Effects of Acute Bile Acid Administration on Biliary Lipid Secretion in Healthy Volunteers

We investigated the effects of acute bile acid administration on biliary lipid secretion in 8 healthy subjects by a perfusion technique that employed an orojejunal tube with an occlusive balloon. In seventeen 8-h experiments, we measured bile acid, cholesterol, and phospholipid outputs before, during, and after rapid replacement of the bile acid pool with chenodeoxycholic, ursodeoxycholic, or cholic acid. Cholesterol and phospholipid outputs were linearly coupled to bile acid output before and after endogenous bile acid pool replacement. Cholesterol secretion was significantly lower after replacement with ursodeoxycholic acid than during the prereplacement phase or after replacement with chenodeoxycholic or cholic acid. Replacement with chenode oxycholic acid had no significant effect on cholesterol or phospholipid secretion, whereas replacement with either ursodeoxycholic or cholic acids significantly reduced phospholipid output. We conclude that in healthy volunteers, acute administration of different bile acids specifically alters biliary lipid secretion. The rapidity of the changes in cholesterol and phospholipid secretion suggests that these effects are secondary to alterations in the secretory coupling of biliary lipids rather than to changes in their synthesis or absorption.