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

Abstract

Progesterone (P<sub4</sub>) decreases oxytocin (OT)-stimulated prostaglandin (PG)F_2&alpha;, 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 PG_s synthesis: cyclooxygenase-2 (COX-2), synthase of PGF_2&alpha; (PGFS) and PGE=sub>2</sub> (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 × 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 PGF_2&alpha;, 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 PGF_2&alpha; by a transcription-independent mechanism and partly by down-regulation of COX-2 mRNA.