title: Sugar absorption and secretion by winter flounder intestine.
abstract: Transport of sugars by winter flounder (Pseudopleuronectes americanus) intestine has been examined, and the following observations have been made. 1) No net absorption of D-galactose was found in controls; however, mucosally applied 0.1 mM phlorizin stimulated the mucosal-serosal flux with net sugar secretion. 2) Net absorption of methyl glycosides was inhibited by D-galactose, 0.1 mM ouabain, and phlorizin (without induction of secretion). 3) Net secretion of 2-deoxy-D-galactose was found without cellular accumulation of free sugar. The secretory process had a Km of 10 mM and was inhibited by serosally applied 0.1 mM phloretin, bilateral replacement of Ringer Na+ by choline, serosal ouabain, and D-galactose. 4) No net absorption or secretion of 2-deoxy-D-glucose was found with a variety of experimental conditions. 5) At least two active transport systems for sugars appear to be operative in the flounder intestine: a conventional Na+-dependent sugar transport system across the brush border that allows net absorption and a Na+-dependent secretory system that apparently also operates across the mucosal border. Because D-galactose is transported by both systems, there is no net flux of this sugar. Several possible models for the net secretory system are discussed.
mesh_terms: D000818:Animals; D050260:Carbohydrate Metabolism; D003847:Deoxyglucose / Q000378:metabolism; D005399:Fishes / Q000378:metabolism*; D005643:Fucose / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D006571:Heterocyclic Compounds / Q000494:pharmacology; D007097:Imines / Q000494:pharmacology; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism; D008759:Methylglycosides / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D010693:Phloretin / Q000494:pharmacology; D010695:Phlorhizin / Q000494:pharmacology; D012964:Sodium / Q000502:physiology
chemical_list: D006571:Heterocyclic Compounds; D007097:Imines; D008759:Methylglycosides; D005643:Fucose; D010042:Ouabain; C014925:RMI 12330A; D003847:Deoxyglucose; D012964:Sodium; D010695:Phlorhizin; D010693:Phloretin; D005690:Galactose