Effect of bile acid on hepatic excretion and storage of bilirubin in ponies.

This study examined the impact of bile acid on the process of bilirubin uptake and excretion in horses. The researchers found that normal levels of bilirubin excretion were reliant on bile acid.

Background and Methodology

• The researchers were studying the impact of bile acid on the absorption and excretion of bilirubin in ponies who had chronic biliary T-tube fistulas.
• The ponies’ bile was collected and examined to investigate the bilirubin excretion levels.
• To measure how much bilirubin was being absorbed, a radioactive tracer (14C-labeled bilirubin) was added to the plasma and its decrease was monitored.

Results

• When bile acid excretion was low due to continuous drainage without bile acid replacement, bilirubin excretion was found to be 37% less than its uptake.
• However, when the ponies were infused with taurocholic acid to replace the bile acids, the amount of bilirubin being taken up and excreted was nearly the same.
• Interestingly, after the bile acid reserves were depleted, adding back bile acids with taurocholic acid prompted a major increase in both the concentration and excretion of bilirubin for about an hour. After this initial increase, bilirubin excretion was maintained at a rate approximately 30% greater than the preinfusion rate.

Conclusions

• The study determined that the excretion of bile acid is a necessary process for normal levels of bilirubin excretion.
• Without sufficient levels of bile acid, the excretion of bilirubin is lowered, which suggests that the bile acid is playing a key role in the process.
• Furthermore, quick replacement of bile acids after depletion can result in a temporary surge in bilirubin concentration and excretion, followed by maintained increased levels of excretion.