In the present study, we aimed to investigate the underlying mechanism of acetaminophen（APAP）-induced hepatotoxicity by measuring the expression levels of liver transporters and concentrations of bile acids（BAs） in rat plasma and liver. SD rats（42） were randomly assigned into six groups, including 6-h control group, APAP 6-h group, 12-h control group, APAP 12-h group, 24-h control group and APAP 24-h group. The estimation study of BAs in plasma and liver was performed on LC-MS/MS. The levels of bile salt export pump（Bsep）, multidrug resistant protein 2（Mrp2）, multidrug resistant protein 4（Mrp4）, Na＋/taurocholate cotransporting polypeptide（Ntcp） and organic anion transporting polypeptide 2（Oatp2） in the liver were analyzed by Western blotting analysis. Compared with the corresponding control groups, no difference was found in the BA levels and the expressions of BA transporters in the plasma and liver after 6 h of APAP administration. While BA levels were significantly decreased in the plasma and increased in the liver after 12 h of APAP administration（P0.05）; and the expressions of Bsep and Mrp2 were significantly reduced（P0.05）. After 24 h of APAP administration, BA levels were both greatly increased in the plasma and liver（P0.05）; and the expressions of Mrp4 and Oatp2 were significantly decreased（P0.05）. In response to over-dose APAP, Bsep, Mrp2, Mrp4 and Oatp2 levels were reduced at different time points, causing the accumulation of BAs, and such accumulation may ultimately lead to the severe liver injury, which could be an underlying mechanism of the APAP-induced hepatotoxicity.
