Vinegar-baked Radix Bupleuri modulates the cell membrane constituents and inhibits the P-gp activity in rat hepatocytes

BACKGROUND Vinegar-baked Radix Bupleuri (VBRB) enhances the effects of other drugs on the liver by increasing drug distribution to the liver, but the mechanism of action remains unclear. The present study was designed to determine the effects of VBRB on the membrane permeability, constituents, and P-glycoprotein (P-gp) activity of hepatocyte BRL cells, in order to interpret the liver targeting enhancing effects of VBRB. METHODS The membrane permeability and P-gp expression were analyzed by flow cytometry. The membrane constituents were determined by an automatic biochemistry analyzer and thin-layer chromatography. RESULTS The results showed that, compared with the control, VBRB enhanced the membrane permeability by 41-67% (P < 0.05), which occurred in the absence of any cytotoxicity. VBRB had marginal effects on the cholesterol content, but significantly affected the total protein contents and the lipid constituents of the cell membrane in a dose- and time-dependent manner. VBRB inhibited P-gp expression in the cell membrane by 59-86% (P < 0.01). CONCLUSION VBRB affects the constituents of BRL cells and increases its permeability, which may help explain its liver-targeting effects.