J. G. Bibby

Specific production of prostaglandin E by human amnion in vitro

Abstract Prostaglandin production by intra-uterine human tissues has been investigated using a method of tissue superfusion. Tissues were obtained at elective Caesarean section and after spontaneous vaginal delivery. It was found that all the tissues studied (amnion, chorion, decidua and placenta) produced more prostaglandin E (PGE) and 13,14-dihydro-15-keto-prostaglandin F (PGFM — the major circulating metabolite of prostaglandin F) than prostaglandin F (PGF). Amnion produced significantly more PGE (but not PGF or PGFM) than any other tissue. Prostaglandin production by each tissue was similar whether it was taken at elective Caesarean section or after spontaneous vaginal delivery.

Possible role for prostacyclin in human parturition

Human amnion, chorion, decidua and placenta produced 6-oxo-PGF1alpha when superfused in vitro. Furthermore amnion, an avascular tissue, produced more 6-oxo-PGF1alpha after labour than all other tissues investigated and its production of 6-oxo-PGF1alpha was significantly greater after labour than before the onset of labour. These findings suggest that prostacyclin production by foetal membranes may have a role in the mechanisms controlling human parturition. Moreover, this is the first evidence for the production of prostacyclin by an avascular tissue.

A comparison of plasma prostaglandin levels in term and preterm labour

Peripheral plasma levels of 13,14‐dihydro‐15‐keto‐prostaglandin F (PGFM) were determined in women during pregnancy and in term and preterm labour. The PGFM concentrations at term were not significantly different from the levels between 26 and 34 weeks gestation. In both term and preterm labour there was a rise in PGFM levels with increasing cervical dilatation although the mean values tended to be lower during preterm labour. These findings may provide an explanation for the effectiveness of prostaglandin synthetase inhibitors in suppressing myometrial activity in preterm labour.

PROSTAGLANDINS IN THE HUMAN UMBILICAL CIRCULATION AT BIRTH

Prostaglandin E (PGE), prostaglandin F (PGF) and 13, 14‐dihydro‐15‐keto‐prostaglandin F (PGFM) have been measured in umbilical cord plasma obtained immediately after delivery of the baby before clamping of the cord. In general the prostaglandin levels followed the pattern PGFM>PGE>PGF. A significant arterio‐venous difference was demonstrated only for PGE with raised venous levels (P<0.01). In cord blood samples obtained from infants whose mothers had received epidural anaesthesia, no arterio‐venous difference for PGE could be demonstrated although the mean levels were not significantly different from controls. The concentrations of prostaglandins in Umbilical cord plasma proximal to the placenta were found to rise continuously from the time of delivery of the baby with no significant changes after cord clamping or placental delivery. The possible physiological significance of these findings is discussed.

PROSTAGLANDINS IN UMBILICAL PLASMA AT ELECTIVE CAESAREAN SECTION

Prostaglandin E (PGE), prostaglandin F (PGF) and 13,14‐dihydro‐l5‐keto‐prostaglandin F (PGFM) have been measured in umbilical cord plasma obtained immediately after delivery by elective Caesarean section. Umbilical venous plasma levels of PGE were significantly greater than the corresponding arterial levels (p <0.02); there were no significant arterio‐venous differences for PGF or PGFM. In general, concentrations of PGFM exceeded those of PGE which in turn were greater than concentrations of PGF. Umbilical venous levels of PGE and both arterial and venous levels of PGF and PGFM were significantly greater after spontaneous labour with vaginal delivery than after elective Caesarean section.

MELATONIN IN THE MATERNAL AND UMBILICAL CIRCULATIONS DURING HUMAN PARTURITION

The concentration of melatonin in maternal peripheral plasma was measured during late pregnancy, term and pre‐term labour. There was a small increase in the mean concentration of melatonin during labour which was significant in term labour. Umbilical arterial and venous plasma, whether obtained at term, after spontaneous vaginal delivery or at Caesarean section, contained significantly greater concentrations of melatonin than maternal plasma. A significant arterio‐venous difference was demonstrated for both groups of umbilical samples with raised venous levels after spontaneous vaginal delivery but higher arterial levels at Caesarean section.

The effect of cervical encerclage on plasma prostaglandin concentrations during early human pregnancy.

In women having either cervical encerclage under general anaesthesia or a vaginal examination in the early second trimester of pregnancy, peripheral plasma levels of 13,14‐dihydro‐l5‐keto prostaglandin F (PGFM) were measured before and after each procedure. A significant rise in circulating levels of PGFM was found within minutes of completing cervical encerclage but not after vaginal examination or induction of general anaesthesia.

PLASMA STEROID CHANGES IN PRE‐TERM LABOUR IN ASSOCIATION WITH SALBUTAMOL INFUSION

Serial measurements of peripheral plasma concentrations of progesterone and oestradiol‐17β were made in 23 women with singleton pregnancies who were given intravenous salbutamol in an attempt to inhibit pre‐term labour. Mean levels of both hormones fell significantly during salbutamol infusion but returned to pre‐treatment levels after therapy was stopped. Plasma human placental lactogen concentrations did not change during salbutamol infusion, suggesting that the fall in steroid hormone levels was unlikely to be an effect of altered uterine or placental blood flow.

SPECIFIC PRODUCTION OF PROSTAGLANDIN E BY HUMAN AMNION IN VITRO

Prostaglandin production by intra-uterine human tissues has been investigated using a method of tissue superfusion. Tissues were obtained at elective Caesarean section and after spontaneous vaginal delivery. It was found that all the tissues studied (amnion, chorion, decidua and placenta) produced more prostaglandin E (PGE) and 13,14-dihydro-15-keto-prostaglandin F (PGFM - the major circulating metabolite of prostaglandin F) than prostaglandin F (PGF). Amnion produced significantly more PGE (but not PGF or PGFM) than any other tissue. Prostaglandin production by each tissue was similar whether it was taken at elective Caesarean section or after spontaneous vaginal delivery.