RESUMO
OBJECTIVE: To investigate the choleretic effect and molecular mechanisms of action of peppermint oil (PO), the main component of Danshu capsules (Sichuan Jishengtang Pharmaceutical Co., Ltd., Pengzhou, Sichuan Province, China). METHODS: Bile secretion was measured by biliary drainage in rats. Total bile acids, total cholesterol and bilirubin in bile were determined. Cholesterol 7α-hydroxylase (CYP7A1), and farnesoid X receptor (FXR) messenger ribonucleic acid (mRNA) levels were assessed in HepG2 cells (a human hepatocellular carcinoma cell line) by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: PO significantly promoted bile and bile acid secretion in rats. It also increased bile acid efflux and decreased cholesterol levels (P < 0.01) in bile. In HepG2 cells the mRNA levels of CYP7A1 and FXR were significantly upregulated after treatment with PO. CONCLUSIONS: PO stimulates bile fluid secretion and thus has a choleretic effect. PO might play a role in upregulating CYP7A1 and FXR mRNA levels, suggesting that the molecular mechanisms are related to gene expression involved in bile acid synthesis.