Potential mechanism of cholagogic effect about Gardenia Jasminoides Ellis (Zhizi)-mediated increase of bile acids urinary excretion in normal rats

Objectives Gardenia Jasminoides Ellis (Zhizi), belonging to Rubiaceae family, has been traditionally used for treatment cholestasis and jaundice for centuries in Asian countries. In the theory of Traditional Chinese Medicines, Zhizi could dispel dampness and heat via the urine to execute its choleretic effects. However, the potential molecular mechanism has been still poorly clarified. Here, we investigated the effect of different dose of Zhizi aqueous extract powder (0.3 g/kg/d and 0.9 g/kg/d) on urinary excretion of bile acids (BAs), and defined the potential mechanism via renal BAs efflux transporters Mrp2 and Mrp4 in normal rats. Methods Male Wistar rats were orally administrated with 0.3 or 0.9 g/kg/d dose of Zhizi aqueous extract powder for 2 weeks, then body weight, serum aminotransferase, total BAs concentrations in liver, bile, serum, kidney and urine, 1 h bile flow, 12-h urinary volume, biliary and urinary excretion amount of total BAs as well as protein expression of major renal BAs efflux transporter Mrp2 and Mrp4, were all evaluated. Results Zhizi especially the high dose of Zhizi aqueous extract powder could reduce hepatic total BAs concentration. Additionally, bile flow and biliary excretion had no significant difference, but the remarkable increasing urinary excretion of BAs and 2 to 3 folds up-regulated renal Mrp2 expression were observed after administrated with Zhizi as compared with the control group. Conclusion The findings indicate that Zhizi reduces hepatic total BAs level by increasing urinary excretion rather than the biliary excretion of BAs, which, in turn ascribed to elevated protein expression of Mrp2 at apical membrane of renal tubular epithelial cells.