title: Influence of alpha-linked glucose on sodium-glucose cotransport activity along the small intestine in cattle.
abstract: Thirteen steers (378+/-23 kg) were used in a split-plot experimental design to evaluate the effect of small intestinal carbohydrate on sodium-glucose cotransport in brush border membrane vesicles prepared from five equidistant sites along the small intestine. The steers consumed 7.2+/-0.4 kg/d ground fescue hay and soybean meal-based supplement and were infused ruminally or postruminally with a partial alpha-amylase starch hydrolysate (914.5+/-8.3 g/d) for 7 d. On d 7, five equidistant 1-m small intestinal sections were harvested and frozen in liquid N for later preparation of brush-border membrane vesicles. Maltase activity of the homogenate and vesicle preparations changed (P < 0.001; lowest in the duodenum, highest in the jejunum) and alkaline phosphatase decreased (P < 0.001) along the small intestine. With respect to the original homogenates, the vesicle preparations were enriched 9.80+/-0.83- and 7.64+/-0.67-fold for alkaline phosphatase and maltase, respectively; enrichments were not different between treatments (P = 0.76 and 0.39, respectively). However, alkaline phosphatase and maltase enrichment changed (P < 0.001) along the small intestine. Recoveries of alkaline phosphatase and maltase activities (25.0+/-0.2% and 19.5+/-0.2%, respectively) in the vesicle preparation were not affected (P = 0.29 and 0.21, respectively) by treatment but changed (P < 0.001) along the intestine. Recovery of protein in the vesicle preparation was 2.60+/-0.01% and was not affected by treatment or intestinal site. Sodium-glucose cotransport activity (220+/-44 pmol x mg(-1) x s(-1)) was not affected (P = 0.34) by treatment but did change (P < 0.001; lowest in the ileum, highest in the proximal and mid-jejunum) along the small intestine. Apparent Km of the sodium-glucose cotransporter for glucose was 62.8+/-5.8 microM. The specific activity of maltase was highest in the jejunum, and sodium-glucose cotransport was highest in the first two jejunal sites. However, duodenal maltase activity was lowest and ileal sodium-glucose cotransport activity was lowest. Sodium-glucose cotransport activity may limit small intestinal starch assimilation in the distal small intestine. It does not seem that glucose arising from carbohydrate hydrolysis regulates activity of sodium-dependent glucose transport in cattle.
authors.affiliation: Department of Animal Sciences, University of Kentucky, Lexington 40546-0215, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Bauer
authors.forename: D L
authors.initials: DL
authors.lastname: Harmon
authors.forename: D W
authors.initials: DW
authors.lastname: Bohnert
authors.forename: A F
authors.initials: AF
authors.lastname: Branco
authors.forename: G B
authors.initials: GB
authors.lastname: Huntington
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D002149:Energy Intake; D005947:Glucose / Q000494:pharmacology*; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000187:drug effects*; D000520:alpha-Glucosidases / Q000378:metabolism
chemical_list: D009004:Monosaccharide Transport Proteins; D000469:Alkaline Phosphatase; D000520:alpha-Glucosidases; D005947:Glucose