Absorption of iron

Siderophore mediated absorption of iron. R. C. Hider, Struct. Bonding (Berlin), 1984, 58, 25 (324). 

Henry M, Jolivet JP, Livage J (1991) Aqueous Chemistry of Metal Cations Hydrolysis, Condensation and Complexation. 77 153-206 Hider RC (1984) Siderophores Mediated Absorption of Iron. 57 25-88 Hill HAO, Rdder A, Williams RJP (1970) The Chemical Nature and Reactivity of Cytochrome P-450. 8 123-151... 

Although iron deficiency is a common problem, about 10% of the population are genetically at risk of iron overload (hemochromatosis), and elemental iron can lead to nonen2ymic generation of free radicals. Absorption of iron is stricdy regulated. Inorganic iron is accumulated in intestinal mucosal cells bound to an intracellular protein, ferritin. Once the ferritin in the cell is saturated with iron, no more can enter. Iron can only leave the mucosal cell if there is transferrin in plasma to bind to. Once transferrin is saturated with iron, any that has accumulated in the mucosal cells will be lost when the cells are shed. As a result of this mucosal barrier, only about 10% of dietary iron is normally absorbed and only 1-5% from many plant foods. 

C Ascorbic acid Coenzyme in hydroxylation of proline and lysine in collagen synthesis antioxidant enhances absorption of iron Scurvy—impaired wound healing, loss of dental cement, subcutaneous hemorrhage... 

At intakes above approximately 100 mg/d, the body s capacity to metabofize vitamin C is samrated, and any further intake is excreted in the urine. However, in addition to its other roles, vitamin C enhances the absorption of iron, and this depends on the presence of the vitamin in the gut. Therefore, increased intakes may be beneficial. Evidence is unconvincing that high doses of... 

Absorption of Iron From the Small Intestine Is Tightly Regulated... 

Enterocytes in the proximal duodenum are responsible for absorption of iron. Incoming iron in the Fe " state is reduced to Fe " by a ferrireductase present on the surface of enterocytes. Vitamin C in food also favors reduction of ferric iron to ferrous iron. The transfer of iron from the apical surfaces of enterocytes into their interiors is performed by a proton-coupled divalent metal transporter (DMTl). This protein is not specific for iron, as it can transport a wide variety of divalent cations. 

Figure 50-4. Absorption of iron. is converted to Fe + by ferric reductase, and Fe " is transported into the enterocyte by the apicai membrane iron transporter DMTl. Fieme is transported into the enterocyte by a separate heme transporter (HT), and heme oxidase (FiO) reieases Fe from the heme. Some of the intraceiiuiar Fe + is converted to Fe + and bound by ferritin. The remainder binds to the basoiaterai Fe + transporter (FP) and is transported into the biood-stream, aided by hephaestin (FiP). in piasma, Fe + is bound to the iron transport protein transferrin (TF). (Reproduced, with permission, from Ganong WF Review of Medical Physiology, 21 st ed. McGraw-Hill, 2003.)...

Transferrin binds iron, transporting it to sites where it is required. Ferritin provides an intracellular store of iron. Iron deficiency anemia is a very prevalent disorder. Hereditary hemochromatosis has been shown to be due to mutations in HFE, a gene encoding the protein HFE, which appeats to play an important role in absorption of iron. 

New information has been added in appropriate chapters on hpid rafts and caveolae, aquaporins, connexins, disorders due to mutations in genes encoding proteins involved in intracellular membrane transport, absorption of iron, and conformational diseases and pharmacogenomics. 

Camire (2002) showed that texturization does not seem to have a great effect on mineral retention and bioavailability. Others have reported increased retention of ascorbic acid in rice- and maize-based snacks (Hazell and Johnson, 1989 Plunkett and Ainsworth, 2007), increased iron diffusibility and absorption of iron-complexed protein (Poltronieri et al, 2000 Watzke, 1998), and no difference in iron and zinc absorption in human subjects fed textured bran-flour (Fairweather-Tait et al, 1989). 

Since there is no true excretion of iron from the body, iron-deficiency anemia occurs mostly because of inadequate absorption of iron or excess blood loss. Inadequate absorption may occur in patients who have congenital or acquired intestinal diseases, such as inflammatory bowel disease, celiac disease, or bowel resection. Achlorhydria and diets poor in iron also may contribute to poor absorption of iron. In contrast, iron deficiency also may occur in patients who exhibit a higher rate of iron loss from the body. This is manifested in... 

Hemoxl Haem oxygenase Catabolism of cellular haem to bilirubin, carbon monoxide and free iron hemoxl- - mice (Poss and Tonegawa, 1997) Impaired haem catabolism impaired absorption of iron from meat anaemia inflammation... 

Primary haemochromatosis, caused by inappropriately high absorption of iron... 

Main pathophysiological mechanisms of iron loading that may result in an infectious risk 1.1 Increased gastrointestinal absorption of iron I.2a Parenteral administration of iron I.2b Increased release of iron in the blood stream (haemolysis) 1.3 Increased inhalation of iron II Chronic inflammation III Diabetic ketoacidosis increased... 

Decrease absorption of iron, telracydine, quinolones, bisphosphonates, phenyloin, and fluoride when given concomitantiy... 

No effect on apparent absorption of iron, manganese or copper although not statistically significant, absorption of zinc tended to decrease with increased phytic acid intake (44)... 

Gillooly et al. (42J observed that iron absorptions were markedly decreased by the additon of sodium phytate to test meals while similarly marked decreases in zinc absorption have been observed (36,43 Table II). Contradictory results were recently reported (23.44). Addition of high levels (1.5 to 2.9g/day) of sodium phytate did not significantly affect the apparent absorption of iron, manganese, copper or zinc. 

For the second level, the correction of modest iron deficiency, various iron salts have been recommended or prescribed as iron supplements. These salts have included iron(II) succinate, fumarate, gluconate, and lactate, and iron(III) citrate - or, better (335), ammonium iron(III) citrate as iron(III) citrate seems to be a poorly characterized compound (337). There are two main problems. The first is the ease of oxidation of the iron(II) salts, particularly the lactate. The second is that absorption of iron from these sources is very inefficient (57), as species such as Fe (aq), Fe (aq), and simple hydrolysed entities such as FeOH (aq) cross membranes such as those that constitute the wall of... 

Gut absorption changes Greater absorption of iron and calcium (or toxic... 

Gastric acid and ascorbic acid facilitate the absorption of iron. Therefore, bioavailability of iron ingested with food is considerably decreased and also enteric-coated iron preparations are absorbed to a lesser extend. Fixed combinations with ascorbic acid increase the absorption of iron by at least 30%. However such increased uptake seems to have little advantage over a modest increase of dose. 

In iron-deficient rats, nickel enhanced the absorption of iron (Nielsen 1980 Nielsen et al. 1980, 1984). This effect of nickel was only observed when ferric sulfate was given. No interaction was observed when iron was given as a 60% ferric/40% ferrous sulfate mixture. It has been proposed that nickel facilitates the passive diffusion of ferric ions by stabilizing the transport ligand (Nielsen 1980). 

Antacids may decrease the gastrointestinal absorption of iron. Iron may chelate or decrease the gastroin-... 

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