2002 年 25 巻 12 号 p. 1608-1613
The aims of this study were to examine the enhancing effects of aloe-emodin anthrone (AEA) on the colonic membrane permeability of water-soluble and poorly permeable compounds and to clarify the mechanism of the permeation-enhancing activity of AEA. The permeation-enhancing activity of AEA was estimated from changes in the permeability coefficient of 5(6)-carboxyfluorescein (CF) in rat colonic mucosa using a Ussing-type chamber. Various inhibitors were used to investigate the mechanism of action of AEA. The structural change in the membrane and the cytotoxicity of AEA in the intestinal mucosa were evaluated by measuring the electrical resistance of the membrane (Rm) and lactate dehydrogenase (LDH) activity, respectively. AEA significantly increased the permeation of CF in a dose-dependent manner. The enhanced permeability was significantly suppressed by a histamine H1 receptor antagonist, pyrilamine, and a mast cell stabilizer, ketotifen, but not by a histamine H2 receptor antagonist, cimetidine. The enhancing effect was also inhibited by an inhibitor of protein kinase C (PKC). Potential difference and short-circuit current values decreased, while Rm values remained constant throughout the experiment. The addition of AEA to the mucosal solution decreased Rm to 30%, but then remained constant. LDH activity with AEA was not significantly different from that of the control. In conclusion, AEA is a candidate for effective absorption enhancers without damage of the membrane and cytotoxicity. We propose that AEA stimulates mast cells within the colonic mucosa to release histamine, which probably bind to the H1 receptor. The intracellular PKC route activated by H1 receptor activation enhances the permeability of water-soluble and poorly permeable drugs via opening of tight junctions in rat colonic membrane.
