The constitutive androstane receptor (CAR) was identified as a member of the orphan nuclear hormone receptor family in 1994. Although constitutively active, it can be further activated by `phenobarbitol-like` compounds, the most potent being the synthetic compound TCPOBOP. Upon activation, CAR regulates the xenobiotic drug metabolizing enzymes, cytochrome P450s. There are several overlapping functions between the nuclear receptors PXR and CAR. Recently, CAR, as well as PXR, have been shown to place a role in bile acid clearance and cholestatic liver injury.
