EFFECTS OF VARYING LEVELS OF DUODENAL OR MIDJEJUNAL GLUCOSE AND 2-DEOXYGLUCOSE INFUSION ON SMALL-INTESTINAL DISAPPEARANCE AND NET PORTAL GLUCOSE FLUX IN STEERS

Six crossbred steers (261 +/- 18 kg BW) fitted with hepatic portal, me senteric venous and arterial catheters, and duodenal, midjejunal, and ileal cannulas were used in a replicated 3 x 3 Latin square design to determine the effect of varying levels and site of glucose plus 2-deox yglucose (2DG) infusion on net portal-drained visceral flux. Steers we re fed chopped alfalfa in six equal portions daily at 1.5% of BW. Gluc ose (0, 9, or 18 g/h) and 2DG (0, 1, or 2 g/h) were infused continuous ly through the duodenal or midjejunal cannula (two infusion sites) at total glucose plus 2DG infusion rates of 0, 10, or 20 g/h. Arterial an d portal blood samples were taken simultaneously at 20-min intervals f rom 5 to 9 h of infusion. Portal blood flow was determined by continuo us infusion of p-aminohippurate and net flux was calculated as venous- arterial concentration (PA) difference difference of glucose and 2DG w ere greater (P <.05) times blood flow. Arterial concentration of gluco se was not affected (P >.10) by glucose plus 2DG infusion, whereas art erial concentration of 2DG was greater (P <.05) when glucose plus 2DG was infused into the duodenum and increased (linear, P <.10) as amount of glucose plus 2DG infused into both the duodenum and midjejunum inc reased. Net portal flux and PA when glucose plus 2DG was infused into the duodenum. Although 2DG was infused at 10% of the total glucose plu s 2DG infusion, it accounted for only 1.7 and .7% of the glucose plus 2DG appearing in portal blood when glucose plus 2DG was infused at 10 and 20 g/h, respectively. We conclude that glucose is more readily abs orbed across the proximal-half than the distal-half of the small intes tine, and that passive diffusion is a minor route of glucose absorptio n.