Enhancement of colonic drug absorption by the transcellular permeation route.

The effects of sodium caprate and sodium caprylate on transcellular permeation routes were examined in rats. The release of membrane phospholipids was significantly increased only by caprate, while protein release did not change from the control in the presence of caprate or caprylate, indicating that the extent of membrane disruption was insufficient to account for enhanced permeation. Using brush border membrane (BBM) vesicles prepared from colon, with their protein and lipid component labeled by fluorescent probes, the perturbing actions of caprate and caprylate toward the membrane were examined by fluorescence polarization. Caprate interacted with membrane protein and lipids, and caprylate mainly with protein, causing perturbation to the membrane. The release of 5(6)-carboxyfluorescein previously included in BBM vesicles was increased by caprate but not by caprylate. These results suggest that caprate enhances permeability via the transcellular route through membrane perturbation.