title: Mechanisms of dietary Cu uptake in freshwater rainbow trout: evidence for Na-assisted Cu transport and a specific metal carrier in the intestine.
abstract: Copper (Cu) is both a vital nutrient and a potent toxicant. The objective of this study was to analyze the mechanistic nature of intestinal Cu transport in rainbow trout using radiolabeled Cu (64Cu) and an in vitro gut sac technique. Reduction of mucosal NaCl levels inhibited Cu transport while increase caused stimulation; Na(2)SO(4) had an identical effect, implicating Na(+) rather than the anion. These responses were unrelated to solvent drag, osmotic pressure or changes in transepithelial potential. The presence of elevated luminal Ag stimulated Cu and Na(+) uptake. Phenamil caused a partial inhibition of both Cu and Na(+) uptake while hypercapnia stimulated Na(+) and Cu transport. Cu uptake was sensitive to luminal pH and inhibited by a tenfold excess of Fe and Zn. These factors had no effect on Na(+ )uptake. On the basis of these results we propose a novel Na(+)-assisted mechanism of Cu uptake wherein the Na(+) gradient stimulates an increase in the H(+) concentration of the brushborder creating a suitable microenvironment for the effective transport of Cu via either DMT1 or Ctr1.
authors.affiliation: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S4K1. nadellsr@mcmaster.ca
authors.forename: Sunita Rao
authors.initials: SR
authors.lastname: Nadella
authors.forename: Martin
authors.initials: M
authors.lastname: Grosell
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002712:Chlorides / Q000493:pharmacokinetics; D003300:Copper / Q000493:pharmacokinetics*; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D012834:Silver / Q000494:pharmacology; D012964:Sodium / Q000493:pharmacokinetics*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013431:Sulfates / Q000494:pharmacology
chemical_list: D002712:Chlorides; D026941:Sodium Channel Blockers; D013431:Sulfates; C012036:sodium sulfate; D002245:Carbon Dioxide; C047088:phenylamil; D012834:Silver; D003300:Copper; D000584:Amiloride; D012964:Sodium