The EP4 receptor is one of four GPCRs that mediate the actions of prostaglandin E2 (PGE2). The diverse effects of PGE2 acting via EP4 receptors point to the need to identify novel agonists and antagonists, both to further elucidate the function of this receptor subtype and for use as therapeutics for various diseases. Cayman's EP4 Receptor (rat) Reporter Assay Kit consists of a 96-well plate coated with a transfection complex containing DNA constructs for rat EP4 receptor and a cAMP response element regulated Secreted Alkaline Phosphatase (SEAP) reporter (EP4 Receptor Reverse Transfection Strip Plate). Cells grown on the transfection complex will express EP4 at the cell surface. Binding of agonists to EP4 initiates a signal transduction cascade resulting in expression of SEAP which is secreted into the cell culture media. Aliquots of media are removed at time intervals, beginning at approximately six hours, and SEAP activity is measured following addition of a luminescence-based alkaline phosphatase substrate provided in the kit. The kit is simple to use and can be easily adapted to high throughput screening for therapeutic compounds regulating the activation of EP4. PGE2 is included in the kit for use as a positive control. The kit provides sufficient reagents to measure SEAP activity at three time points using the black plates included.