Prostaglandins are important mediators of reproductive function. However, comparative differences in functional prostanoid receptors during gestation and postpartum are not fully explored. The aim of this study was to compare the responsiveness to PGF2α, PGE2, and U46619 in the rat uterine horn at late gestation and postpartum. Rats were sacrificed at late gestation (n=56) and at postpartum (n=56). Uterine horns were opened longitudinally, cleared of foetuses and placentae and divided into three segments (upper (ovarian end), middle and lower (cervical end)). Tissue from each segment was immersed in organ baths containing Krebs buffer at 37°C, pH 7.4 with 1 µM indometacin, gassed with 95%O2/CO2 and attached to isometric force transducers (Hutchinson et al., 2003). After 30 minutes equilibration cumulative concentration-effect curves were performed (10-9 M to 10-5 M) for PGF2α, PGE2, and U46619. Data were recorded as area under the curve and expressed as a percentage of the reference contraction (hypotonic shock) (Fischer et al., 2008).
Results were expressed as arithmetic means±SEM and statistically analysed using two-way ANOVA with Bonferronis post-hoc test. PGF2α, PGE2, and U46619 evoked concentration dependent excitability in both gestational and postpartum tissue. PGF2α significantly increased contractility in postpartum tissue compared to late gestation at 105M between the upper (P<0.05) and middle segments (P<0.01) and at 105M and 106M between the lower segments (P<0.001). PGE2 and U46619 significantly enhanced activity in upper segment postpartum tissue compared to late gestation at 105M (P<0.05 and P<0.001 respectively) but no differences between the two tissues in mid and lower segments were observed. The results suggest that prostaglandin EP and TP receptors are upregulated in a topographical manner but the FP receptor is uniformly enhanced at postpartum. Regional regulation of prostanoid receptors at postpartum may help in uterine involution whereas the upregulation of the FP receptor may help prevent postpartum hemorrhage.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.