title: Mobilisation of recently absorbed 59Fe in ex vivo perfused rat duodena and the influence of iron status and subsequently absorbed chelators.
abstract: To investigate the effect of subsequently absorbed metal chelators on recently absorbed 59Fe, duodenal segments from iron-deficient and iron-adequate rats were perfused ex vivo until the 59Fe tissue load had reached a steady state. Subsequently, the segments were perfused with 3 model chelators and their iron complexes: nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and citrate. Of these, NTA and EDTA bind iron much tighter than citrate, and Fe-NTA complexes exchange iron within seconds while Fe-EDTA complexes need 48 h to reach equilibrium. Duodenal mucosa-to-serosa transport rates were comparable for all 3 chelators and correlated linearly with luminal concentration. Subsequent perfusion with increasing NTA, Fe-NTA(1:2) and EDTA concentrations mobilised increasing amounts of 59Fe from the duodenum. Mobilised 59Fe moved preferentially back into the luminal perfusate in iron-adequate segments. In iron-deficient segments, 59Fe preferentially continued the absorption process across the basolateral membrane. Fe-EDTA(1:1) hardly mobilised any 59Fe back into the lumen, though basolateral transfer increased at high concentrations. Citrate and Fe-citrate(1:1) mobilised 59Fe only at very high concentrations. This behaviour is in accordance with the rules of complex chemistry: strong, fast reacting ligands like NTA show most impact. Slowly reacting complexes like Fe-EDTA(1:1) have little mobilising impact in spite of strong affinity between EDTA and iron. The low affinity between iron and citrate can be compensated by large concentration. Moreover, iron-deficient segments show stronger re-uptake of mobilised 59Fe from the lumen and a stronger transfer of 59Fe from the tissue across the basolateral membrane. Both are compatible with the more marked expression of divalent metal transporter 1 (DMT-1) and IREG-1 at the brushborder and basolateral membrane of iron-deficient enterocytes. The data suggest that iron ions interact with food ligands during their passage from the apical to the basolateral side of duodenal enterocytes.
authors.affiliation: Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Fachgebiet Tierernährung und Leistungsphysiologie, Technische Universität München, Hochfeldweg 6, D-85350 Freising, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ettle
authors.forename: Bernd
authors.initials: B
authors.lastname: Elsenhans
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Windisch
authors.forename: Surjit K S
authors.initials: SK
authors.lastname: Srai
authors.forename: Klaus
authors.initials: K
authors.lastname: Schümann
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002951:Citrates / Q000378:metabolism; D004386:Duodenum / Q000033:anatomy & histology / Q000378:metabolism*; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000502:physiology*; D007502:Iron Chelating Agents / Q000378:metabolism*; D007504:Iron Radioisotopes / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002951:Citrates; D007502:Iron Chelating Agents; D007504:Iron Radioisotopes