Regulation of mRNA expression of xenobiotic transporters by the pregnane x receptor in mouse liver, kidney, and intestine.

Multiple transporter systems are involved in the disposition of xenobiotics and endogenous compounds. The pregnane X receptor (PXR) is a major chemical sensor known to activate the expression of CYP3A/Cyp3a in humans and rodents. The purpose of this study is to systematically determine whether the major xenobiotic transporters in liver, kidney, duodenum, jejunum, and ileum are induced by pregnenolone-16alpha-carbonitrile (PCN), and whether this increase is mediated by the nuclear receptor PXR. In liver, PCN induced the expression of Oatp1a4 and Mrp3 mRNA in wild-type (WT) mouse liver, but not in PXR-null mice. In kidney, PCN did not alter the expression of any drug transporter. In duodenum, PCN increased Abca1 and Mdr1a mRNA expression in WT mice, but not in PXR-null mice. In jejunum and ileum, PCN increased Mdr1a and Mrp2 mRNA, but decreased Cnt2 mRNA in WT mice, but none of these transporters was altered when PCN was administered to PXR-null mice. Therefore, PCN regulates the expression of some transporters, namely, Oatp1a4 and Mrp3 in liver, as well as Abca1, Cnt2, Mdr1a, and Mrp2 in small intestine via a PXR-mediated mechanism.