View the slide viewer

Have questions about this assay kit?

Human CAR-2 Reporter Assay Kit

1 x-96 well format assays
3 x-32 assays in-96 well format
1 x-384 well format assays
1 x-96 well format assays
3 x-32 assays in-96 well format
1 x-384 well format assays

Product Description and Product Data

This is an all-inclusive cell-based luciferase reporter assay kit targeting the Human Constitutive Androstane Receptor-2 (CAR-2). INDIGO’s CAR-2 reporter assay utilizes proprietary mammalian cells that have been engineered to provide constitutive expression of the CAR-2. In addition to CAR-2 Reporter Cells, this kit provides two optimized media for use during cell culture and in diluting the user’s test samples, a reference agonist, Luciferase Detection Reagent, and a cell culture-ready assay plate. The principal application of this assay is in the screening of test samples to quantify any functional activity, either agonist or antagonist, that they may exert against human CAR-2. This kit provides researchers with clear, reproducible results, exceptional cell viability post-thaw, and consistent results lot to lot. Kits must be stored at -80C. Do not store in liquid nitrogen. Note: reporter cells cannot be refrozen or maintained in extended culture.


  • Clear, Reproducible Results

  • All-Inclusive Assay Systems
  • Exceptional Cell Viability Post-Thaw
  • Consistent Results Lot to Lot

Product Specifications

Target TypeNuclear Hormone Receptor
Receptor FormHybrid
Assay ModeAgonist, Antagonist
Kit Components
  • CAR-2 Reporter Cells
  • Cell Recovery Medium (CRM)
  • Compound Screening Medium (CSM)
  • DEHP (ref. agonist; in DMSO))
  • Detection Substrate
  • Detection Buffer
  • White, sterile, cell-culture ready assay plate
Shelf Life6 months
Orthologs AvailableNo
Shipping RequirementsDry Ice
Storage temperature-80C


Agonist dose-response analyses of Human CAR2. Performance of the human CAR2 assay using the reference agonists DEHP (bis 2- ethylhexyl phthalate; provided). Luminescence was quantified using a TECAN Spark plate-reading luminometer. Average relative light units (RLU) and corresponding standard deviation (SD) values were determined for each treatment concentration (n ≥ 6). Fold-activation and Z’ values were calculated as described by Zhang, et al. (1999). Non-linear regression and EC50 analyses were performed using GraphPad Prism software. The high Z' score confirms the robust performance of this assay, and its suitability for HTS.

Target Background

The constitutive androstane receptor (CAR), also known as NR1I3 (nuclear receptor subfamily 1, group I, member 3), is a nuclear hormone receptor with activity similar to that seen in other steroid receptors such as estrogen or progesterone but more similar in form to PPAR, LXR and RXR. CAR functions differently from other steroid receptors and its activity is still being elucidated. It is known to act in concert with PXR to detoxify xenobiotics. CAR is encoded by the NR1I3 gene. This gene encodes a member of the nuclear receptor superfamily, and is a key regulator of xenobiotic and endobiotic metabolism. The protein binds to DNA as a monomer or a heterodimer with the retinoid X receptor and regulates the transcription of target genes involved in drug metabolism and bilirubin clearance, such as cytochrome P450 family members. Unlike most nuclear receptors, this transcriptional regulator is constitutively active in the absence of ligand but is regulated by both agonists and inverse agonists. Ligand binding results in translocation of this protein to the nucleus, where it activates or represses target gene transcription. These ligands include bilirubin, a variety of foreign compounds, steroid hormones, and prescription drugs. Multiple transcript variants encoding different isoforms have been found for this gene. CAR exists as three predominant splice variants in humans depicted as CAR-1, CAR-2 and CAR-3. Each has unique biological properties. These splice variants do not exist in rat and mouse.

Unlike CAR-1, CAR-2 is not constitutively active, showing ligand-dependent activation of reporter genes linked to genetic response elements derived from CYP2B6 or CYP3A4 promoters. Diethylhexyl phthalate (DEHP) is a strong agonist of CAR-2 but has no activity toward CAR-1 or CAR-3.

It is noteworthy, and a source of experimental confusion, that a number of xenobiotics characterized as activators of human CAR (including phenobarbital) actually modulate the receptor’s activity via indirect mechanisms. In other words, such chemicals do not directly bind to CAR; rather, they impact the activity of upstream regulatory mechanisms that impinge on CAR activity. Hybrid nuclear receptors in which the native N-terminal DNA binding domain (DBD) has been substituted with the GAL4 DBD, such as is used in this reporter assay system, likely will not be responsive to chemical modulators that act through indirect mechanisms.

The principle application of this assay product is in the screening of test samples to quantify functional activities, either agonist or antagonist, that they may exert against the human constitutive androstane receptor.


Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is an organophosphate flame retardant. The primary TDCPP metabolite, bis(1,3-dichloro-2-propyl) phosphate (BDCPP), is detectable in the urine of over 90 % of Americans. Epidemiological studies show sex-specific associations between urinary BDCPP levels and metabolic syndrome, which is an established risk factor for type 2 diabetes, heart disease, and stroke. We used a mouse model to determine whether TDCPP exposure disrupts glucose homeostasis. Six-week old male and female C57BL/6J mice were given ad libitum access to diets containing vehicle (0.1 % DMSO) and TDCPP resulting in the following treatment groups: 0 mg/kg/day, 0.02 mg/kg/day, 1 mg/kg/day, or 100 mg/kg/day. After being on the experimental diet for five weeks without interruption, body composition was analyzed, glucose and insulin tolerance tests were performed, and fasting glucose and insulin levels were quantified. TDCPP at 100 mg/kg/day caused male sex-specific adiposity, fasting hyperglycemia, and insulin resistance. TDCPP-induced modulation of nuclear receptor activation was investigated using an in vitro screen to identify potential mechanisms of metabolic disruption. TDCPP activated farnesoid X receptor (FXR) and pregnane X receptor (PXR), and inhibited the androgen receptor (AR). PXR target genes, but not FXR target genes, were upregulated in livers from mice exposed to 100 mg TDCPP/kg/day. Interestingly, PXR target genes were differentially expressed in livers from both males and females. It remains to be determined whether TDCPP-induced metabolic disruption occurs via modulation of nuclear receptor activity. Taken together, these studies build upon the association of TDCPP exposure and metabolic syndrome in humans by identifying sex-specific effects of TDCPP on glucose homeostasis in mice.

Also available as a service

Constitutive Androstane Receptor-2 (CAR-2, NR1I3i2)

Have questions about this assay kit?