Hamster intestinal disaccharide absorption: extracellular hydrolysis precedes transport of the monosaccharide products.
Hydrolase-related transport was re-investigated in hamster small intestine by the tissue accumulation method. The Na+-dependent, phlorizin-sensitive monosaccharide transport system saturates with 30 mM-D-glucose. According to the hydrolase-related transport hypothesis, additional glucose units will be taken up if they are given in the form of a disaccharide susceptible to hydrolysis. But in experiments with [14C]sucrose we found no evidence for any such surplus glucose uptake. The uptake of 14C label from sucrose was abolished by using Tris, a strong inhibitor of sucrase, by adding competitive inhibitors of the D-glucose transport system (D-glucose, beta-methyl-D-glucopyranoside or phlorizin), and by substituting Li+ for the Na+ in the incubation medium. Glucose and fructose derived from sucrose did not enter the tissues in equimolar amounts: the glucose moiety was taken up much faster. We conclude that in hamster intestine there is no evidence for the existence of hydrolase-related transport with sucrose as the monosaccharide donor. The enzymatic hydrolysis of sucrose and the transport of its products, glucose and fructose, are two distinct events, acting sequentially.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002250:Carbon Radioisotopes; D006224:Cricetinae; D005110:Extracellular Space / Q000378:metabolism; D005632:Fructose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006867:Hydrolases / Q000378:metabolism*; D006868:Hydrolysis; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000201:enzymology / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000201:enzymology; D010695:Phlorhizin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013393:Sucrase / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism*
D002250:Carbon Radioisotopes; D005632:Fructose; D013395:Sucrose; D012964:Sodium; D010695:Phlorhizin; D006867:Hydrolases; D013393:Sucrase; D005947:Glucose