Intestinal Na+/glucose cotransporter-mediated transport of glucose conjugate formed from disaccharide conjugate

Intestinal absorption of beta-disaccharide (cellobiose, maltose and lactose) conjugates of p-nitrophenol (p-nitrophenyl beta-disaccharide) were examined in terms of the hydrolysis of disaccharide conjugate to monosaccharide conjugate and the transport of monosaccharide conjugate by Na+/glucose transport carrier (SGLT1). beta-Cellobioside, beta-maltoside and beta-lactoside of p-nitrophenol (p-NP) were hydrolyzed to p-nitrophenyl beta-glucoside (p-NP beta glc) on the mucosal side, and p-NP beta glc appeared on the serosal side. Although p-NP beta-disaccharide, p-NP and p-NP glucuronide also appeared on the serosal side, their amounts were much lower than that of p-NP beta glc. The amount of p-NP beta glc transported to the serosal side was decreased in the presence of phloridzin (transport inhibitor of SGLT1) and in the absence of Na+ (a cosubstrate of SGLT1), indicating that p-NP beta glc was formed from p-NP beta-disaccharide on the mucosal side and transported to the serosal side by SGLT1. Furthermore, the absorption clearance of p-NP beta glc, which was formed from p-NP beta-cellobioside and p-NP beta-lactoside by lactase-phloridzin hydrolase (LPH), was much higher than that of p-NP beta glc itself, although the absorption clearance of p-NP beta glc, which was formed from p-NP beta-maltoside by maltase was similar to that of p-NP beta glc itself. These results indicated that p-NP beta glc was transported by the vectorial cooperation of SGLT1 with LPH from mucosal p-NP beta-cellobioside or p-NP beta-lactoside. (C) 1998 Elsevier Science B.V.