title: Vesicular transport of fe and interaction with other metal ions in polarized Caco2 cell monolayers.
abstract: Two aspects of the mechanisms by which iron is absorbed by the intestine were studied in the Caco2 cell model, using 59Fe(II)-ascorbate. Data showing the importance of vesicular processes and cycling of apotransferrin (apoTf) to uptake and overall transport of Caco2 cell monolayers (or basolateral 59Fe release) were obtained by comparing effects of: a) adding apoTf to the basal chamber; b) adding vesicular transport inhibitors; or c) cooling to 4 degrees C. These showed that apoTf may be involved in as much as half of Fe transfer across the basolateral membrane, and that vesicular processes may also play a role in non-apoTf-dependent Fe transport. Studies were initiated to examine potential interactions of other metal ions with Fe(II) via DMT1. Kinetic data showed a single, saturable process for uptake of Fe(II) that was pH dependent and had a Km of 7 microM. An excess of Mn(II) and Cu(I) over Fe(II) of 200: 1 (microM: microM) in 1 mM ascorbate markedly inhibited Fe uptake. The kinetics were not competitive. Km increased and Vmax decreased. We conclude that vesicular transport, involving endo- and exocytosis at both ends of the enterocyte, is a fundamental aspect of intestinal iron absorption and that DMT1 may function as a transporter not just for divalent but also for monovalent metal ions.
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Fullerton, California 92834-6866, USA. mlinder@fullerton.edu
authors.forename: Maria C
authors.initials: MC
authors.lastname: Linder
authors.forename: Mizue
authors.initials: M
authors.lastname: Moriya
authors.forename: Anne
authors.initials: A
authors.lastname: Whon
authors.forename: Azeb
authors.initials: A
authors.lastname: Kassa
authors.forename: Cynthia
authors.initials: C
authors.lastname: Gilley
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000493:pharmacokinetics*; D001205:Ascorbic Acid / Q000493:pharmacokinetics*; D001693:Biological Transport, Active; D018938:Caco-2 Cells / Q000378:metabolism; D027682:Cation Transport Proteins / Q000493:pharmacokinetics*; D004347:Drug Interactions; D004705:Endocytosis; D005296:Ferrous Compounds / Q000493:pharmacokinetics*; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D051381:Rats; D014168:Transferrin / Q000493:pharmacokinetics*; D033921:Vesicular Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D001059:Apoproteins; D001205:Ascorbic Acid; D027682:Cation Transport Proteins; D005296:Ferrous Compounds; D014168:Transferrin; D033921:Vesicular Transport Proteins; D000099236:Solute Carrier Family 11, Member 2; C028284:apotransferrin; C051140:iron(II)-ascorbic acid complex