Increased biliary calcium in cholesterol and pigment gallstone disease: the role of altered bile acid composition.

The present study was undertaken to define the relationship between calcium metabolism and bile acid composition in animal models of diet induced cholesterol and pigment gallstones. Groups of prairie dogs were fed either a control non-lithogenic chow (N = 12), a 1.2% cholesterol enriched chow (N = 6, XOL) for two weeks, or a high carbohydrate diet deficient in iron (N = 6, CHO-FeD), or a high carbohydrate diet with normal iron levels (N = 6, CHO) for eight weeks. Hepatic (HB) and gallbladder (GB) bile samples were analyzed for total calcium, cholesterol, phospholipids, total bile acids (TBA), and individual bile acid composition. In each of the four groups, TBA concentrations were essentially similar and taurine conjugates accounted for approximately 90% of TBA in HB bile and about 98% in GB bile. In the control group, cholic acid (CA) was the predominant bile acid and comprised 76% of TBA and chenodeoxycholic (CDCA) accounted for about 13% of the total. Feeding a diet rich in cholesterol caused a significant change in the relative concentrations of individual bile acids of hepatic bile--such that CA decreased significantly (p less than 0.001) while CDCA increased by 300% (p less than 0.001). The changes in secondary bile acids were insignificant. An identical shift in individual bile acid composition was noted in animals maintained on high carbohydrate diet, irrespective of iron content. Similar changes were observed in the GB in the experimental groups.(ABSTRACT TRUNCATED AT 250 WORDS)