Sex, Organ, and Breed Differences in the mRNA Expression of Drug Transporters in the Liver and Kidney of Pigs.

Domestic pigs are attractive as an animal model for humans because of their anatomical and physiological similarities to humans. In this study, sex, organ, and breed differences in the mRNA expression of drug transporters such as breast cancer resistance protein (BCRP), multidrug resistance protein 1 (MDR1), multidrug resistance associated protein 2 (MRP2), organic anion porting polypeptide 1B3 (OATP1B3), organic anion transporters (OAT1, OAT2, and OAT3), and organic cation transporters (OCT1 and OCT2) were examined by RT-PCR in the liver and kidney of 5-month-old Meishan and Landrace pigs. No sex differences in the amount of BCRP mRNA were observed in both breeds. In Meishan pigs, sex differences (male < female) in the mRNA amounts of MDR1, OATP1B3, and OCT1 were observed in the liver. Similarly, sex differences in the mRNA amounts of MRP2, OAT1, OAT2, OAT3, and OCT2 were observed in the kidney of Meishan pigs: male > female for MRP2, OAT3, and OCT2, and male < female for OAT1 and OAT2. However, no such sex differences were observed in Landrace pigs. In addition, regardless of breed, hepatic OAT1, OAT3, and OCT2 mRNAs and renal OATP1B3 mRNA were not detected. Thus, organ and breed differences in the expression of drug transporters suggest the existence of genetically controlled organ-selective factors. Furthermore, additional experiments in castrated and/or testosterone propionate-treated pigs strongly suggested that sex and breed differences in the gene expression of drug transporters, especially hepatic OCT1 and renal OAT1, were primarily due to the difference in serum testosterone concentration.