Gestational profile of prostaglandin E2 synthesis by porcine placenta and fetal membranes.

The capacity of the diffuse, epitheliochorial porcine placenta (chorioamnion plus endometrium: AMCE and chorioallantois plus endometrium: ALCE) and allantoamnion (ATA), obtained from sows at 47-112 days of gestation (n = 12), to release PGE2, during in vitro explant incubation, was determined. There was no significant difference between PGE2 release from AMCE and ALCE, and the data obtained from these two tissues were pooled. The release of PGE2 from ATA was, at all stages of gestation, significantly less (8-50 fold; p less than 0.01, n = 12) than that released from AMCE/ALCE. During gestation, the basal release of PGE2 from AMCE/ALCE increased from 13.7 +/- 2.8 pmol/100 mg per incubation (n = 8; mean +/- S.E.M.) at less than 80 days to a maximum of 176.5 +/- 30.9 pmol PGE2/100mg per incubation (n = 10) at greater than 109 days of gestation. Basal PGE2 release from ATA increased from 1.6 +/- 0.6 pmol PGE2/100 mg per incubation (n = 3) at less than 80 days to 3.5 +/- 0.5 pmol PGE2/100 mg per incubation at greater than 109 days gestation. At all stages of gestation and in all tissues, the addition of sodium arachidonate significantly stimulated PGE2 release, indicating that during gestation prostaglandin synthesis by porcine placenta and fetal membranes is, at least partly, substrate limited. The observed increase in the release of prostaglandin E2 from placenta and fetal membranes that occurred from 90 days of gestation and rapidly increased at term may reflect an increase in substrate availability, an increase in the activity of prostaglandin endoperoxide H synthase- E isomerase or a combination of these processes.