Genomic and non-genomic effects of progesterone and pregnenolone on the function of bovine endometrial cells

Progesterone (P4) decreases oxytocin (OT)-stimulated prostaglandin (PG)F2a, but not PGE2 secretion from bovine endometrial cells and this effect is partly elicited via a non-genomic route. The aim of this study was to determine whether P4 and pregnenolone (P5), in the presence or absence of OT, influence: (a) the gene expression of enzymes responsible for PGs synthesis: cyclooxygenase-2 (COX-2), synthase of PGF2a (PGFS) and PGE2 (PGES), (b) protein expression of COX-2, PGFS and PGES, and (c) P4 receptor membrane component 1 (PGRMC1) gene expression in bovine endometrial cells. The epithelial endometrial cells (2.5 x 105/ml) from Days 14-16 of the oestrous cycle were incubated for 72-96 h to attach the cells to the bottom of a well. Next, the cells were preincubated for 30 min with P4 and P5 (10-5M each) and incubated for 4 h and 6 h alone or with OT (10-7M). Thereafter, the medium was collected for PGE2 and PGFM determination, while cells were harvested for gene and protein expression analysis. The used steroids: (a) inhibited OT-stimulated PGF2a, but not PGE2 secretion from endometrial cells, (b) did not affect the expression of mRNA for COX-2, PGFS, PGES and PGRMC1 in endometrial cells after 4 and 6 h, (c) they decreased OT-stimulated COX-2 mRNA expression only after 6 h incubation, and (d) did not influence COX-2, PGFS and PGES protein expression after 6 h. These results indicate that P4 and P5 inhibit OT-stimulated secretion/production of luteolytic PGF2a by a transcription-independent mechanism and partly by down-regulation of COX-2 mRNA