Non-genomic effect of steroids on oxytocin-stimulated intracellular mobilization of calcium and on prostaglandin F2α and E2 secretion from bovine endometrial cells

Progesterone (P4) was found to interfere directly with the interaction of oxytocin (OT) with its own receptor in bovine endometrium. The aim of these studies was to investigate whether other steroids have a similar effect. Endometrial slices and epithelial endometrial cells from days 14 to 18 of the estrous cycle were used. Progesterone (P4), pregnenolone (P5), 17β-hydroxyprogesterone (17-OHP4), the P4 receptor antagonist (aP4), and testosterone (T4) did not affect (P > 0.01) basal secretion of PGE2 and PGF 2α during 4 h of incubation but all steroids inhibited (P < 0.05) OT-stimulated PGF2α secretion both from endometrial slices and from dispersed cells. None of the steroids used affected OT-stimulated PGE2 secretion from the cells (P > 0.01). In the next experiment it was studied whether P5, 17-OHP4 and P4 pretreatment for 30 min modifies intracellular mobilization of Ca2+ in response to OT. Oxytocin induced a rapid increase in intracellular Ca2+concentrations within 15 s, while cells pretreated with steroids this increase occurred later. The total amount of intracellular Ca2+concentrations was lower (P < 0.05) in cells preincubated with steroids compared to controls. We conclude that steroids and aP4 are able to suppress OT-stimulated endometrial PGE2 and PGF2α secretion via a non-genomic pathway.