Copper in Drinking Water (2000) / Chapter Skim
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2 Physiological Role of Copper
2 Physiological Role of Copper
Pages 16-32
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From page 16... ...
Severe copper deficiencies, either gene defects due to mutations or low dietary copper intakes, although relatively rare in humans, have been linked to mental re 16
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From page 17... ...
As a result of complexing with amino acids, organic acids, or other chelators, a high fraction of copper is soluble in the intestinal tract. Studies on isolated segments of the duodenum suggest that copper ions enter into the mucosal cells lining the intestine by simple diffusion and exit at the basolateral surface by a different mode of transport (Bremner 1980~.
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From page 18... ...
Thus, factors besides ceruloplasmin are required for biliary copper excretion and for maintaining normal liver copper homeostasis in the liver. A clue to the identity of such factors has come from studies of lipofuschinlike granules that accumulate in the liver of patients who suffer from primary biliary cirrhosis and are unable to excrete copper.
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From page 19... ...
The rapid up iIt is important to distinguish between free copper ions and copper as a complex with amino acid or other biocompounds. Solubility considerations suggest that copper as the free metal exists at extremely low concentrations in the cell cytosol.
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From page 20... ...
In general, chemical form, valence state, and relative concentrations of competing metals influence the quantity of copper that is absorbed. Select amino acids such as histidine and glutamine (Harris and Sass-Kortsak 1967)
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From page 21... ...
The intravenous dose allows for an estimation of the endogenous excretion into the gut. Retention from oral intake as estimated from copper in the feces was shown to be highest when dietary copper concentrations were lowest: 67% at 0.38 mg per day, 54% at 0.66 mg per day, and 44% at 2.49 mg per day (Turnlund et al.
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From page 22... ...
The liver receives copper from the intestine via the portal circulation and redistributes the copper to the tissue via ceruloplasmin, albumin, and amino acids. Nearly half of the copper consumed is not absorbed and passes into the feces.
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From page 23... ...
Little information is available on dietary copper absorption, or copper retention, in toddlers and young children. Dietary and Other Interactions Early research with whole animals showed that the rate and amount of copper ions transferred across intestinal epithelia were influenced positively by dietary amino acids, but negatively by ascorbate and competing metal ions (Bremner 1980; Hogan and Rauser 1981; L'Abbe and Fischer 1984; Oestreicher and Cousins 1985; Fields et al.1986~.
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From page 24... ...
The influence of fructose on copper balance in humans has not been well defined. Based on studies in rats, ascorbic acid is thought to lower plasma and liver copper levels by reducing copper absorption, and the reduced copper absorption later stimulates copper absorption and depresses biliary excretion (Van den Berg et al.
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From page 25... ...
On the other hand, complexes of copper with other amino acids and organic acids might result in similar bioavailability to that of soluble copper sulfate ~7apnir 1998~. Based on studies to date, zinc is the primary mineral, and dietary element, which affects copper absorption.
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From page 26... ...
Particular emphasis should be given to the investigation of metal response elements on copper transport proteins. Research is needed to determine the ontogeny of copper transporters.
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From page 27... ...
1997. Isolation of a cDNA encoding the human homolog of COX17, a yeast gene essential for mitochondrial copper recruitment.
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From page 28... ...
1994b. The Saccharomyces cerevisiae copper transport protein (Ctrlp)
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From page 29... ...
1967. The influence of amino acids on copper uptake by rat liver slices.
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1985. Copper absorption from human milk, cow's milk, and infant formulas using a suckling rat model.
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From page 31... ...
1995. Copper uptake by cultured trophoblast cells isolated from human term placenta.
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From page 32... ...
1994. Ascorbic acid feeding of rats reduces copper absorption, causing impaired copper status and depressed biliary copper excretion.
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