Characterizing drug-metabolizing enzymes and transporters that are CAR-target genes in mouse intestine.

Intestine is responsible for the biotransformation of many orally-exposed chemicals. The constitutive androstane receptor (CAR/Nr1i3) is known to up-regulate many genes encoding drug-metabolizing enzymes and transporters (drug-processing genes/DPGs) in liver, but less is known regarding its effect in intestine. Sixty-day-old wild-type and mice were administered the CAR-ligand TCPOBOP or vehicle once daily for 4 days. In wild-type mice, mRNA was down-regulated by TCPOBOP in liver and duodenum. mice had altered basal intestinal expression of many DPGs in a section-specific manner. Consistent with the liver data (Aleksunes and Klaassen, 2012), TCPOBOP up-regulated many DPGs (, and ) in specific sections of small intestine in a CAR-dependent manner. However, the mRNAs of and were previously known to be up-regulated by TCPOBOP in liver but were not altered in intestine. Interestingly, many known CAR-target genes were highest expressed in colon where CAR is minimally expressed, suggesting that additional regulators are involved in regulating their expression. In conclusion, CAR regulates the basal expression of many DPGs in intestine, and although many hepatic CAR-targeted DPGs were CAR-targets in intestine, pharmacological activation of CAR in liver and intestine are not identical.