GALACTOSE-CONTAINING CARBOHYDRATES ARE PREFERENTIALLY ABSORBED IN THENEONATAL PIG COLON

Previous studies on the piglet colon in newborns cleared of bacterial metabolic activity showed a capacity for lactose absorption. Colonic a bsorption occurred at a flux rate equal to the assimilation of lactose by the small intestine but by a process that did not involve either g lucose-galactose sodium cotransport or simple diffusion. Surprisingly, colonic lactose transport did not require either fermentation or clea vage of the disaccharide for uptake. Experiments were designed to test the selectivity of the colonic transport process for a variety of car bohydrates. Colonic tissues from 4-7-d-old piglets were mounted in Uss ing chambers and the mucosal-to-serosal flux of radiolabeled carbohydr ates was compared with that of lactose. The results showed a 3-4-fold greater flux of galactose-containing sugars as compared with glucose-c ontaining carbohydrates at concentrations up to 40 mM. Even lactulose, a synthetic disaccharide assumed to require bacterial digestion befor e assimilation, was transported readily. N-Acetylgalactosamine, a comp onent of colonic mucus, inhibited the flux of lactose, whereas N-acety lglucosamine did not. Similarly, lactosylated BSA inhibited lactose fl ux, whereas nonlactosylated BSA did not. The capacity of the colon of the newborn to differentiate moieties as similar as glucose and galact ose suggests an absorptive process for carbohydrates with a high degre e of discrimination.