Effect of dehydrocholic, chenodeoxycholic, and taurocholic acids on the excretion of bilirubin

The effects of IV bile acid infusion (at approx 20% of normal excretion rate) on the biliary excretion of 3-alpha-hydroxy bile acids and bilirubin were investigated in ponies prepared surgically with chronic external biliary fistulas. Endogenous bile acid excretion (approx 45 mumol/min) decreased to the hepatic synthesis rate (approx 1.5 mumol/min) during the initial 4 to 5 hours of bile drainage. In type 1 studies, both chenodeoxycholic and taurocholic acid infusion (8 to 9 mumol/min) increased bilirubin excretion by 58% to 82% following 5 hours of biliary diversion. During type 2 studies, 3-hour IV infusions (10.5 mumol/mon) of dehydrocholic acid, 4 hours following biliary diversion, increased bile flow by 45% to 62% and excretion of 3-alpha-hydroxy bile acid by 34% to 36% above preinfusion (hepatic synthesis) levels. Bilirubin excretion was not significantly changed during those increases in bile flow and bile acid excretion. Immediately after dehydrocholic acid infusion, taurocholic acid infusion (8.1 mumol/min) greatly increased bilirubin excretion for 1 hour (a reversal of hepatic storage identical to that found during type 1 studies), prolonged excretion (mg/2 hours) being two to three times that caused by dehydrocholic acid infusion. Bilirubin excretion appeared to correlate with the micelle-forming capacity of endogenous bile acids as opposed to the nonmicelle-forming characteristic of synthestic dehydrocholic acid.