title: Na(+)-dependent transport of D-xylose by bovine intestinal brush border membrane vesicles (BBMV) is inhibited by various pentoses and hexoses.
abstract: To detect whether pentoses and hexoses occurring in rumen bacteria or in hemicellulose ingested with feed and partly released in the small intestine have an affinity for the Na(+)-dependent glucose transporter of the bovine intestinal brush border membrane (BBM), we investigated whether these monosaccharides inhibit Na(+)-dependent transport of 14C-labelled D-xylose across the BBM using brush border membrane vesicles (BBMV) isolated from the mid-jejunum of cows. We used D-xylose as the transport substrate, because it has a low affinity for the Na(+)-dependent glucose transporter and thus its uptake into BBMV is more efficiently competitively inhibited by other sugars than that of D-glucose. D-Ribose, D-mannose and L-rhamnose occurring in rumen bacteria significantly inhibited Na(+)-dependent uptake of D-xylose into BBMV, but their inhibitory effect was less than that of D-glucose, D-xylose and phlorizin. This also applied to L-arabinose (and D-arabinose), which is, like D-xylose and D-galactose, a constituent of hemicellulose, and to 2-deoxy-D-glucose. Of all monosaccharides tested, only D-fructose did not affect Na(+)-dependent D-xylose transport. It is concluded that some pentoses and hexoses occurring in rumen bacteria (D-ribose, D-mannose and L-rhamnose) or hemicellulose (L-arabinose and D-xylose) have a low affinity for the Na(+)-dependent glucose transporter of the bovine BBM and may therefore be absorbed from the jejunum when released in the small intestine.
authors.affiliation: Institute of Veterinary Physiology, University of Zurich, Winterthurerstr. 260, CH-8057, Zurich, Switzerland. scharrer@vetphys.unizh.ch
authors.forename: E
authors.initials: E
authors.lastname: Scharrer
authors.forename: B
authors.initials: B
authors.lastname: Grenacher
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001693:Biological Transport, Active; D002417:Cattle / Q000378:metabolism*; D006601:Hexoses / Q000494:pharmacology*; D007583:Jejunum / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000187:drug effects*; D010429:Pentoses / Q000494:pharmacology*; D014994:Xylose / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D006601:Hexoses; D009004:Monosaccharide Transport Proteins; D010429:Pentoses; D014994:Xylose