Expression of Key Prostaglandin Synthases in Equine Endometrium During Late Diestrus and Early Pregnancy

Abstract Luteolysis in domestic species is mediated by the release of luteolytic pulses of prostaglandin (PG) F2α by the uterus at the end of diestrus, which must be suppressed by the conceptus to permit maternal recognition of pregnancy. In many species, including the horse, both the conceptus and the endometrium also synthesize PGE2, which may antagonize PGF2α by playing a luteotropic and/or antiluteolytic role. While the release of PGE2 and PGF2α by the equine endometrium in late diestrus and early pregnancy has been previously studied, the underlying prostaglandin synthase gene regulatory mechanisms remain poorly defined. To resolve this issue, cyclooxygenase-2 (COX-2), microsomal PGE2 synthase (PGES), and PGF2α synthase (PGFS) expression were examined in a series of endometrial biopsies obtained from cycling mares on Days 10, 13, and 15 postovulation, as well as from pregnant mares on Day 15. Quantification of COX-2 expression revealed significant (P < 0.01) increases in both mRNA and protein levels ...