Oxytocin-stimulated phosphoinositide hydrolysis and prostaglandin F-2 alpha secretion by luminal epithelial, glandular epithelial and stromal cells from pig endometrium. II. Responses of cyclic, pregnant and pseudopregnant pigs on days 12 and 16 post oestrus

In pigs, the exact mechanism for the shift in endometrial PGF(2 alpha) secr etion from an endocrine to an exocrine mode during pregnancy recognition is not known. The objective of this study was to examine whether this shift i nvolved a change in the responsiveness of luminal epithelial, glandular epi thelial and stromal cells to 0 or 100 nM oxytocin. Luminal epithelial cells , glandular epithelial cells and stromal cells were isolated from cyclic, p regnant 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(2 alpha) secretion by stromal cells (P< 0.01) similarly for each reproductive status, whereas oxytocin stimulated P GF(2<alpha>) 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(2<alpha>) secretion was less (P<0.05) from stromal cells of pregnant than cyclic gilts. For cells obtained on Da y 16, oxytocin stimulated PGF(2<alpha>) release from stromal cells of cycli c gilts but not from stromal cells of pregnant gilts. Mean PGF(2 alpha) sec retion also was less (P<0.05) from stromal cells of pregnant gilts than cyc lic gilts. Oxytocin tended to stimulate PGF(2<alpha>) release (P<0.07) from glandular epithelial cells of cyclic but not pregnant or pseudopregnant gi lts. Luminal epithelial cells from all reproductive statuses were similarly unresponsive to oxytocin. In conclusion, the increased PGF(2<alpha>) secre tory response to oxytocin of luminal and glandular epithelial cells from pr egnant gilts on Day 12, combined with the decreased response of stromal cel ls from pregnant gilts on Days 12 and 16, may contribute, in part, to the s hift in endometrial PGF(2 alpha) secretion from an endocrine to an exocrine direction during early pregnancy in pigs.