Liver, iron storage

Dosing for iron should be divided equally into two to three doses daily. An empty stomach (1 hour before or 2 hours after a meal) is preferred for maximal absorption. After absorption, iron binds to transferrin in the plasma and is transported to the muscles (for myoglobin), liver (for storage), or bone marrow (for red cell production). Iron is not actively excreted from the body but is lost through other measures already described.7 Some studies suggest that iron absorption may be... 

Ferrihydrite is the iron oxide with the most widespread distribution in living organisms. In the form of ferritin, an iron storage protein, it is found in all organisms from bacteria through to man (in heart, spleen and liver). It occurs in plants as phytoferritin (review by Seckback, 1982). Ferritin plays a key role in iron metabolism it maintains... 

Iron is best absorbed in the ferrous form or as heme. It is believed that transferrin, transported into the small intestine from the liver via bile, carries iron into the intestinal mucosal cells. Though about 16 mg of iron enter these cells every day, only 1-2 mg finds its way into the bloodstream. The rest remains bound to an iron storage protein called ferritin and is eventually lost in the feces in the normal sloughing-off process. Iron absorption also depends on its bioavail-... 

Bacon BR, Britton RS Hemochromatosis and other iron storage disorders, in Schiff ER, Sorrell MF, MaddreyWC,et al. (eds) Schiff s Diseases of the Liver. Philadelphia, Lippincott Williams and Wilkins, 2003, pp. 1187-1205. 

RNA secondary structure plays a role in the regulation of iron metabolism in eukaryotes. Iron is an essential nutrient, required for the synthesis of hemoglobin, cytochromes, and many other proteins. However, excess iron can be quite harmful because, untamed by a suitable protein environment, iron can initiate a range of free-radical reactions that damage proteins, lipids, and nucleic acids. Animals have evolved sophisticated systems for the accumulation of iron in times of scarcity and for the safe storage of excess iron for later use. Key proteins include transferrin, a transport protein that carries iron in the serum, transferrin receptor, a membrane protein that binds iron-loaded transferrin and initiates its entry into cells, and ferritin, an impressively efficient iron-storage protein found primarily in the liver and kidneys. Twenty-four ferritin polypeptides form a nearly spherical shell that encloses as many as 2400 iron atoms, a ratio of one iron atom per amino acid (Figure 31.37). 

Haemosiderosis (HS) denotes iron storage in the organism, whereby iron deposition in the liver is < 0.5 g/100 g liver WW. Iron deposition occurs almost exclusively in the RES parenchymal cells are rarely affected. Haemosiderosis exists in two forms (7.) absolute HS resulting in generalized iron deposition in the body as a whole, or (2.) relative HS localized in a certain organ with the rest of the body showing normal iron distribution. Haemosiderosis does not cause haemochromatosis. (s. tab. 31.17)... 

Aceruloplasminaemia is a very rare, autosomal recessive disease with diffuse iron overload. It is caused by a mutation of the ceruloplasmin gene. This leads to excessive iron storage, mainly in the brain, liver and pancreas. The principal symptoms are increased serum ferritin, decreased serum iron and transferrin saturation as well as extrapyramidal disturbances, retinal degeneration, cerebellar ataxia and diabetes mellitus. (486-488) (s. tab. 31.17)... 

After being transported in increased quantities to the liver, iron is mostly stored as haemosiderin and ferritin in the hepatocytes of the lobular periphery. Initially, this liver cell siderosis does not impair the function of hepatocytes, as iron is absorbed by lysosomes. Iron storage commences in lobular zone 1 and progresses to zone 3. Gradually, the cells of the whole lobule become involved in iron deposition, mainly in the form of centroaxial pigment pathways, with enhanced iron deposition in the periportal area (haemosiderin granules). (422, 442)... 

Iron removal In the case of increased iron storage in the liver or in hypersiderinaemia, iron removal has been reported to give better therapeutic results. (217, 243)... 

Ceruloplasmin seems not absolutely necessary for life, as several people have been found to lack this protein. However, these people suffer froni diabetes and retinal degeneration, and iron deposits occur in their brain, liver, and pancreas (I larris, 1995). The exact physiological role of ceruloplasmin remains unclear, but it is related somehow to the transfer of iron in and out of ferritin. Ferritin is a huge multisubunit iron storage protein with an overall molecular weight of 450 kDa. It can hold up to 2500 iron atoms. Studies have shown that iron can spontaneously be inasrporated into ferritin, and also that ceruloplasmin can load iron into ferritin. 

A dominantly inherited form of iron storage disease results from mutations in ferroportin (SLCllAS). Here iron storage occurs primarily in macrophages, not in liver parenchyma. Iron accumulation appears to be more common in Africans than Europeans, and although diet may play a major role, it is thought that there is also a genetic predisposition that may account for the increased iron burden. ... 

Measurement of serum ferritin levels has diagnostic utility. In iron deficiency anemia (discussed later), serum ferritin levels are low in iron storage disease, the levels are high. However, serum ferritin levels can also be elevated under many other circumstances, including liver diseases and chronic inflammatory diseases. 

While not the most toxic, plutonium is the most likely transuranium element to be encountered. Plutonium commonly exists in aqueous solution in each of the oxidation states from III to VI. However, under biological conditions, redox potentials, complexa-tion, and hydrolysis strongly favor Pu(IV) as the dominant species (27, 28). It is remarkable that there are many similarities between Pu(IV) and Fe(III) (Table I). These include the similar charge per ionic-radius ratios for Fe(III) and Pu(IV) (4.6 and 4.2 e/k respectively), the formation of highly insoluble hydroxides, and similar transport properties in mammals. The majority of soluble Pu(IV) present in body fluids is rapidly bound by the iron transport protein transferrin at the site which normally binds Fe(III). In liver cells, deposited plutonium is initially bound to the iron storage protein ferritin and... 

Iron losses are about 1 mg daily through various excretions. It is noted that iron storage occurs in the form of ferritin and hemosiderin in the reticulo-enoth-lelian cells of the liver, spleen, and bone marrow, and in the parenchymal cells of the liver. 

Ferritin, Epadora Ferrofolin Ferrol Ferrosprint Sanifer Sideros Uniter. Major iron storage protein found in spleen, liver and intestinal mucosa of vertebrates widely distributed in the plant and animal kingdoms. I soln and... 

The evidence that ceruloplasmin (Cp) (E.C. 1.12.3,1) is a direct molecular link between copper and iron metabolism is summarized. Copper deficiency results in low plasma Cp and iron, reduced iron mobilization, and eventually anemia, even with high iron storage in the liver. Cp controls the rate of iron uptake by transferrin. Transferrin plays a key role in the availability of iron for the biosynthesis of hemo-globin in the reticulocytes. The ferroxidase activity of Cp results in the reduction of free iron ion generating a conr centration gradient from the iron stores to the capillary system, thus promoting a rapid iron efflux in the reticuloendothelial system. It has been confirmed both in vivo and in the perfused liver that lOr M Cp specifically induces a rapid rise in plasma iron. 

Hemosiderin, a mammalian non-heme iron storage protein with a similar function to ferritin. It contains iron oxyhy-droxide cores similar to those of ferritin, and it has been reported that these cores are present as large, dense, membrane-bound aggregates in vivo. It is assumed that hemosiderin is produced by lysosomal degradation of ferritin or possibly of ferritin polymers. Hemosiderin is deposited in the liver and spleen, especially in diseases such as pernicious anemia or hemochromatosis. The deposits are yellow to brown-red pigments. The iron content of hemosiderin is about 37%. Nonheme iron is also abundantly present in the brain in different forms. In the so-called high-molecular-weight complexes, iron is bound to hemosiderin and ferritin. The total amount of iron may differ in health and disease [F. A. Fischbach et al, J. Ultrastruct. Res. 1971, 37, 495 M. P. Weir, T. J. Peters, Biochem.J. 1984, 223, 31]. 

The principal iron-storage compounds of vertebrates are the proteins ferritin, found mainly in liver, and haemosiderin, found in spleen and muscles. 

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