INTESTINAL-ABSORPTION OF BILE-ACIDS IN THE RABBIT - DIFFERENT TRANSPORT RATES IN JEJUNUM AND ILEUM

Background and Aims: A direct comparison of jejunal and ileal absorpti on rates of bile acids has not been reported, The aim of this study wa s to compare the relative transport rates of different bile acids in t he jejunum and ileum. Methods: Jejunal and ileal rabbit intestinal seg ments were separately perfused with bile acid solutions, and dose-resp onse curves were obtained for taurocholate, ursodeoxycholate, chenodeo xycholate, deoxycholate, and their glycoconjugates. Membrane fluidity and bile acid transport were assessed in brush border membrane vesicle s. Results: Taurocholate showed active transport in the ileum and no t ransport in the jejunum. Unconjugated bile acids showed passive diffus ion in the two tracts, whereas glycoconjugated bile acids showed both components of transport in the ileum and passive diffusion in the jeju num (lower in the latter). A higher membrane fluidity and lower choles terol-to-phospholipid ratio were found in the jejunum, Ursodeoxycholat e reduced bile acid uptake into membrane vesicles from both ileum and jejunum, Conclusions: Active transport is limited to the ileum, Passiv e diffusion is higher through a less fluid membrane with a higher chol esterol-to-phospholipid ratio in the ileum than in the jejunum. Ursode oxycholate inhibition may be at the level of a facilitated, sodium-ind ependent diffusion in the jejunum.