Transferrin receptors iron absorption/transport

Transferrin receptor-2 Iron transport into hepatocytes Hereditary haemochromatosis (Camaschella et ah, 2000) increased iron absorption parenchymal iron overload... 

Absorption, transport, and storage of iron. Intestinal epithelial cells actively absorb inorganic iron and heme iron (H). Ferrous iron that is absorbed or released from absorbed heme iron in the intestine (1) is actively transported into the blood or complexed with apoferritin (AF) and stored as ferritin (F). In the blood, iron is transported by transferrin (Tf) to erythroid precursors in the bone marrow for synthesis of hemoglobin (Hgb) (2) or to hepatocytes for storage as ferritin (3). The transferrin-iron complexes bind to transferrin receptors (TfR) in erythroid precursors and hepatocytes and are internalized. After release of the iron, the TfR-Tf complex is recycled to the plasma membrane and Tf is released. Macrophages that phagocytize senescent erythrocytes (RBC) reclaim the iron from the RBC hemoglobin and either export it or store it as ferritin (4). Hepatocytes use several mechanisms to... 

Figure 13-1 Free representation of some of the elements known to play a role in iron absorption, iron distribution and iron accumulation. The central circle indicates that in ways that are still not fully imderstood these various elements must be integrated into an overall protective function from tissue iron overload toxicity. GH, growth hormone CD8T, subpopulation of T lymphocytes CD8CD28, subpopulation of TCD8+ lymphocytes HFE, non-classical MHC class I gene C282Y and H63D, HFE mutations TfR, transferrin receptor pS61ck, kinase of importance in T cell activation, whose activity is diminished in CD8-I- cells in HH patients [36] DCTl, iron transporter gene.

While several models of Cr(III) pharmacokinetics in mammals have been developed (111, 430, 502), little is known about Cr(III) speciation in organisms. Transferrin, a major transport protein for many metal ions (503), is likely to be the main Cr(III) carrier in blood (504). Although iron transport is a primary function of transferrin, the strength of its binding to Cr(HI) is comparable to that for Fe(III) (45, 505) and Cr -transferrin complexes [unlike for the complexes of Mn(II), Cu(n), or Zn(II)] mimic those of Fe(III) in interactions with cell transferrin receptors (506). Preliminary results of X-ray absorption spectroscopic studies suggest that Cr(lll) may occupy the same sites in the transferrin protein as Fe(lll) (507). 

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