Rapid feedback inhibition of endogenous cholic and chenodeoxycholic acid synthesis by exogenous chenodeoxycholic acid in man

Chenodeoxycholic acid (300 mg + 14C) was administered orally to a bile fistula patient receiving a constant infusion of { 3H}mevalonic acid. Suppression of endogenous cholic and chenodeoxycholic acid synthesis occurred within 2 to 4 hours and continued for the next 10 hours; synthesis returned to the baseline level after 18 hours. Incorporation of { 3H}mevalonic acid into both bile acids was also greatly reduced during the first several hours after chenodeoxycholic acid, but almost recovered by 5 hours. The data suggest that multiple feedback sites are involved in the regulation of bile acid synthesis in man.