Nonlinear Intestinal Absorption of Fluorescein Isothiocyanate Dextran 4, 000 Caused by Absorptive and Secretory Transporting System

Mikio Tomita, Rie Ohkubo, Shohei Ouchi, Chise Kawahata, Masahiro Hayashi
2011 Pharmacology and Pharmacy  
The mechanism of the nonlinear concentration dependence of the intestinal absorption of fluorescein isothiocyanate dextran 4,000 (FD-4) was studied using in situ rat intestinal loops and the in vitro Ussing-type chamber method. The intestinal absorption rate constant of FD-4, as evaluated by the intestinal loop method, increased significantly in a nonlinear fashion as the FD-4 concentration increased up to 0.2 mM and tended to decrease at concentrations higher than 0.2 mM. The
more » ... e mucosal-to-serosal permeation of FD-4 across rat ileal sheets, as evaluated by the in vitro Ussing-type chamber method, also increased in a nonlinear fashion in the low concentration range (0.01 -0.02 mM), before decreasing as the concentration increased further, whereas serosal-to-mucosal permeation decreased in a concentration-dependent manner. In addition, mucosal-to-serosal flux and serosal-to-mucosal flux were increased and reduced in the presence of the metabolic inhibitor 2,4-dinitrophenol, respectively. These results suggest that FD-4 is predominantly secreted into the intestinal lumen by an efflux transport system. [25] M. Tomita, M. J. Menconi, R. L. Dekude, et al., "Polarized Transport of Hydrophilic Compounds across Rat Colonic Mucosa from Serosa to Mucosa is Temperature
doi:10.4236/pp.2011.23025 fatcat:resbx35tmffkrf2hftsjys63pu