| Recently, people pay more attention to the drug bioavailability with the development of scale culture. It is reported that the study of drug transporter protein in vivo has become the most popular field in the world. Several members of the ATP-binding cassette (ABC) drug efflux transporter family such as MDR1, MRP2, BCRP, which transports the materials in and out of cells, affect the pharmacokinetics of drugs in vivo. In order to find a good way to enhance the bioavailability of drugs, the study was focused on the difference of the expression of MDR1, MRP2and BCRP in liver and intestine of healthy, E.coli-infected and enrofloxacin-treated rats. The study consisted of two parts as below.1. Immunohistochemical study of MDR1, MRP2and BCRP in liver and intestines of healthy and E. coli-infected ratsTo investigate the expressions of ABC transporter proteins (MDR1, MRP2and BCRP) in the liver, duodenum, jejunum, ileum and colon of healthy and E.coli-infected rats, the immunohistochemical method was used. The samples of liver and intestinal(from the jejunum to colon) from healthy and infected rats were collected and studied. Immunohistochemical labelling of ABC transporter proteins was performed using an anti-rat MDR1, MRP2and BCRP antibody. Density of ABC transporter proteins was calculated using image analysis software. The results showed that MDR1, MRP2and BCRP were expressed in all tissues both in healthy and infected rats. Positive reaction were showed in the bile duct cell surface of liver (liver bile capillary membrane) and the mucosa of the intestines layer of both healthy and infected rats, while positive reaction in the liver portal vein were weak. For the healthy rats, MDR1, MRP2and BCRP were widely high 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 were showed in these areas of infected rats, but positive reaction were obviously weak than those of the healthy rats. MDR1protein showed strong positive in liver, duodenum, jejunum and ileum and positive in colon of healthy rats, while MDR1protein showed positive in liver, duodenum, jejunum and ileum and weak positive in colon in infected rats. MRP2protein showed strong positive in liver, duodenum and jejunum and positive in ileum and colon of healthy rats, however MRP2protein showed positive in duodenum and jejunum and weak positive in liver, ileum and colon in infected rats. BCRP protein showed strong positive in duodenum and jejunum and positive in liver, ileum and colon of healthy rats, but in infected rats, BCRP protein showed positive in duodenum and jejunum and weak positive in liver, ileum and colon. All results indicated that some ABC transporters could be down-regulated during the acute phase response to E. coli infection.2. MDRx, MRP2and BCRP mRNA expression in healthy, E. Coli-infected and enrofloxacin-treated ratsTo investigate the level of expressions of MDR1, MRP2and BCRP mRNA in liver, duodenum, jejunum, ileum and colon of both the E. coll-infected and healthy rats, fourty two healthy adult SD rats were randomly divided into control group (administered with sterile pathogen-free physiology saline), E. coli-infected group and experiment group (administered enrofloxacin at dose of2.5mg/Kg and5.0mg/Kg in healthy and infected rats, respectively). All rats of control group as well as experiment groups were killed after they were oral administered continuously for5days, and the liver, duodenum, jejunum, jejunum and colon of rats were immediately collected. The mRNA expression of drug transporter (MDR1、MRP2、BCRP) in above tissues were analyzed by real time RT-PCR. The results showed that expression of MDR1in liver were rapidly decreased in the E. Coli-infected rats. The expressions of MDR1mRNA in duodenum and MRP2mRNA in liver of the E. Coli-infected rats were significiantly lower compared to healthy rats. The MDR1mRNA expressions in liver of the E. Coli-infected rats with administration of enrofloxacin at dose of2.5mg/kg were significantly increased. Compared with the control group, the expressions of MRP2mRNA in liver of the E. coli-infected rats were significantly induced. The MRP2mRNA expressions in duodenum of E. coli-infected rats with enrofloxacin treated at dose of2.5mg/kg were significantly increased. The BCRP mRNA expressions were significantly increased in duodenum of healthy rats with enrofloxacin administration at dose of2.5mg/kg. The study suggested that the treatment of colibacillosis with fluoroquinolones, which resulted in a significant clinical improvement of the animals, also restored the expression of some drug transporters. |
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