Comparison of the effects between ursodeoxycholic and chenodeoxycholic acids on liver function and structure and bile acid composition in the Rhesus Monkey.

The hepatotoxic potential of the cholelitholytic bile acids, chenodeoxycholic (chenic), and ursodeoxycholic acids, was compared in the rhesus monkey. A placebo-controlled treatment trial with 40 and 120 mg/kg/day doses of chenic acid and ursodeoxycholic acid, respectively, was conducted in 20 animals. Both chenic and ursodeoxycholic acids induced comparable abnormalities of liver function and structure. Liver biopsies, performed before and after 6 mo of treatment, showed the development of distinct light microscopic changes, including inflammation, fibrosis, and ductular proliferation in the portal fields as well as lobular rearrangement with formation of septa and regenerative nodules. Electron microscopy confirmed light microscopy, but showed no specific changes of cell organelles. Light microscopic examination of the kidneys, lungs, heart, intestine, and brain in 10 monkeys, which were sacrificed after 6 mo of controlled bile acid treatment, showed no abnormalities. Biliary lithocholic acid, all of which was unsulfated, increased several-fold to comparable levels in the bile acid-treated groups. Follow-up studies 6 mo after termination of bile acid treatment showed normalization of liver function tests and of bile acid composition as well as a considerable improvement of the histologic abnormalities. However, the restitution of normal liver structure was incomplete, with fibrosis and mild inflammation persisting in the portal fields. Our studies show that, in this primate species, chenic and ursodeoxycholic acids have comparable hepatotoxic effects, which are associated with similar increases of unsulfated lithocholic acid in bile.