Effect of capsaicin on bile secretion in the rat

Capsaicin is a popular food ingredient. This study aimed to determine if capsaicin can affect bile flow and bile protein secretion, and the extent to which capsaicin can reach bile in the rat. The effect of capsaicin was studied in anesthetized rats equipped with cannulas inserted into the common bile duct. Capsaicin was administered by intragastric, intraduodenal (4-400 microg/ml; 10-1,000 microg/kg), intravenous (10 microg/kg) routes or applied on the serosal surface of the duodenum at 4 microg/ml. The administration of capsaicin decreased bile flow in comparison to the corresponding basal values, the maximum effect being reached at a concentration of 400 microg/ml of intragastric capsaicin (30.2%; p < 0.01), and 40 microg/ml (30.8%; p < 0.01) of intraduodenal capsaicin, 75 min after drug administration. Meanwhile, a decrease of 24.7 and 40% was observed 60 min after serosal and intravenous capsaicin administration, respectively. Biliary protein secretion was also reduced following capsaicin administration. High-performance liquid chromatography (HPLC) analysis showed that capsaicin was readily excreted into bile, peak levels were reached 75 or 60 min following its intragastric or intraduodenal administration, respectively (range 100-248 and 144-698.6 ng/ml after intragastric or intraduodenal capsaicin at 4-400 microg/ml, respectively). Capsaicin concentrations of 86 and 75 ng/ml could be detected in bile 15 min after intravenous administration or serosal application of the agent, respectively. Results suggest that capsaicin is readily absorbed after its intragastric or intraduodenal administration and goes through hepatobiliary excretion. Results also indicate that administration of capsaicin reduces bile flow and biliary proteins in the rat.