Abstract Estrogen affects transcriptional status by activating its corresponding nuclear receptor, the estrogen receptor (ER). It can also induce rapid cellular reactions within a few minutes, and this feature cannot be explained by the transcription-mediated effects of estrogen. The latter mechanisms are called 'non-genomic actions' of estrogen. In contrast, the former classic modes of action came to be called 'genomic actions'. One of the recent developments of research on estrogen was the substantiation of the non-genomic actions of estrogen; these were initially observed and reported as intriguing phenomena more than 40 years ago. The interacting molecules as well as the biological significance of non-genomic actions have now been shown. In the field of genomic actions, invention and spread of new technologies, including high-throughput sequencers, promoted a comprehensive view of estrogen-mediated transcriptional regulation.
Progesterone (P4) acts through different actuating pathways called genomic and non-genomic pathways. Here we investigated whether P4 regulates prostaglandin (PG) F2? (PGF) and PGE2 production in bovine endometrium through different pathways. Cultured endometrial cells were exposed to P4 for a short time (5-20min) or bovine serum albumin (BSA)-conjugated P4 (P4-BSA) for 24h. Progesterone treatment for 24h stimulated PGE2 production in epithelial cells, but suppressed both PGF and PGE2 production and the expression of PG-metabolising enzymes including phospholipase A2 (PLA2) and cyclooxygenase-2 (COX2) in stromal cells. Short-term (5-20min) P4 treatment did not affect PLA2 or COX2 transcript levels in either cell type. P4-BSA increased PGF and PGE2 production only in epithelial cells. Nuclear P4 receptor mRNA expression in endometrium was higher at the follicular phase than at the early- to mid-luteal stages, whereas membrane P4 receptor mRNA expression did not change throughout the oestrous cycle. The overall results suggest that P4 controls PG production by inhibiting enzymes via a genomic pathway and by stimulating signal transduction via a non-genomic pathway. Consequently, P4 may protect the corpus luteum by attenuating PGF production in stromal cells and by increasing PGE2 secretion from epithelial cells.