Relative transcript abundance of oxytocin receptor gene in porcine uterus during luteolysis and early pregnancy.

The aim of the present study was to investigate transcript localization of the oxytocin receptor (OTR) gene in different cells of the porcine uterus during luteolysis and early pregnancy (days 14-16) using in situ hybridization (ISH). OTR mRNA was localized in the uterine luminal epithelium (LEC), glandular epithelium (GEC), stromal cells (SC) of the endometrium, in the longitudinal muscle layer (LM) and circular muscle layer (CM) of the myometrium. The OTR transcript was quantified by optical density units of silver grains. The OTR transcript levels in the endometrium and myometrium were statistically higher during luteolysis than during early pregnancy (P<0.05). Besides, during luteolysis, the mRNA level was higher in the LEC, GEC of the endometrium and LM of the myometrium compared to that observed in the SC of endometrium and CM of the myometrium, respectively (P<0.05). In summary: 1) the level of OTR mRNA in uterine tissues is higher during luteolysis compared to early pregnancy, 2) the OTR transcript level in endometrial cells did not correspond to the sensitivity of these cells to oxytocin (OT), 3) the myometrial expression of the OTR gene is appropriate to control contractile activity and secretion of PG during luteolysis.