Stimulants of prostaglandin biosynthesis in human fetal membranes, uterine decidua vera and placenta

Dual inhibition of cyclooxygenase and lipoxygenase enzymes by human cerebrospinal fluid

Thromboxane A2 (TXA2) formed in damaged brain tissue and after thromboembolism and subarachnoid haemorrhage is responsible for cerebral vasospasm. In the present study, we examined the effect of human cerebrospinal fluid (CSF) on the production of thromboxane-A2 (TXA2) and 12-hydroxy-eicosatetraenoic acid (12-HETE) by human blood platelets. CSF was drawn by lumbar puncture from normal healthy volunteers (n = 17) and samples judged to be normal after routine examination in the clinical laboratories and were used fresh. We found that CSF inhibited the production of TXA2 and 12-HETE by blood platelets incubated with C14 labelled arachidonic acid (AA) in a concentration-related manner. Further biochemical analysis using proteolytic enzymes, gel filtration and membrane partition chromatography showed that the inhibitory activity was peptidic in nature and associated with a peptide of low molecular weight (1,400 Da). This study is the first to demonstrate that human CSF contains a dual inhibitor of cyclooxygenase (COX) and lipoxygenase enzymes in CSF.

Glutathione and glutathione-related enzymes in reproduction. A review

Glutathione and glutathione-related enzymes are pivotal for the normal functioning of several important biological processes in humans. Glutathione and glutathione-related enzymes are involved in the metabolism and detoxification of cytotoxic and carcinogenic compounds as well as reactive oxygen species. The role of reactive oxygen species in reproduction was the subject of many investigations, and there is compelling evidence for the involvement of these species in the physiology and pathology of both male and female reproductive systems. The glutathione/glutathione-related enzyme system was extensively studied in gynaecological oncology, but to a lesser extent in other topics related to reproduction. In this paper a review is provided on the glutathione/glutathione-related enzyme system in reproduction. Attention is given to its role as a detoxicating system, and as an early marker for disease.

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.

A product from human decidua inhibits prostaglandin production by human amnion

Human decidua was obtained from nonlaboring women after elective cesarean section. Decidua was incubated with media alone for 20 hours and this media (decidual conditioned media) was then incubated with amnion cells in monolayer culture and amnion rings. A 90% decrease in PGE2 production by amnion cells in monolayer culture was demonstrated in the presence of decidual conditioned media when compared to controls. In short term incubations with fresh amnion, decidual conditioned media decreased the production of PGE2 in amnion by greater than 25% of the control rate of production in 17 of 21 experiments. These observations suggest that human decidua produces a factor capable of inhibiting prostaglandin production by amnion.

Placental biosynthesis and metabolism of prostanoids: special reference to guinea-pig during the last third of gestation

Prostanoids are thought to take a prominent part in gestation and parturition physiology. Experiments were designed to determine the chronological alterations in placental synthesis and metabolism of prostanoids during the third trimester of gestation in the guinea-pig. Placental obtained at days 50, 55, 60, at term and after delivery were assayed (RIA and/or GC/MS) for PGE2, PGF2 alpha and TxB2 before (in vivo levels) or after 1 hour incubation (in vitro levels) for PGE2, PGF2 alpha, PGD2, TxB2, 6-keto-PGF1 alpha and PGF1 alpha. In addition, PGE2 and PGF2 alpha metabolism was measured by radiochromatography assay. No differences with gestational age were found in PGE2 and TxB2 in vivo levels but PGF2 alpha showed a slight increase around day 60. In contrast, in vitro levels of PGF2 alpha, TxB2 and PGE2 (in decreasing order of production) exhibited a marked increase from day 50 to delivery, whereas the other prostanoids showed no changes. Moreover, PGE2 and PGF2 alpha metabolism by the 15-hydroxyprostaglandin dehydrogenase was found to decrease during the same gestational period. These results are consistent with the idea that placenta in guinea-pig may be an important source of endogenous prostanoids and may contribute to the augmented intrauterine availability of prostanoids near parturition. The implications of these findings in relation to the mechanisms controlling synthesis and metabolism of prostanoids are discussed.

Endogenous stimulant of prostaglandin endoperoxide synthase activity in human amniotic fluid

In this study we describe the discovery and characterization of a substance in human amniotic fluid that stimulates prostaglandin biosynthesis by a microsome-enriched preparation of bovine seminal vesicles. The stimulatory activity is not retained substantially upon anisotropic ultrafiltration through a filter with a molecular weight exclusion limit of 500. Stimulation of prostaglandin biosynthesis by this substance is time- and concentration-dependent; maximal stimulation of approx. 200% being observed within 20 min of commencing incubation with 1 ml-equivalent of stimulant fraction. Stimulatory activity is demonstrable both in the presence of reduced glutathione (1.3 mM) and L-tryptophan (20 mM), either separately or combined, and in the presence of exogenous arachidonic acid (5-120 microM). In the absence of added cofactors, the stimulatory substance increases the rates of biosynthesis of prostaglandin E2 and prostaglandin F2 alpha to equal extents. The amount of stimulatory substance added to incubations is correlated positively with increased oxygen consumption during incubations. The stimulatory substance is stable to heating at 100 degrees C for 10 min but is inactivated substantially (to less than 20% of original activity) by treatment with pronase. It is concluded that human amniotic fluid contains a substance of relatively low molecular weight, which is proteinaceous in character, that stimulates prostaglandin endoperoxide synthase activity.

Inhibitory effects of dispersed human amnion cells on production rates of prostaglandin E and F by endometrial cells

Dispersed cells were prepared from amniotic membranes obtained either by caesarean section near term before labor (CS) or after spontaneous vaginal delivery (SL) and from human endometrial curettings. The cells were maintained separately in primary culture for about 18 h. Production rates (PR) of PGE and PGF during incubation for 1 h in defined medium were determined when the cell-types were separate (n = 60) or combined (n = 27) and when endometrial cells were incubated in medium conditioned by CS amnion cells (n = 13) or SL amnion cells (n = 12). The PR of PGE by CS amnion cells was five times greater than that of PGF and there was a two-fold increase (p less than 0.01) in PGE but not PGF by SL cells. Co-incubation was associated with a 25-32% fall in PR of both PGE and PGF (p less than 0.01) compared to the sum from separately incubated cells when CS cells were used whereas values for co-incubated SL cells did not differ from controls. Conditioned medium from CS but not SL cells inhibited PGE and PGF output by 30% and 40% (p less than 0.01) respectively. These findings suggest that human amnion cells release an inhibitor of prostaglandin synthesis in endometrial cells.

Increase in concentrations of prostaglandin endoperoxide synthase and prostacyclin synthase in human myometrium in late pregnancy

Concentrations of prostaglandin endoperoxide synthase (i.e. cyclooxygenase; PGH synthase) and prostacyclin synthase (PGI synthase) were quantified with specific radioimmunometric assays in human myometrium during the last trimester of pregnancy (n = 23) and in non-pregnant controls (n = 8). Pregnant myometrium contained 3 times more PGH synthase per mg microsomal protein than non-pregnant myometrium (p less than 0.01) but there was no increase with increasing gestational age in the third trimester nor with the onset of labor. In pregnancy, as compared to the non-pregnant state, there was no significant change in the PGI synthase content of myometrial microsomes, but significantly more PGI synthase was recovered in other subcellular fractions (p less than 0.01). This suggests that pregnancy affects preferential changes in the subcellular distribution of PGI synthase in myometrial cells. Relative to its PGI synthase content pregnant myometrium contained twice as much PGH synthase as non-pregnant myometrium (p less than 0.01). This may offer further evidence that PGH synthase rather than PGI synthase itself is the rate limiting factor in myometrial PGI2 production. On the other hand, the much larger increase in PGH synthase than in PGI synthase in pregnant as compared to non-pregnant myometrium, may serve to promote preferential synthesis of prostaglandins that are potent myometrial stimulants and of critical importance in human parturition.