Abstract
The effects of two kinds of cyclodextrins (CyDs), α- and β-CyD, on biological membranes were investigated by measuring changes in the absorption of a non-absorbable drug, sulfanilic acid (SA), from the rat small intestine, using in situ and in vitro experiments. After pretreatment with a mucolytic agent, N-acetyl-L-cysteine (N-Ac), only β-CyD increased the absorption of SA significantly compared to the absorption without pretreatment.The mechanism of the enhancing effect of CyDs on the absorption of SA was discussed. Almost no morphological change in the small intestine was observed by pretreatment with N-Ac alone, N-Ac or α- or β-CyD combinations. The liberation of membrane components differed among the CyDs, e.g., α-CyD selectively released phospholipid while β-CyD released mainly cholesterol from the intestinal membrane. It is suggested that the interaction of membrane components with DyDs may be at least partly responsible for the enhanced absorption of SA. Moreover it was found from in vitro electrophysiological experiment, that the alteration in enhanced permeability caused by β-CyD occurred primarily in the transcellular pathways, rather than in the paracellular pathways of the small intestine.These results suggest that the enhancement of intestinal absorption by β-CyD, after removal of the mucin layer from the intestinal surface, is due to the interaction between the membrane components and CyD. This interaction would induce disorder in cell membrane lipid, resulting in the increased permeability of the transcellular route.
