Nonlinear intestinal absorption of (1-->3)-beta-D-glucan caused by absorptive and secretory transporting system.
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.
Tomita
Mikio
M
Department of Drug Absorption and Pharmacokinetics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences.
Miwa
Mitsutaka
M
Ouchi
Shohei
S
Oda
Toshio
T
Aketagawa
Jun
J
Goto
Yuko
Y
Hayashi
Masahiro
M
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*
D005936:Glucans; D011134:Polysaccharides; D011509:Proteoglycans; D047071:beta-Glucans; C010770:polysaccharide-K; C008247:laminaran; D019297:2,4-Dinitrophenol