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The long term administration of chenodeoxycholic acid in man has to be regarded with caution because chenodeoxycholic acid has caused liver damage in various species of animals, including primates. To study the effect of three doses of chenodeoxycholic acid (10, 40, and 100 mg per kg per day) on hepatic function and morphology, biliary bile acid composition and the reversibility of changes were investigated in 22 rhesus monkeys. After 6 months of treatment with 40 and 100 mg per kg per day, bile duct proliferation, portal tract inflammation and fibrosis, bile canalicular bleb formation, and hypertrophy of the smooth endoplasmic reticulum were associated with elevated serum levels of oxaloacetic transaminase, glutamic pyruvic transaminase, and leucine aminopeptidase. In the bile, the proportion of chenodeoxycholic acid and its bacterial metabolite, lithocholic acid, rose to approximately 85 and 10% of the total bile acids. After chenodeoxycholic acid was withdrawn for 3 months, the hepatic morphological lesions persisted in some animals although biliary bile acid composition returned to normal. No hepatic abnormalities were seen in the animals treated with 10 mg per kg per day. The findings suggest that long term treatment of rhesus monkeys with high doses of chenodeoxycholic acid results in severe hepatic histological lesions that can persist after discontinuation of the bile acid.

Chenodeoxycholic acid is an important drug for the treatment of cholesterol cholelithiasis in man. Although no toxicity has been demostrated in man, liver lesions develop in rhesus monkeys treated with chenodeoxycholic acid. To elucidate the mechanism of toxicity, chenodeoxycholic acid. To elucidate the mechanism of toxicity, chenodeoxycholic acid was fed daily to three groups of 6 animals each at the following dose: 10, 40, and 100 mg per kg; 2 separate animals were not treated and served as controls. After 1 month, the animals were killed. During the treatment period, most blood tests (e.g., blood count, blood urea nitrogen, albumin, SGOT, lactate dehydrogenase) remained within normal limits, but there was a significant dose-related increase in serum leucine aminopeptidase levels. The percentage of lithochlic acid, the 7-dehydroxylated bacterial metabolite of chenodeoxycholic acid, rose from 1% in the control animal to almost 14% in the 100 mg per kg-treated group. Liver biopsies obtained before treatment and at necropsy showed no significant changes. Thus, exposure of the liver to increased amounts of lithocholic acid during chenodeoxycholic acid treatment might result in elevation of serum leucine aminopeptidase activity.