Effect of cecum and appendix on 7 alpha-dehydroxylation and 7 beta-epimerization of chenodeoxycholic acid in the rabbit.

The effect of surgical removal of cecum and appendix on bile acid metabolism was studied in the rabbit. Bile acid composition of bile and intestinal contents were analyzed by gas-liquid chromatography and individual bile acids were further identified by mass spectrometry. In normal, intact rabbits (group I), the biliary bile acids consisted largely of deoxycholic acid (DA) 95.3 +/- 1.0 (mean +/- SE) %; cholic acid (CA) 2.3 +/- 1.1% and lithocholic acid (LA) 1.0 +/- 0.3% were also detected. Removal of cecum and appendix (group II) produced significant changes in biliary bile acid composition: DA fell to 58.3 +/- 31.8%, CA rose to 37.7 +/- 10.4%, and LA was barely detectable (0.3 +/- 0.1%). Administration of chenodeoxycholic acid (CDA), 125 mg/day, produced severe hepatotoxicity, reduced food intake, and produced weight loss (group III). Biliary LA rose to 15.0 +/- 1.3%, while DA was 61.3 +/- 14.0% and CDA 21.8 +/- 14.6% of total biliary bile acids. Feeding CDA to animals without cecum and appendix (group IV) resulted in a slight increase of LA (3.2 +/- 2.2%) compared to group III, and appreciable amounts of ursodeoxycholic acid (UDA) 32.0 +/- 9.8% and of 7-ketolithocholic acid (7-KLA) 3.0 +/- 0.6% appeared in bile. The animals of group IV exhibited no hepatotoxicity and ate and gained weight normally. These results indicate that the microbial population of cecum and appendix is active in 7alpha-dehydroxylation of primary bile acids and that removal of these organs results in an increased formation of UDA by an unknown mechanism.-Yahiro, K., T. Setoguchi, and T. Katsuki. Effect of cecum and appendix on 7alpha-dehydroxylation and 7beta-epimerization of chenodeoxycholic acid in the rabbit.