Constitutive expression of CYP3A mRNA in Bama miniature pig tissues

The pig, particularly the miniature pig (minipig), is becoming an important animal model due to its physiological and anatomical similarities to humans. Bama minipigs (Sus scrofa domestica), a Chinese natural minipig breed, are a promising animal model. The pig is a useful model for drug metabolism and pharmacological studies due to the similar properties of cytochrome P450 (CYP)3A between pigs and humans. However, a detailed investigation regarding the abundance and expression of CYP3A in porcine tissues, particularly in minipig tissues, has not been performed. The present study investigated constitutive expression of CYP3A mRNA in Bama minipig tissues using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). We found that the expression of CYP3A mRNAs relative to the endogenous control, β-actin (ACTB), was lower than when compared to the expression of the endogenous control, TATA-binding protein (TBP), except for the expression of CYP3A29 mRNA in the spleen, adrenal gland, testis, and epididymis, and CYP3A46 in the spleen. Expression levels of all three CYP3As were highest in the liver amongst all the tissues tested, and the order of relative mRNA expression level of the three CYP3As was different between other tissues. We also analyzed the relative expression of the three CYP3A mRNAs in each tissue. CYP3A46 had the highest expression in all extrahepatic tissues, whereas CYP3A22 had the highest expression in the liver, and CYP3A29 had the lowest expression in all tissues except in the duodenum, where it had higher expression than CYP3A22. Because CYP3A22 and CYP3A46 were the most highly expressed isoforms, it could follow that they are probably important functional CYP3A genes for Bama miniature pig. Our present work will broaden the understanding of the physiological functions of CYP3As in the Bama minipig and promote its application in drug metabolism and pharmacological studies. Our results also indicate that the breed, age, and castration status of the pig should be considered when using the pig as an animal model in pharmacological applications.