Compared effects of synthetic and natural bile acid surfactants on xenobiotic absorption. III. studies with mixed micelles

Abstract

The present work deals with the effects of bile salts on absorption. It has previously been demonstrated that although they are surfactants, these salts are not able to disrupt the aqueous diffusion layer which effectively limits the absorption of the lipophilic compounds. They exhibit less ability less ability to solubilize in their micelles when they are perfused only in the presence of the tested compounds. The present study was carried out with two types of bile salts -sodium taurocholate and sodium glycocholate - along with other compounds naturally occurring in vivo, such as lecithin and sodium oleate. In this way the hypothesis that an intrinsic mechanism is involved in promoting the effect of bile salts on absorption was assessed by stimulating a physiological environment, which always shows mixed micelles of bile salts with phospholipids and fat. Correlations between absorption and lipophilicity parameters are useful for indirect quantification of this phenomenon. The enhancer effect of bile salts on the absorption of lipophilic compounds may be due to their effective absorption in the gut, which helps the disintegration of the micelles. Despite the fact that the characteristics of natural surfactants are not as good as those of synthetic surfactants for promoting absorption, a consideration of all their properties can explain all the features reported.