Fetal prostaglandin levels in twin pregnancies

PGE2 vs PGF2α in human parturition

Prostaglandin E2 (PGE2) and F2α (PGF2α) are the two most prominent prostanoids in parturition. They are involved in cervical ripening, membrane rupture, myometrial contraction and inflammation in gestational tissues. Because multiple receptor subtypes for PGE2 and PGF2α exist, coupled with diverse signaling pathways, the effects of PGE2 and PGF2α depend largely on the spatial and temporal expression of these receptors in intrauterine tissues. It appears that PGE2 and PGF2α play different roles in parturition. PGE2 is probably more important for labor onset, while PGF2α may play a more important role in labor accomplishment, which may be attributed to the differential effects of PGE2 and PGF2α in gestational tissues. PGE2 is more powerful than PGF2α in the induction of cervical ripening. In terms of myometrial contraction, PGE2 produces a biphasic effect with an initial contraction and a following relaxation, while PGF2α consistently stimulates myometrial contraction. In the fetal membranes, both PGE2 and PGF2α appear to be involved in the process of membrane rupture. In addition, PGE2 and PGF2α may also participate in the inflammatory process of intrauterine tissues at parturition by stimulating not only neutrophil influx and cytokine production but also cyclooxygenase-2 expression thereby intensifying their own production. This review summarizes the differential roles of PGE2 and PGF2α in parturition with respect to their production and expression of receptor subtypes in gestational tissues. Dissecting the specific mechanisms underlying the effects of PGE2 and PGF2α in parturition may assist in developing specific therapeutic targets for preterm and post-term birth.

Indomethacin blocks the immunosuppressive activity of rat testicular macrophages cultured in vitro

Macrophages are a prominent resident cell type in the interstitial tissue of the testis in several mammalian species. This presence in an immunologically-privileged site prompted an investigation of their ability to initiate and regulate lymphocyte proliferation in vitro. Isolated rat peripheral blood lymphocytes (PBL) were cultured either directly with isolated rat testicular (Tm) or peritoneal (Pm) macrophages or with the conditioned medium from cultures of these cells (Ts or Ps). The presence of Tm and Ts reduced the proliferative response of PBL to 65% +/- 3% and 65% +/- 4% of that observed in the control cultures. Stimulation of the Tm with lipopolysaccharide (LPS) did not significantly alter this effect. Dialysis of Ts (to remove molecules < 14,000 MW) before addition to PBL cultures did significantly reduce the amount of inhibition, with PBL proliferation reaching 93% +/- 4% of the control. LPS in conjunction with indomethacin (IDM) or interferon gamma (IFN gamma) induced PBL proliferation at levels comparable to or significantly greater than those of the controls (104% +/- 4% and 113% +/- 6%, respectively). The collective addition of IDM, IFN gamma and LPS to Tm cultures increased PBL proliferation over control levels (119% +/- 5% for Ts and 133% +/- 6% for Tm). Prostaglandin levels in macrophage-conditioned medium were measured by specific radioimmunoassay and were significantly greater in Ts (13.1 +/- 0.4 ng/ml PGE2 and 16.8 +/- 0.6 ng/ml PGF2 alpha) than in Ps (both below the assay minimum sensitivities). The results indicate that the rat testicular macrophages produce high basal levels of prostaglandin E2 and F2 alpha. These products appear largely responsible for the inhibition by these cells of mitogen-induced PBL proliferation in vitro, and may contribute to both the immune-privileged status and the normal physiology of the rodent testis.

Increased and intermittent prostaglandin release from amnion detected by a new superfusion technique for full thickness fetal membrane

Prostaglandin E2 (PGE) and F2 alpha (PGF) release by the intact fetal membranes is described using a novel superfusion technique allowing for the independent assessment of prostaglandin release from the amnion and chorio-decidua whilst maintaining the anatomical integrity of the fetal membranes. The effect of labour on prostaglandin release is described. Using this system it was confirmed that the amnion is a major site of prostaglandin release and possibly production. Labour resulted in a significant increase of both PGE and PGF release from the amnion side only (Pre-labour: PGE 918 pg/cm2/3h, PGF 370 pg/cm2/3h; Labour: PGE 2993 pg/cm2/3h, PGF 662 pg/cm2/3h). No change in either PGE or PGF release from the chorio-decidual side was observed in relation to labour. In addition a change in the pattern of prostaglandin release from the amnion was observed in tissues obtained after the onset of labour. In 6 of 8 samples obtained after spontaneous labour an intermittent or pulsatile release of both PGE and PGF was observed from the amnion side as compared to the steady state of prostaglandin release from all 10 samples obtained before labour.

The role of prostaglandins in the inhibition of cultured carcinoma cell growth produced by gamma-linolenic acid

The growth of the cultured human breast carcinoma cell line NUB 1 as well as that of other cultured malignant cells has been shown to be inhibited by addition of gamma-linolenic acid (GLA) to the culture medium. It has previously been suggested that these findings may be attributed to correction of a GLA deficiency in malignant cells, with supplementation of this fatty acid leading to increased prostaglandin (PG) production and consequent growth inhibition. To test this hypothesis the effect of 50 micrograms/ml concentrations of GLA and its sequential metabolite dihomo-gamma-linolenic acid (DGLA) and cell growth, morphology and prostaglandin (PGE and PGF) production by NUB 1 cells was investigated. GLA increased PGE and PGF production, inhibited cell growth and caused accumulation of lipid containing cytoplasmic granules. While treatment with DGLA increased PG production to a significantly greater extent than GLA administration it had no apparent effect on cell growth of morphology and did not inhibit cell growth. These findings suggest that some action other than the ability to increase PG production may be responsible for the inhibitory effects produced by GLA in malignant cells.

Differential regulation of prostaglandin production by inhibitors and stimulators in amniotic fluids during normal and dysfunctional labor

The regulatory effect of amniotic fluid factors on prostaglandin production by sheep seminal vesicle prostaglandin synthetase was determined using samples obtained before and after the onset of labor. Variations in the enzyme incubation conditions permitted the effects on both prostaglandin E (PGE) and prostaglandin F (PGF) production to be assessed. Amniotic fluid obtained before the onset of labor and during early labor resulted in a net stimulation of PGE production and no difference was observed between these two groups. Samples obtained before and during early labor had no net effect on PGF production. However, when samples obtained late in labor were tested, there was a greater stimulation of PGF and less of PGE compared to early labor suggesting a preference for PGF production rather than PGE in late labor. When samples obtained from patients in dysfunctional labor were compared to normal labor, no difference on the effect of either PGE or PGF production was observed. This implies that the decreased PGF previously described in dysfunctional labor is due to an intrinsic abnormality of the fetal membranes rather than inhibition of prostaglandin production by factors mediated via the amniotic fluid.

Immunoreactive oestrogens and progesterone in amniotic fluid in twin pregnancies

Amniotic fluid concentrations of immunoreactive oestrogens and progesterone were measured at the time of caesarean section in 32 twin pregnancies; 25 women had an elective section and seven were in labour at the time of operation. No significant differences between concentrations in the amniotic fluid of the first and second twin were found in respect of conjugated and unconjugated oestrone, oestradiol, oestriol, oestetrol and unconjugated progesterone either before or during labour. It is unlikely that changes in oestrogens or progesterone in the amniotic fluid are responsible for the selective changes seen in prostaglandins and fetal adrenal steroid during labour in the first twin.

Abnormal concentrations of prostaglandins in amniotic fluid during delayed labour in multigravid patients

Concentrations of prostaglandins E (PGE), F2 alpha (PGF), 13,14-dihydro-15-keto prostaglandin F2 alpha (PGFM), 6-keto F1 alpha and thromboxane B2 were measured by specific radioimmunoassay in samples of amniotic fluid from 22 multigravid patients during labour. Normal labour in 10 patients was associated with a significant increase of PGE, PGF and PGFM with close correlation to cervical dilatation (P less than 0.05). In the 12 patients with clinically delayed labour, in the absence of cephalopelvic disproportion, there were significantly lower PGF (P less than 0.002) and PGFM (P less than 0.05) concentrations obtained while no differences were observed in the other prostanoids measured. Administration of oxytocin to the latter group to enhance labour did not have any effect on the concentrations of prostaglandins obtained in spite of an improvement in intrauterine pressures and accelerated progress of labour.

Central venous concentrations of immunoreactive prostaglandins E, F, and 6-keto-prostaglandin F1 in eclampsia

Concentrations of prostaglandins E, F, and 6-keto-prostaglandin F1 alpha were estimated in central venous blood and amniotic fluid in 21 women with eclampsia and 16 healthy pregnant controls. Central venous blood concentrations of 6-keto-prostaglandin F1 alpha and prostaglandin E were significantly lower in patients than controls before delivery and remained reduced for at least 48 hours after delivery. Low concentrations of prostaglandins E and 6-keto-prostaglandin F1 alpha are probably directly related to the pathogenesis of eclampsia.

Twin pregnancy as a model for studies in fetal cortisol concentrations in labour: relation to prostaglandins, prolactin and ACTH

Cortisol and prostaglandins were measured in umbilical cord blood obtained from 50 twin pregnancies at caesarean section performed either before or during labour. Umbilical artery cortisol concentrations did not differ between twin I and II before labour or in the latent stage. During active labour cortisol levels were significantly higher in twin I than in twin II. Maternal cortisol levels did not correlate with cord blood cortisol levels in either twin before active labour, nor did the rise in maternal cortisol correlate with the cortisol level in twin I; maternal cortisol levels did, however, correlate with cortisol levels in twin II during active labour. Prostaglandins E(PGE), F 2 alpha (PGF 2 alpha), 13,14-dihydro-15-keto F 2 alpha (PGFM) and ACTH were measured in cord vein blood. PGE values did not differ between twin I and II before active labour. During active labour PGE levels were significantly greater in twin I and correlated with raised cortisol levels. No differences were seen at any stage in PGE and PGFM levels between twins I and II although PGFM levels increased in both twins during active labour. ACTH and prolactin levels did not increase during labour and were similar in twins I and II. The rise in fetal cortisol during active labour is primarily of fetal origin and PGE may be involved in stimulating cortisol production in the fetus.

The lecithin/sphingomyelin ratio in twin pregnancies

The lecithin/sphingomyelin ratio showed no difference between the two amniotic sacs in 24 multiple pregnancies examined before the onset of labor. Once labor started, however, the L/S ratio was higher in the first sac compared to the second in the six pregnancies where labor had commenced and was somewhat advanced at the time of amniocentesis. Dual-sac amniocentesis is essential during labor when assessment of pulmonary maturity is required, whereas single-sac sampling is adequate before the start of labor.

Fetal adrenal gland maturation in growth-retarded twin pregnancies

Twenty-two twin pregnancies each with one growth-retarded and one normal twin fetus were examined to determine the effects of fetal growth retardation on the maturation of the adrenal gland with respect to cortisol and dehydroepiandrosterone sulphate (DHEAS). The growth-retarded twin fetuses (IUGR) had lower umbilical arterial concentrations of DHEAS than their siblings (IUGR 5.25 +/- 2.4; non-IUGR 6.51 +/- 2.9 mumols/l; p less than 0.01), whereas cortisol concentrations were not statistically different (no labor, IUGR 1,134 +/- 751, non-IUGR 1,140 +/- 958 mumols/l; labor IUGR 2,062 +/- 929, non-IUGR 1,609 +/- 469 mumols/l). These data suggest that while the definitive zone of the fetal adrenal is as well-developed as in non-growth-retarded twins, the fetal zone shows reduced secretory capacity of delta 5-steroids. This supports the hypothesis that in growth retardation the adrenal gland shows features of increased maturation.