title: Characteristics of (+)-catechin and (-)-epicatechin transport across pig intestinal brush border membranes.
abstract: OBJECTIVE
  (+)-Catechin and (-)-epicatechin are considered as disease preventive flavan-3-ols of foods like fruits, beverages and chocolate. We investigated mechanisms and kinetics of (+)-catechin and (-)-epicatechin uptake employing a validated in vitro model with isolated pig brush border membrane vesicles.
  
  
  METHODS
  Vesicles were isolated from pig small intestine employing the divalent cation method. Characterization (marker enzymes, electron microscopy) confirmed their purity and function. Transport studies with (+)-catechin and (-)-epicatechin under predefined conditions [presence/absence of sodium, pH gradient, temperature (8-37 degrees C), various initial substrate concentrations (2-20 mmol/l)] revealed a measurable transport (HPLC analyses) across the brush border membrane for both substrates.
  
  
  RESULTS
  Catechin transport was stimulated by an outwardly directed H(+) gradient (pH(i) 5.5/pH(o) 7.5). The presence of an inwardly directed Na(+) gradient did not result in a transient overshoot in (+)-catechin and (-)-epicatechin uptake. At 37 degrees C, subtraction of diffusion from the total transport rate showed saturation kinetics.
  
  
  CONCLUSIONS
  Our in vitro study indicate that both (+)-catechin and (-)-epicatechin are transported across the basolateral membrane using a dual transport system consisting of free diffusion (dominant at low concentrations) and carrier-mediated facilitated diffusion.
authors.affiliation: Department of Nutrition and Food Sciences, University of Bonn, Bonn, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Starp
authors.forename: Birgit
authors.initials: B
authors.lastname: Alteheld
authors.forename: Peter
authors.initials: P
authors.lastname: Stehle
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002392:Catechin / Q000493:pharmacokinetics*; D002414:Cations, Monovalent; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D007408:Intestinal Absorption / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism* / Q000648:ultrastructure; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013552:Swine; D013696:Temperature
chemical_list: D002414:Cations, Monovalent; D012965:Sodium Chloride; D011189:Potassium Chloride; D002392:Catechin