Copper duodenal

Once inside the mucosal cell, iron then has to be transported across the membrane to serum transferrin. This appears to take place via the Iregl transporter protein (also known as ferroportin 1 or MTPl). Iregl is a transmembrane protein located at the basolateral membrane of the cell that has been shown to be involved in iron uptake. Oxidation of Iregl-bound ferrous iron and its release to transferrin is likely to be enhanced by the membrane-bound multicopper ferroxidase hephaestin. This protein is 50% identical to ceruloplasmin, a soluble protein identified as having a possible role in iron loading of transferrin see Copper Proteins Oxidases). Mutation of hephaestin in mice leads to a build up of iron in duodenal cells and overall iron deficiency in the body. ... 

Given the eflFects of ascorbic acid on the absorption of iron and copper, investigators have been interested in possibly significant interactions with zinc. The absorption of zinc and other divalent mineral ions was studied using an isolated, filled duodenal loop in situ in the rat (58). A lO -M zinc solution was infused in the presence or absence of 10" M ascorbate or dehydroascorbate. A two-thirds reduction in the... 

Maintenance and repair of duodenal and gastric collagen and elastin connective tissue components also seems to be an important copper-dependent enzyme function in preventing or repairing duodenal or gastric ulcers. Induction or facilitation of de novo synthesis of lysyl oxidase by copper complexes [16] merits consideration to account for the observed rapid and normal replacement of connective tissue components in the surgically placed gastric ulcer model [178]. 

We now turn to the question of how copper may be directly involved in iron metabolism, relying on the comprehensive paper of Lee et al, 40) which reports an in vivo study on iron metabolism in copper-deficient swine. They found evidence for abnormalities of iron metabolism at four major sites the duodenal mucosa, the reticuloendothelial system (R-E), the hepatic parenchymal cells, and the normoblasts. For the first three tissues, each of which can concentrate, store, and release iron, copper deficiency leads to an impairment in the release of iron. 

Copper is resorbed mainly in the duodenal part of the digestive tract of man. The degree of resorption is estimated at between 25 and 70%. Resorption of copper depends on the current saturation of the organism (its deficit leads to a higher degree of resorption). As a binding agent, metallothionein may play a role in the intake of copper by intestinal epithelial cells. The resorption of copper is achieved by two mechanisms active transport, which prevails in the copper deficit in the body, and simple diffusion. Copper is excreted from the body primarily via the faeces, while the majority of the resorbed copper is excreted in the bile. If the daily dose of copper received in diet is approximately 2.5 mg, the amount resorbed into the blood circulation is about 1.2 mg. At the same time the hver eliminates in one day, via the bile, about 0.8-0.9 mg of copper into the intestine, and the kidney excretes about 0.1 mg of copper in urine. The real total daily intake of copper by the body is then only 0.2-0.3 mg, which is about 10% of the copper that is resorbed. 

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