Absorption of unconjugated bile acids and tauroursodeoxycholate in the rat intestine

The absorption of ursodeoxycholate and its tauro-conjugate by the jejunum and the terminal ileum of rat intestine was compared with that of other unconjugated bile acids and taurocholate. In the ligated jejunum, the efficacy of absorption of unconjugated bile acids was in the following order: ursodeoxycholate = deoxycholate > chenodeoxycholate = cholate > lithocholate. This order cannot be explained by the theory that the passive diffusion of bile acids is faster the less hydroxyl bonds in the molecule. These findings on the unconjugated bile acids in the ligated jejunum were further confirmed by perfusion experiments. In the ligated terminal ileum, ursodeoxycholate, cholate and deoxycholate were absorbed as fast as taurocholate or tauroursodeoxycholate, whereas absorption of chenodeoxycholate was significantly slower. The Na⁺-dependency of the absorption of ursodeoxycholate and cholate in the terminal ileum was confirmed by perfusion studies. In conclusion, intestinal absorption of ursodeoxycholate was efficient in both the jejunum and ileum and these results may contribute to the high availability of ursodeoxycholate in various hepatobiliary diseases.