Species differences in the choleretic response to bile salts

Area of Science:

• Hepatology and Gastroenterology
• Pharmacology and Toxicology
• Comparative Physiology

Background:

• Bile acids are crucial for digestion and enterohepatic circulation.
• Species-specific differences in bile acid metabolism and transport are known.
• The choleretic effect of bile acids can vary significantly between animal models.

Purpose of the Study:

• To investigate and compare the choleretic effects of cholic acid, taurocholic acid, and dehydrocholic acid in rats, rabbits, and dogs.
• To explore the influence of basal bile flow rates on the choleretic response across species.
• To examine species-specific differences in bile acid conjugation and biliary excretion.

Main Methods:

• Intravenous administration of cholic acid, taurocholic acid, and dehydrocholic acid at varying doses (3.12-100 mg/kg) to rats, rabbits, and dogs.
• Measurement of bile flow rates and duration of choleretic response.
• Analysis of biliary bile acid concentrations and assessment of bile acid conjugation rates.

Main Results:

• Dogs exhibited a significantly greater choleretic response to cholic acid (sixfold increase) compared to rats and rabbits (2-2.5-fold increase), with a longer duration.
• Species differences in choleretic response were also observed for taurocholic and dehydrocholic acids, with varying return rates to baseline bile flow.
• Basal bile flow rates were considerably higher in rats and rabbits than in dogs, suggesting a role in modulating the choleretic effect.

Conclusions:

• Significant interspecies variations exist in the choleretic efficacy and duration of action of administered bile acids.
• Differences in basal bile production rates contribute to the observed species-specific choleretic responses.
• The mechanism by which bile acids increase bile flow may be complex, as evidenced by inconsistent effects of taurocholic acid on rat bile flow despite increased biliary bile acid concentration.