified Hanks' solution, ot Norris medium in which the bacteria had previously grown. Ferrous iron binding was substantially lower in unused Norris medium containing human milk whey, because it contained iron binding inhibitors that were degraded during bacterial growth. The inhibitors were identified as human milk whey components and bovine casein digest. The affinity of bacteria for ferrous iron was dependent on the iron concentration of the media. In modified Hanks' solution, the affinity of cells for iron at low iron concentrations was some 250-fold greater than that at high iron concentrations. Ferrous iron binding did not take place it a carbon source was omitted from the media or if the cells had previously been heated at 80°C for 20 min. Surface binding of ferrous iron to the bacterial membrane was minimal. Trypsin and microbial proteinase treatment of bacteria did not inhibit iron uptake, making an iron-specific receptor on bifidobacterial cell membranes unlikely. Iron binding by bifidobacteria is an energy-requiring process dependent upon the operation of a heat-sensitive enzyme machinery, and it does not involve an extracellular iron carrier.     

Kinetics Absorption Characteristics of Ferrous Glycinate in SD Rats and Its Impact on the Relevant Transport Protein

Ferrous glycinate (Fe-Gly) maintains high bioavailability in animals, but its exact absorption mechanism is still unknown. Here, we studied on the absorption kinetics of ferrous glycinate and its impact on the relevant transport protein in Sprague-Dawley (SD) rats. A total of 72 SD rats (male, BW 100?±?6.25 g) were randomly allotted to three treatments. These treatments were perfused with 1 mL of normal saline, ferrous sulfate (FeSO₄), and ferrous glycinate (71.35 mg/L as iron) separately. Four rats were selected from each treatment for collection of blood from the tails at certain times (15, 30, 45, 60, 75, 90, 120, 240, and 360 min) after gavage. Moreover, other six rats selected from each treatment were slaughtered for sampling after gavage at 2, 4, and 6 h to evaluate the expression of intestinal transport protein. Pharmacokinetic parameters of iron were determined by one-compartmental analysis. Compared with FeSO₄, the peak plasma concentration of iron (C _max) is higher in the rats given gavage with Fe-Gly (P?<?0.05). Four hours after gavage with Fe-Gly, the expression of divalent metal transporter 1 (DMT1) in the duodenum is significantly decreased (P?<?0.05), but the expression of ferroportin 1 (Fpn1) is significantly increased (P?<?0.05). This study indicates that Fe-Gly as iron sources can be absorbed more and utilized faster than FeSO₄, and they had different effects on the expression of intestinal transport protein.     

Difficulties in Ferrous Iron Mordant Hematoxylin Staining and Some Hematoxylin Substitutes

A gradual deterioration of intensity of sequence ferrous sulfate hematoxylin staining was traced, after elimination of hematoxylin quality as a cause, to a deterioration of the metal salt, associated with caking of the crystals. Fresh samples were also partly caked and ineffective. Ferrous ammonium sulfate was found also subject to the same deterioration. Ferrous chloride freshly prepared as a 1 M solution from iron wire under anaerobic conditions at biweekly intervals proved to be satisfactory as a mordant source. Of several other mordant dyes tested: gallein, brazilin and chromoxane pure blue B were the best, but none was equal to good hematoxylin.     

Effect of deoxyribonucleic acid on the production of reduced oxygen by bleomycin and iron

The binding of bleomycin to DNA in the presence and absence of ferric iron was measured by fluorescence spectroscopy. In millimolar concentrations of tris(hydroxymethyl)aminomethane, pH 7.5, approximately 80% of the bleomycin binds to DNA. Ferric iron seems to have no significant effect on the binding of DNA to bleomycin. The induction of oxygen uptake by ferrous iron and bleomycin was monitored in the presence and absence of DNA. DNA has no effect on the rate of oxygen uptake. Therefore, the iron binding site and the DNA binding site appear to be independent of each other. Under conditions where 80% of the bleomycin is bound to DNA, the ferrous iron-bleomycin-induced reduction of oxygen follows Michaelis-Menten kinetics. Ferrous iron autoxidation produces ethylene from methional. The addition of bleomycin greatly increases ethylene production. DNA, under conditions where 80% of the bleomycin is bound to DNA, inhibits ethylene production. Since ethylene is a measure of hydroxyl radical production, we conclude that DNA is able to compete with methional for the hydroxyl radical. We postulate a mechanism for DNA double-strand breaks in which the bleomycin selectively binds to DNA and recurrently produces the hydroxyl radical at that site. The localized generation of many hydroxyl radicals as provided by the proposed oxidation-reduction cycle mechanism may cause multiple strand breaks taking place on both strands of the DNA duplex leading to double-strand breaks. Since catalase, but not superoxide dismutase, is able to inhibit ferrous iron-bleomycin-induced products of the hydroxyl radical, hydrogen peroxide, but not the superoxide radical, is the immediate precursor of the hydroxyl radical.     

The effect of transferrin saturation on internal iron exchange

Radioiron was introduced into the intestinal lumen to evaluate absorption, injected as nonviable red cells to evaluate reticuloendothelial (RE) processing of iron, and injected as hemoglobin to evaluate hepatocyte iron processing. Redistribution of iron through the plasma was evaluated in control animals and animals whose transferrin was saturated by iron infusion. Radioiron introduced into the lumen of the gut as ferrous sulfate and as transferrin-bound iron was absorbed about half as well in iron-infused animals, and absorbed iron was localized in the liver. The similar absorption of transferrin-bound iron suggested that absorption of ferrous iron occurred via the mucosal cell and did not enter by diffusion. The decrease in absorption was associated with an increase in mucosal iron and ferritin content produced by the iron infusion. An inverse relationship (r = -0.895) was shown between mucosal ferritin iron and absorption. When iron was injected as nonviable red cells, it was deposited predominantly in reticuloendothelial cells of the spleen. Return of this radioiron to the plasma was only 6% of that in control animals. While there was some movement of iron from spleen to liver, this could be accounted for by intravascular hemolysis. Injected hemoglobin tagged with radioiron was for the most part taken up and held by the liver. Some 13% initially localized in the marrow in iron-infused animals was shown to be storage iron unavailable for hemoglobin synthesis. These studies demonstrate the hepatic trapping of absorbed iron and the inability of either RE cell or hepatocyte to release iron in the transferrin-saturated animal.     

Non-heme Iron as Ferrous Sulfate Does Not Interact with Heme Iron Absorption in Humans

The absorption of heme iron has been described as distinctly different from that of non-heme iron. Moreover, whether heme and non-heme iron compete for absorption has not been well established. Our objective was to investigate the potential competition between heme and non-heme iron as ferrous sulfate for absorption, when both iron forms are ingested on an empty stomach. Twenty-six healthy nonpregnant women were selected to participate in two iron absorption studies using iron radioactive tracers. We obtained the dose?Cresponse curve for absorption of 0.5, 10, 20, and 50?mg heme iron doses, as concentrated red blood cells. Then, we evaluated the absorption of the same doses, but additionally we added non-heme iron, as ferrous sulfate, at constant heme/non-heme iron molar ratio (1:1). Finally, we compare the two curves by a two-way ANOVA. Iron sources were administered on an empty stomach. One factor analysis showed that heme iron absorption was diminished just by increasing total heme iron (P?<?0.0001). The addition of non-heme iron as ferrous sulfate did not have any effect on heme iron absorption (P?=?NS). We reported evidence that heme and non-heme iron as ferrous sulfate does not compete for absorption. The mechanism behind the absorption of these iron sources is not clear.     

泥炭沼泽湿地关键元素地球化学特征及其对碳排放的影响机制

硫、铁是泥炭沼泽湿地（泥炭地）中重要的生源要素,其参与下的生物地球化学过程对泥炭地碳循环意义重大。选取德国中部两处典型的雨养型泥炭地高海拔样点（TBP）和低海拔样点（TSP）,通过原位采集泥炭剖面孔隙水和可溶性气体等,研究了硫、铁元素等地球化学变化规律,结合DOC、甲烷（CH₄）和二氧化碳（CO₂）浓度分布,探讨其对泥炭地碳排放的影响。研究结果表明：（1） TBP中总还原无机硫（TRIS）浓度随深度先增后减,且上部0-87 cm平均浓度远高于87 cm深度以下,上部硫酸盐还原作用强烈。结合上部亚铁、硫化氢（H₂S）浓度分布,得知该范围内H₂S主要是通过微生物硫酸盐还原作用（BSR）生成,同时H₂S在孔隙水扩散过程中易与亚铁结合为硫化亚铁,进而生成稳定的黄铁矿,这一反应过程在约60 cm处减缓。（2） TBP、TSP两处采样点中DOC与亚铁、硫酸盐均有较强相关性,是由于地下水位的波动影响氧化还原程度以及微生物活性。两处采样点DOC均与亚铁呈显著正相关关系,表明铁氧化物在厌氧环境中被还原溶解产生亚铁,与其结合的有机碳被释放到溶液中从而导致DOC浓度的升高。TBP中DOC与硫酸盐呈显著负相关关系,表明硫酸盐作为电子受体被还原的过程中消耗酸度使pH值升高,增强了其中微生物的活性,DOC浓度由此增加。（3） CH₄与硫酸盐、TRIS浓度在剖面上均呈现相反变化趋势,表明硫酸盐输入的增加以及硫酸盐还原活动均会抑制CH₄生成。CO₂/CH₄均大于4,表明硫酸盐作为替代电子受体会使厌氧条件下碳矿化转向多CO₂和少CH₄生成。此外,亚铁对于CH₄生成一定程度上会起到低促高抑的效果,而对于CO₂的生成的影响较弱。表明硫酸盐对于CH₄和CO₂生成的影响高于亚铁。研究着重探究硫、铁等关键元素地下部生物地球化学过程对碳排放的影响机制,研究结果可为泥炭地碳排放核算提供理论支撑。     

Metal ion substrate inhibition of ferrochelatase

Ferrochelatase catalyzes the insertion of ferrous iron into protoporphyrin IX to form heme. Robust kinetic analyses of the reaction mechanism are complicated by the instability of ferrous iron in aqueous solution, particularly at alkaline pH values. At pH 7.00 the half-life for spontaneous oxidation of ferrous ion is approximately 2 min in the absence of metal complexing additives, which is sufficient for direct comparisons of alternative metal ion substrates with iron. These analyses reveal that purified recombinant ferrochelatase from both murine and yeast sources inserts not only ferrous iron but also divalent cobalt, zinc, nickel, and copper into protoporphyrin IX to form the corresponding metalloporphyrins but with considerable mechanistic variability. Ferrous iron is the preferred metal ion substrate in terms of apparent k(cat) and is also the only metal ion substrate not subject to severe substrate inhibition. Substrate inhibition occurs in the order Cu(2+) > Zn(2+) > Co(2+) > Ni(2+) and can be alleviated by the addition of metal complexing agents such as beta-mercaptoethanol or imidazole to the reaction buffer. These data indicate the presence of two catalytically significant metal ion binding sites that may coordinately regulate a selective processivity for the various potential metal ion substrates.     

Ferrous iron is found in mesenteric lymph bound to TIMP-2 following hemorrhage/resuscitation

Extracellular iron has been implicated in the pathogenesis of post-injury organ failure. However, the source(s) and biochemical species of this iron have not been identified. Based upon evidence that distant organ injury results from an increase in intestinal permeability, we looked for ferrous iron in mesenteric lymph in anesthetized rats undergoing hemorrhage and fluid resuscitation (H/R). Ferrous iron increased in lymph from 4.7 nmol/mg of protein prior to hemorrhage to 86.6 nmol/mg during resuscitation. Utilizing immuno-spin trapping in protein fractions that were rich in iron, we tentatively indentified protein carrier(s) of ferrous iron by MALDI-TOF MS. One of the identified proteins was the metalloproteinase (MMP) inhibitor, TIMP-2. Antibody to TIMP-2 immunoprecipitated 74% of the ferrozine detectable iron in its protein fraction. TIMP-2 binds iron in vitro at pH 6.3, which is typical of conditions in the mesentery during hemorrhage, but it retains the ability to inhibit the metalloproteases MMP-2 and MMP-9. In summary, there is a large increase in extracellular ferrous iron in the gut in H/R demonstrating dysregulation of iron homeostasis. We have identified, for the first time, the binding of extracellular iron to TIMP-2.     

Iron uptake by the microaerophilic anaerobe Bifidobacterium bifidum var. pennsylvanicus

A system was designed to investigate ferrous iron transport into Bifidobacterium bifidum var. pennsylvanicus. It involved the incubation of the organisms with labeled ferrous iron in the Norris medium at pH 5, in which the bacteria had grown. Iron uptakes were similar under aerobic and anaerobic conditions. Ferrous but not ferric iron was taken up by the organisms. Iron uptake showed saturation kinetics and a marked temperature dependence. 2,4-Dinitrophenol and thenoltrifluoroacetate but not azide or trypsin treatment inhibited iron uptake. Zinc inhibited iron uptake competitively. Iron uptake from used medium was much greater than that from fresh medium at the same pH. It is concluded that ferrous iron uptake by the microorganisms is a carrier-mediated active phenomenon, inhibited by zinc, which may involve a substance elaborated into the medium by the organism.     

Lactic acid is absorbed from the small intestine of sheep

A series of experiments was conducted in vivo on anaesthetized sheep to explore the hypothesis that lactic acid is absorbed from the small intestine of sheep. Test solutions varying in lactic acid concentration, pH, osmolarity, and with fixed physiological concentrations of volatile fatty acids (VFAs), K+, Na+, NH4 +, Cl-, and PO4 (-3), were separately introduced into clean, surgically sealed pouches. Studies were undertaken in 27 sheep, each with three pouches in the middle of the duodenum, jejunum, and ileum. Samples were taken at 15-minute intervals for 60 minutes to determine the absorption rates. The experimental results showed that L- and D-lactic acid were absorbed from the pouches of the duodenum, jejunum, and ileum throughout the 60 minutes. In the test solutions with pH 5.3, 420mOsmol/kg, and 12.5mM lactic acid that are in vivo conditions of light lactic acidosis, the mean absorption rates of D-lactic acid and L-lactic acid pooled from three pouches were similar, 0.07micro mol/cm2/min and 0.06micro mol/cm2/min, respectively, based on absorptive surface area. The mean absorption rates of DL-lactic acid from the duodenum, jejunum, and ileum pouches were almost the same, 0.14, 0.14, and 0.11micro mol/cm2/min, respectively. The absorption of lactic acid varied depending on lactic acid concentration, and there was a curvilinear relationship between lactic acid concentration and its absorption rate. A decrease in pH and osmotic pressure resulted in significant, corresponding increases in the absorption of lactic acid (P<0.0001 and P<0.05, respectively).     

Ammonia Formation By The Reduction Of Nitrite/Nitrate By Fes: Ammonia Formation Under Acidic Conditions

One issue for the origin of life under a non-reducing atmosphere is the availability of the reduced nitrogen necessary for amino acids, nucleic acids, etc. One possible source of this nitrogen is the formation of ammonia from the reduction of nitrates and nitrites produced by the shock heating of the atmosphere and subsequent chemistry. Ferrous ions will reduce these species to ammonium, but not under acidic conditions. We wish to report results on the reduction of nitrite and nitrate by another source of iron (II), ferrous sulfide, FeS. FeS reduces nitrite to ammonia at lower pHs than the corresponding reduction by aqueous Fe^{+ 2}. The reduction follows a first order decay, in nitrite concentration, with a half-life of about 150 min (room temperature, CO₂, pH 6.25). The highest product yield of ammonia measured was 53%. Under CO₂, the product yield decreases from pH 5.0 to pH 6.9. The increasing concentration of bicarbonate, at higher pH, interferes with the reaction. Comparing experiments under N₂ CO₂ shows the interference of bicarbonate. The reaction proceeds well in the presence of such species as chloride, sulfate, and phosphate, though the yield drops significantly with phosphate. FeS also reduces nitrate and, unlike with Fe^{+ 2}, the reduction shows more reproducibility. Again, the product yield decreases with increasing pH, from 7% at pH 4.7 to 0% at pH 6.9. It appears that nitrate is much more sensitive to the presence of added species, perhaps not competing as well for binding sites on the FeS surface. This may be the cause of the lack of reproducibility of nitrate reduction by Fe^{+ 2} (which also can be sensitive to binding by certain species)     

Effect of Helicobacter pylori Infection on Iron Absorption in Asymptomatic Adults Consuming Wheat Flour Fortified with Iron and Zinc

Helicobacter pylori infection could impair iron absorption from fortified products. The objective of the study was to determine the effect of H. pylori infection on iron absorption from asymptomatic adults consuming wheat flour fortified with iron and zinc. The (13)C urea breath test was used to assess H. pylori infection. Twenty-four H. pylori-positive and 26 H. pylori-negative volunteers completed the study. On day?1, the subjects were randomized to receive for breakfast bread fortified with either ferrous sulfate and zinc sulfate or ferrous fumarate and zinc oxide. Bread fortified with ferrous sulfate was labeled with (59)Fe as sulfate, and bread fortified with ferrous fumarate was labeled with (55)Fe as fumarate. On day?3, they received the other type of bread, with the respective tracers. On days?18-23, a proton pump inhibitor was administered to all subjects. On day?24, all subjects received bread fortified with ferrous fumarate and zinc oxide labeled with (55)Fe as fumarate. H. pylori prevalence was 77.6%. The geometric mean (±1?SD) of iron absorption was significantly higher for ferrous sulfate than fumarate (6.9?±?2.9% vs. 0.5?±?3.5%, p?相似文献   

New method to study oxidative damage and antioxidants in the human small bowel: effects of iron application

Iron may induce oxidative damage to the intestinal mucosa by its catalyzing role in the formation of highly reactive hydroxyl radicals. This study aimed to determine iron-induced oxidative damage provoked by a single clinical dosage of ferrous sulfate and to elucidate the antioxidant defense mechanisms in the human small intestine in vivo. A double-lumen perfusion tube was positioned orogastrically into a 40-cm segment of the proximal small intestine in six healthy volunteers (25 +/- 5 yr). The segment was perfused with saline and subsequently with saline containing 80 mg iron as ferrous sulfate at a rate of 10 ml/min. Intestinal fluid samples were collected at 15-min intervals. Thiobarbituric acid reactive substances concentrations as an indicator of lipid peroxidation increased significantly from 0.07 microM (range, 0-0.33 microM) during saline perfusion to 3.35 microM (range, 1.19-7.27 microM) during iron perfusion (P < 0.05). Nonprotein antioxidant capacity increased significantly from 474 microM (range, 162-748 microM) to 1,314 microM (range, 674-1,542 microM) (P < 0.05). These data show that a single dosage of ferrous sulfate induces oxidative damage and the subsequent release of an antioxidant in the small intestine in vivo in healthy volunteers.     

Nutritional and technological behavior of stabilized iron-gluconate in wheat flour

Food fortification has been shown to be an effective strategy to overcome iron malnutrition. When a new iron compound is developed for this purpose, it must be evaluated from a nutritional and technological point of view before adding it into foods. In this way, we have evaluated ferrous gluconate stabilized by glycine as a new iron source to be used in wheat flour fortification. We performed biological studies in rats as well as sensory perceptions by human subjects in wheat flour fortified with this iron source. The productions of pentane as a rancidity indicator as well as the change of the sensorial properties of the biscuits made with stabilized ferrous gluconate-fortified wheat flour were negligible. Iron absorption in water from this iron source was similar to the reference standard ferrous sulfate. Nevertheless, because of the phytic acid content, iron absorption from fortified wheat flour decrease 40% for both iron sources. The addition of zinc from different sources did not modify iron absorption from ferrous sulfate and stabilized ferrous gluconate in water and wheat flour. The iron absorption mechanism as well as the biodistribution studies demonstrate that the biological behavior of this iron source does not differ significantly from the reference standard. These results demonstrate that the iron source under study has adequate properties to be used in wheat flour fortification. Nevertheless, more research is needed before considering this iron source for its massive use in food fortification.