Bile acid synthesis in young and old rats

Bile acid synthesis from orally administered C-14-cholesterol or from C-14-mevalonic acid administered intravenously were examined in male and female 2-, 12- and 24-month-old rats. About 5-9% of the C-14-cholesterol administered was recovered as bile acids from the small intestine 3 days after administration. The value in the case of C-14-mevalonic acid was about 1/10 that of C-14-cholesterol. Major bile acids were cholic acid and beta-muricholic acid and the formation ratio of cholic acid increased in aged rats, although no further difference was found between 12- and 24-month-old animals of either sex. Male rats formed more beta-muricholic acid than females at all ages examined. In addition, no significant difference was found in the bile acid composition between both precursors, C-14-cholesterol and C-14-mevalonic acid.