Abstract:
In pigs, the exact mechanism for the shift in endometrial PGF<emph type="8">2α secretion from an endocrine toan exocrine mode during pregnancy recognition is not known. The objective ofthis study was to examine whether this shift involved a change in theresponsiveness of luminal epithelial, glandular epithelial and stromal cellsto 0 or 100 nM oxytocin. Luminal epithelial cells, glandular epithelial cellsand stromal cells were isolated from cyclic, pregnant or oestrogen-inducedpseudopregnant gilts on Day 12 (Experiment 1) or Day 16 (Experiment 2) postoestrus (oestrus = Day 0). For cells obtained on Day 12, oxytocinstimulated PGF<emph type="8">2α secretion bystromal cells (P<0.01) similarly for eachreproductive status, whereas oxytocin stimulated PGF<emph type="8">2α secretion from luminal andglandular epithelial cells (P<0.05) from pregnant andpseudopregnant gilts but not from cyclic gilts. For both concentrations ofoxytocin, mean PGF<emph type="8">2α secretionwas less (P<0.05) from stromal cells of pregnant thancyclic gilts. For cells obtained on Day 16, oxytocin stimulated PGF<emph type="8">2α release from stromal cells ofcyclic gilts but not from stromal cells of pregnant gilts. Mean PGF<emph type="8">2α secretion also was less(P<0.05) from stromal cells of pregnant gilts thancyclic gilts. Oxytocin tended to stimulate PGF<emph type="8">2α release(P<0.07) from glandular epithelial cells of cyclicbut not pregnant or pseudopregnant gilts. Luminal epithelial cells from allreproductive statuses were similarly unresponsive to oxytocin. In conclusion,the increased PGF<emph type="8">2α secretoryresponse to oxytocin of luminal and glandular epithelial cells from pregnantgilts on Day 12, combined with the decreased response of stromal cells frompregnant gilts on Days 12 and 16, may contribute, in part, to the shift inendometrial PGF<emph type="8">2α secretion froman endocrine to an exocrine direction during early pregnancy in pigs.