The high concentration of COX-2 transcripts found in bovine endometrium postpartum explains the fact that plasma PGFM concentrations in parturient cows are maximal on the day after delivery. At that stage, the stimulus for COX-2 expression probably derives from cytokines released from macrophages and other cells of the immune system that invade the uterus in response to the trauma inflicted on the tissues by fetal expulsion and placental separation. Moreover, a recent study demonstrated that PGE2, which is present in high concentrations in the uterine vasculature at birth, stimulates cytokine production in macrophages. flovent inhaler
In summary, bovine uterine tissues express predominantly the COX-2 isoform during pregnancy. COX-1 mRNA was detectable only in myometrium and caruncles. Placentomes had the highest concentrations of COX-2 transcripts among the tissues examined. Fetal cotyledons expressed COX-2 mRNA in significant amounts from Day 150 onward when maternal caruncles expressed COX-2 mRNA only very weakly. COX-2 transcripts in both tissues increased with advancing gestation and were strongly expressed at term but showed no significant difference before and after the onset of labor. Concentrations of COX-2 transcripts in endometrium, myometrium, and cervical mucosa were much lower than in the placentomes during the second half of gestation. A significant labor-associated increase in COX-2 mRNA concentration was observed in cervical mucosa; endometrium showed a marked increase on the day after parturition, and myometrial COX mRNA levels were variable both before and during parturition. Injection of OT induced a significant accumulation of COX-2 transcripts in endometrium, and it also induced significant release of PGE2 from cervical mucosa in vivo. Endogenous OT may therefore be responsible for the observed increase in endometrial PGF2a production during parturition, alone or in combination with cytokines of fetal or maternal origin; OT may also contribute significantly to release of PGE2 from cervical mucosa at parturition.