Bile acid synthesis in young and old rats

Bile acid synthesis from orally administered 14C-cholesterol or from 14C-mevalonic acid administered intravenously were examined in male and female 2−, 12− and 24-month-old rats. About 5–9% of the `4C-cholesterol administered was recovered as bile acids from the small intestine 3 days after administration. The value in the case of 14C-mevalonic acid was about 110 that of 14C-cholesterol. Major bile acids were cholic acid and β-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 β-muricholic acid than females at all ages examined. In addition, no significant difference was found in the bile acid composition between both precursors, 14C-cholesterol and 14C-mevalonic acid.