title: Nonlinear intestinal absorption of (1-->3)-beta-D-glucan caused by absorptive and secretory transporting system.
abstract: The mechanism of the nonlinear concentration dependence of intestinal absorption of (1-->3)-beta-D-glucan was studied using in situ rat intestinal perfusion, as well as the in vitro Ussing-type chamber method mounted with rat intestinal tissue. The intestinal absorption rate constant of a (1-->3)-beta-D-glucan, laminaran, evaluated by the loop method increased significantly with increasing concentration of laminaran up to 0.5 muM in a nonlinear fashion and tended to decrease at higher concentrations. Mucosal-to-serosal directed permeation of the laminaran across rat ileal sheets evaluated by the in vitro Ussing-type chamber method also decreased in a dose-dependent fashion. Serosal-to-mucosal directed permeation decreased in a concentration-dependent manner. In addition, the serosal-to-mucosal flux was reduced in the presence of metabolic inhibitor, 2,4-di-nitrophenol. These results suggest that laminaran is secreted into the intestinal lumen predominantly by the efflux transporting system. We conclude that intestinal transport of (1-->3)-beta-D-glucan involves specialized transporter or something similar in both absorptive and secretory directions, and complex nonlinear intestinal absorption characteristics can be ascribed to the participation of multiple transport mechanism.
authors: Department of Drug Absorption and Pharmacokinetics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences.
authors: Mikio
authors: M
authors: Tomita
authors: Mitsutaka
authors: M
authors: Miwa
authors: Shohei
authors: S
authors: Ouchi
authors: Toshio
authors: T
authors: Oda
authors: Jun
authors: J
authors: Aketagawa
authors: Yuko
authors: Y
authors: Goto
authors: Masahiro
authors: M
authors: Hayashi
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D004305:Dose-Response Relationship, Drug; D005936:Glucans; D007082:Ileum / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D017711:Nonlinear Dynamics; D011134:Polysaccharides / Q000008:administration & dosage / Q000493:pharmacokinetics*; D011509:Proteoglycans; D051381:Rats; D017208:Rats, Wistar; D012704:Serous Membrane / Q000187:drug effects / Q000378:metabolism*; D047071:beta-Glucans / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D005936:Glucans; D011134:Polysaccharides; D011509:Proteoglycans; D047071:beta-Glucans; C010770:polysaccharide-K; C008247:laminaran; D019297:2,4-Dinitrophenol