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Browsing by Subject "efflux-kuljetus"

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  • Järvinen, Erkka (2016)
    UDP-glucuronosyltransferases (UGTs) catalyse glucuronidation reactions between glucuronic acid and drug molecules, which contain nucleophilic groups, mostly hydroxyls, amines or carboxylic acids. Glucuronidation is the most important reaction in the conjugative drug metabolism. Because these conjugates are not usually able to cross cell membranes passively, they need active efflux transport. Efflux transporters mostly belong to superfamily of ATP-binding cassette transporters (ABC). Subfamily C of ABC transporters (ABCC) are known to be involved in efflux transport of glucuronides. Especially MRP2 (ABCC2) and MRP3 (ABCC3) play key roles in the elimination of glucuronide conjugates of drugs. MRP2 is localized in the apical membranes of hepatocytes and enterocytes, whereas MRP3 is localized in the basolateral membranes of the respective cells. On the other hand, UGT1A1 and UGT2B7 are highly expressed in liver and small intestine and are the most important UGTs in drug metabolism. It is known, that UGTs and efflux transporters work together forming interplay to eliminate drugs. Therefore, studying both of them in the same in vitro system is in important focus of drug metabolism studies. The Madin Darby canine kidney cell line (MDCK) is one of the standard in vitro tools in drug metabolism studies. In this study, MDCK was chosen for a cell line to co-express UGTs (UGT1A1 or UGT2B7) and efflux transporters (MRP2 and MRP3 simultaneously. Therefore, cloning of the UGT2B7 cDNA and the ABCC3 cDNA encoding MRP3 was aimed in this study. On the other hand, the UGT1A1 cDNA was already cloned in-house and MRP2 expressing MDCK cells were established earlier. Cloning of the UGT2B7 cDNA was not successful in this study despite of several different strategies such as PCR-amplification of the cDNA fragment using kidney or liver sscDNA as template. Cloning of the ABCC3 cDNA encoding MRP3 was achieved and a mammalian expression vector containing this cDNA was constructed. In addition, the mammalian expression vector containing the UGT1A1 cDNA was used to establish MDCK-UGT1A1 cells and this cell line was characterized regarding the expression of UGT1A1 mRNA and UGT1A1 protein amount. Furthermore, establishment of MDCK-UGT1A1-MRP2 cell line was attempted in this study without success. The mammalian expression vector containing the ABCC3 cDNA encoding MRP3 could be used for future experiments to achieve novel cell lines such as MDCK-UGT1A1-MRP3 and MDCK-UGT1A1-MRP2-MRP3 for drug metabolism studies. In addition, the novel cell line MDCK-UGT1A1 could be used for drug metabolism studies in further experiments, but also as a cell line for further establishment of above cell lines. On the other hand, the cloning of the UGT2B7 cDNA needs optimization and several different strategies should be used to achieve the mammalian expression vector containing this cDNA.