Composition of gallbladder bile in male wild-type and Cyp8b1^–/– mice. Amounts of individual bile acids in the gallbladder bile of wild-type and Cyp8b1^–/– mice were determined by gas chromatography/mass spectrometry and are indicated as a percentage of the entire pool. The position and stereochemistry of hydroxyl groups on the ring structures of each bile acid are indicated in parentheses. Similar results were obtained when the total bile acid pool was analyzed by HPLC.