Abstract: The study was conducted to investigate the level difference of multidrug resistance protein 2 (MRP2) proteins and mRNA expressions in the liver, duodenum, jejunum, ileum and colon of the healthy and E. coliinfected rats. Twenty healthy adult SD rats were randomly divided into control group (administered with sterile pathogenfree physiology saline) and E. coliinfected group. The immunohistochemical and real time RTPCR methods were used in this study. The results showed that MRP2 was expressed in all tissues of healthy and infected rats. Positive reaction of MRP2 protein was shown in the bile duct cell surface of liver (liver bile capillary membrane) and the mucosa of the intestines layer of healthy and infected rats, while positive reaction in the liver portal vein was weak. For the healthy rats, MRP2 was widely and highly expressed in the cell membrane of liver bile capillary membrane compared with that of the near portal vein. Strong positive reaction was found in the liver bile capillary membrane, portal areas and intestines mucosa layer. Compared with the healthy rats, positive reaction or weak positive reaction was shown in these areas of infected rats, but positive reaction was obviously weaker than those of the healthy rats. MRP2 protein showed strong positive in liver, duodenum and jejunum and positive in ileum and colon of healthy rats. However, MRP2 protein showed positive in duodenum and jejunum and weak positive in liver, ileum and colon in infected rats. The expression level of MRP2 mRNA in liver and small intestines of the E. coliinfected rats was significantly lower (P<0.05) compared to that in healthy rats. All these results indicated that MRP2 transporter in SD rats could be downregulated during the acute phase response to E. coli infection.