Differing effect of chenodeoxycholic acid and ursodeoxycholic acid on bile acids in rat colonic wall and contents.

Bile acids may promote experimental colonic cancer. Many studies correlate fecal bile acids and colorectal carcinomas. Little is known on bile acids in the colonic mucosa and their relation to luminal bile acids. We, therefore, studied bile acids in colonic wall and contents of normal female Wistar rats and after 14 days' administration of chenodeoxycholic acid or ursodeoxycholic acid (90 mg/kg daily), two bile acids used in medicamentous cholelitholysis. Both regimens increase total bile acids in colonic contents, ursodeoxycholic acid produces a higher rise in toxic lithocholic acid. In the colonic wall, only ursodeoxycholic acid causes an increase of most nonsulfated bile acids including lithocholic acid. Bile acid patterns do not correlate in colonic wall and contents. We conclude that increased colonic wall bile acids after ursodeoxycholic acid administration warrant control in man. In future colorectal carcinoma studies, not only fecal, but also mucosal bile acid concentrations should be correlated to carcinogenesis.