Prostaglandin E(2) (PGE(2)) plays an important role in genitourinary function. Multiple enzymes are involved in its biosynthesis. Here we report the genomic structure and tissue-selective expression of cytosolic PGE(2) synthase (cPGES) in genitourinary tissues. Full-length mouse cPGES cDNA was cloned by reverse transcript-polymerase chain reaction (RT-PCR) and 5'- and 3'-rapid amplification of cDNA ends (RACE). Analysis of a cPGES cDNA with partially sequenced cPGES genomic clones and bioinformatic databases demonstrates that the murine cPGES gene spans approximately 22 kb and consists of eight exons. The cPGES gene promoter is GC-rich and contains many SP1 sites but lacks an obvious TATA box motif. RNase protection assay revealed constitutive expression of cPGES was greatest in the testis with lower levels in the ovary, kidney, bladder and uterus. In situ hybridization studies demonstrated that cPGES mRNA was most highly expressed in the epithelial cells of seminiferous tubules in the testis. In the female reproductive tissues, cPGES was mainly localized in ovarian primary and secondary follicles and oviductal epithelial cells with less expression in uterine endometrium. In the kidney cPGES expression was diffusely expressed. In urinary bladder, cPGES expression was restricted to the transitional epithelial cells. This expression pattern is consistent with an important role for cPGES-mediated PGE(2) in urogenital tissue function.