Oxytocin-stimulated phosphoinositide hydrolysis and prostaglandin F2α secretion by luminal epithelial, glandular epithelial and stromal cells from pig endometrium. II. Responses of cyclic, pregnant and pseudopregnant pigs on Days 12 and 1

Abstract

In pigs, the exact mechanism for the shift in endometrial PGF _2α secretion from an endocrine to an exocrine mode during pregnancy recognition is not known. The objective of this study was to examine whether this shift involved a change in the responsiveness of luminal epithelial, glandular epithelial and stromal cells to 0 or 100 nM oxytocin. Luminal epithelial cells, glandular epithelial cells and stromal cells were isolated from cyclic, pregnant or oestrogen-induced pseudopregnant gilts on Day 12 (Experiment 1) or Day 16 (Experiment 2) post oestrus (oestrus = Day 0). For cells obtained on Day 12, oxytocin stimulated PGF_2α secretion by stromal cells (P<0.01) similarly for each reproductive status, whereas oxytocin stimulated PGF _2α secretion from luminal and glandular epithelial cells (P<0.05) from pregnant and pseudopregnant gilts but not from cyclic gilts. For both concentrations of oxytocin, mean PGF_2α secretion was less (P<0.05) from stromal cells of pregnant than cyclic gilts. For cells obtained on Day 16, oxytocin stimulated PGF _2α release from stromal cells of cyclic gilts but not from stromal cells of pregnant gilts. Mean PGF _2α secretion also was less (P<0.05) from stromal cells of pregnant gilts than cyclic gilts. Oxytocin tended to stimulate PGF _2α release (P<0.07) from glandular epithelial cells of cyclic but not pregnant or pseudopregnant gilts. Luminal epithelial cells from all reproductive statuses were similarly unresponsive to oxytocin. In conclusion, the increased PGF_2α secretory response to oxytocin of luminal and glandular epithelial cells from pregnant gilts on Day 12, combined with the decreased response of stromal cells from pregnant gilts on Days 12 and 16, may contribute, in part, to the shift in endometrial PGF_2α secretion from an endocrine to an exocrine direction during early pregnancy in pigs.