Xiaojuan Tian1, Xiaoda Yang, Kui Wang, Xiuwei Yang. 1. Department of Chemical Biology and State Key laboratories of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100083, People's Republic of China.
Abstract
PURPOSE: In this study, we chose three of the flavonoids isorhamnetin-3-O-rutinoside(IRR) diosmetin-7-O-beta-D-xylopyranosyl-(1-6)-beta-D-glucopyranoside(DXG) and morin, which showed obvious efflux, to test the hypothesis that a specific efflux transporter is responsible for their transportation. METHODS: The intestinal epithelial membrane transport of the flavonoids were examined using the monolayer of the human Caco-2 cell line grown in Transwells, a common model of intestinal absorption. The flavonoids were measured by high performance liquid chromatography with UV detector. RESULT: The efflux of morin, IRR and DXG, across Caco-2 cell monolayers was examined over the concentration range from 2 to 200 microM and showed a saturable process. The depletion of the cellular ATP stores with 5 mM iodoacetamide led to a significant inhibition of the efflux. Fifty micromolar verapamil, a chemical inhibitor of P-glycoprotein, had no effect on the transport of the three flavonoids, while the presence of 50 microM MK-571 and 1 mM probenecid, MRP inhibitors, resulted in an obvious reduction in the efflux. Moreover, inhibition of morin transport by MK-571 demonstrated concentration dependence. The transportation of the three flavonoids was compared with apigenin. CONCLUSION: These data support a role for MRPs in the intestinal transcellular efflux of morin, IRR, DXG and possibly other hydrophilic flavonoid aglycons and glycosides.
PURPOSE: In this study, we chose three of the flavonoidsisorhamnetin-3-O-rutinoside(IRR) diosmetin-7-O-beta-D-xylopyranosyl-(1-6)-beta-D-glucopyranoside(DXG) and morin, which showed obvious efflux, to test the hypothesis that a specific efflux transporter is responsible for their transportation. METHODS: The intestinal epithelial membrane transport of the flavonoids were examined using the monolayer of the human Caco-2 cell line grown in Transwells, a common model of intestinal absorption. The flavonoids were measured by high performance liquid chromatography with UV detector. RESULT: The efflux of morin, IRR and DXG, across Caco-2 cell monolayers was examined over the concentration range from 2 to 200 microM and showed a saturable process. The depletion of the cellular ATP stores with 5 mM iodoacetamide led to a significant inhibition of the efflux. Fifty micromolar verapamil, a chemical inhibitor of P-glycoprotein, had no effect on the transport of the three flavonoids, while the presence of 50 microM MK-571 and 1 mM probenecid, MRP inhibitors, resulted in an obvious reduction in the efflux. Moreover, inhibition of morin transport by MK-571 demonstrated concentration dependence. The transportation of the three flavonoids was compared with apigenin. CONCLUSION: These data support a role for MRPs in the intestinal transcellular efflux of morin, IRR, DXG and possibly other hydrophilic flavonoid aglycons and glycosides.