Journal of Animal Science, Vol 79, Issue 7 1917-1924, Copyright © 2001 by American Society of Animal Science

JOURNAL ARTICLE

Influence of alpha-linked glucose on sodium-glucose cotransport activity along the small intestine in cattle

M. L. Bauer, D. L. Harmon, D. W. Bohnert, A. F. Branco and G. B. Huntington
Department of Animal Sciences, University of Kentucky, Lexington 40546-0215, USA.

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.

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