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.