||This assay system utilizes proprietary human cells engineered to provide constitutive, highlevel expression of the Rat Pregnane X Receptor (nr1i2), a ligand-dependent transcription factor commonly referred to as PXR. PXR is also known as the Steroid and Xenobiotic sensing nuclear Receptor (SXR). The reporter Cells express a hybrid form of the rat PXR. The N-terminal sequence encoding the PXR DNA binding domain (DBD) has been substituted with that of the yeast GAL4-DBD. The native PXR ligand binding domain (LBD) and other C-terminal domains remain intact and functional. Ligand interaction activates the receptor, causing it to binds to the GAL4 DNA binding sequence, which is functionally linked to a resident luciferase reporter gene. Thus, quantifying changes in luciferase activity in the treated reporter cells provides a sensitive surrogate measure of the changes in PXR activity. The principle application of this reporter assay system is in the screening of test samples to quantify any functional activity, either agonist or antagonist, that they may exert against rat PXR. PXR Reporter Cells are prepared using the proprietary CryoMite process. This cryo-preservation method yields exceptional cell viability post-thaw, and provides the convenience of immediately dispensing healthy, division-competent reporter cells into assay plates. There is no need for cumbersome intermediate treatment steps such as spinand-rinse of cells, viability determinations, or cell titer adjustments prior to assay setup.The Nuclear Receptor Reporter Assays are all-inclusive cell-based assay systems. In addition to PXR Reporter Cells, this kit provides two optimized media for use during cell culture and in diluting the users test samples, a reference agonist, Luciferase Detection Reagent, and a cell culture-ready assay plate.