▁ex cret ion ▁of ▁these ▁subst ances ▁is ▁up reg ulated . ▁ ▁Hence , ▁C AR ▁and ▁P X R ▁play ▁a ▁major ▁role ▁in ▁the ▁det ox ification ▁of ▁foreign ▁subst ances ▁such ▁as ▁dru gs . ▁ ▁And ro sten ol ▁and ▁several ▁is om ers ▁of ▁and ro stan ol , ▁and ro stan es , ▁are ▁end ogen ous ▁ant agon ists ▁of ▁the ▁C AR , ▁and ▁despite ▁acting ▁as ▁ant agon ists , ▁were ▁the ▁basis ▁for ▁the ▁naming ▁of ▁this ▁re ceptor . ▁More ▁recently , ▁de h ydro ep i andro ster one ▁( D HE A ), ▁also ▁an ▁and rost ane , ▁has ▁been ▁found ▁to ▁be ▁an ▁end ogen ous ▁ag on ist ▁of ▁the ▁C AR . ▁ ▁Function ▁▁ ▁C AR ▁is ▁a ▁member ▁of ▁the ▁nuclear ▁re ceptor ▁super family , ▁and ▁is ▁a ▁key ▁reg ulator ▁of ▁x en obi otic ▁and ▁ ▁met abol ism . ▁Un like ▁most ▁nuclear ▁re cept ors , ▁this ▁trans cription al ▁reg ulator ▁is ▁const itut ively ▁active ▁in ▁the ▁absence ▁of ▁lig and ▁and ▁is ▁reg ulated ▁by ▁both ▁ag on ists ▁and ▁inverse ▁ag on ists . ▁Lig and ▁binding ▁results ▁in ▁trans location ▁of ▁C AR ▁from ▁the ▁c yt os ol ▁into ▁the ▁nucle us , ▁where ▁the ▁protein ▁can ▁bind ▁to ▁specific ▁DNA ▁sites , ▁called ▁response ▁elements . ▁Binding ▁occurs ▁both ▁as ▁a ▁mon omer ▁and ▁together ▁with ▁the ▁ret ino id ▁X