Comprehensive Analysis of Prostaglandin Metabolic Enzyme Expression During Pregnancy and the Characterization of AKR1B1 as a Prostaglandin F Synthase at the Maternal-Conceptus Interface in Pigs

Prostaglandins (PGs) are important lipid mediators regulating various reproductive processes in many species. In pigs, the expression pattern of PGE(2) and PGF(2 alpha) metabolic enzymes and the regulatory mechanism controlling PGE(2) and PGF(2 alpha) levels in the uterus during pregnancy are not completely understood. This study determined endometrial expression of the genes (PLA2-G4A, PTGS1, PTGS2, PTGES, PTGES2, PTGES3, AKR1B1, CBR1, and HPGD) involved in PGE(2) and PGF(2 alpha) metabolism during the estrous cycle and pregnancy and measured levels of PGE(2) and PGF(2 alpha) in uterine endometrial tissues and uterine flushings at the time of conceptus implantation in pigs. Except PTGES3, expression of the genes studied changed in a pregnancy-stagespecific manner, and localization of PTGES, AKR1B1, CBR1, and HPGD mRNAs were cell-type specific in the uterine endometrium. Levels of both PGE(2) and PGF(2 alpha) in uterine endometrial tissues and uterine lumen were higher on Day 12 of pregnancy than those of the estrous cycle and affected by different morphology of spherical and filamentous conceptuses. Furthermore, we determined that endometrial expression of AKR1B1, known to encode a PGF(2 alpha) synthase in other species, was increased by estrogen and interleukin-1beta and that AKR1B1 exhibited PGF(2 alpha) synthase activity in the porcine uterine endometrium. These results in pigs indicate that the PGE(2) and PGF(2 alpha) metabolic enzymes are expressed stage specifically in the endometrium during pregnancy and regulate the abundance of PGE(2) and PGF(2 alpha) in the uterus at the time of implantation and that AKR1B1 may act as a major PGF synthase in the endometrium during early pregnancy.