Prostaglandin production by porcine allantochorion in vitro: effect of cortisol infusion in vivo
The effect of cortisol infusion into the porcine fetus on subsequent prostaglandin (PG) production in vitro by the fetal placenta (the allantochorion) was studied. Also, the possible in vitro effects of glucocorticoids and other steroids on PG production by dispersed cells were examined. Two fetuses in each of 6 sows were catheterized on day 100 or 101 of gestation (normal gestation is 114–116 days); one was infused with cortisol (6 mg/day) and one with saline for 5 days beginning on day 103. On day 108, fetal allantochorionic tissue was aseptically collected from the infused fetuses and 2 uninfused litter mates (controls). Pieces of tissues were cut from the allantochorion (4 sows) and dispersed cell preparations were made from each fetus (4 sows). Each preparation was cultured for 24 h, and the production of PGE2, PGF2α, and 6-keto-PFG1α (prostacyclin metabolite) measured. In vivo cortisol infusion had no significant effect on the in vitro production of PGE2 or PGF2α by tissues or dispersed cell preparations. However, tissue from the fetuses infused with cortisol produced significantly less 6-keto-PGF1α than uninfused controls (54% of control, p < 0.05). The dispersed cells from uninfused fetuses and 2 cortisol-infused animals were also incubated for 24 h with 10−7 and 10−9 M concentrations of estrone, estradiol, progesterone, cortisol, and dexamethasone, and the production of PGE2, PGF2α, and 6-keto-PFG1α was measured. No significant effect of any of these steroids in vitro on prostanoid production was observed. These studies indicate that prolonged in vivo cortisol exposure inhibits prostacyclin production by the allantochorion but that this effect cannot be reproduced by short-term (24 h) in vitro incubations with cortisol. Cortisol may be one of the factors responsible for the decreased prostacyclin production by allantochorion previously reported to occur during labor in this species.Key words: labor, prostaglandins, glucocorticoids, pig, allantochorion.