Metabolism of platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in human fetal membranes and decidua vera

We have previously reported that platelet-activating factor (PAF) is present in human amniotic fluid obtained from women in labor. We have also demonstrated that PAF, lyso-PAF, and alkyl acyl-sn-glycero-3-phosphocholine (AA-GPC) are present in human amnion tissue. In the reported study, we have investigated the enzymes involved in PAF metabolism in amnion tissue and their regulation. A phospholipase A2 activity has been demonstrated in amnion tissue which cleaves alkyl acyl (long-chain) sn-glycero-3-phosphocholine. The enzyme activity is not altered by Ca2+ and is distinctly different from the phospholipase A2 that we have previously characterized in this tissue. Amnion tissue contains acetyltransferase activity which requires Ca2+ and is associated with the microsomal fraction. Acetylhydrolase is also present in the cytosolic fraction of amnion tissue. Acetylhydrolase activity has also been demonstrated in amniotic fluid. The affinities of acetyltransferase (for lyso-PAF) and acetylhydrolase (for PAF) were unaffected by Ca2+. In the presence of Ca2+, however, the specific activity of acetyltransferase was increased four- to fivefold while that of acetylhydrolase was unaffected. Acetyltransferase and acetylhydrolase activities in fetal membranes and decidua were similar and were unchanged with gestational age. The possible role of PAF in the initiation of human parturition is discussed.

Sulfohydrolase activity for estrone sulfate and dehydroepiandrosterone sulfate in human fetal membranes and decidua around the time of parturition

We examined the distribution and kinetic parameters of sulfohydrolase activity in human amnion, chorion, and decidua using estrone sulfate (E1S) and dehydroepiandrosterone sulfate as substrates. Amnion contained low levels of sulfatase activity. Chorion had active sulfohydrolase activity for both substrates, but a significantly greater maximum velocity (Vmax) for E1S. The Km was not different between the two substrates. However, there was a slight but statistically significant decrease in Km and increase in Vmax for sulfohydrolase activity using E1S in chorion from patients delivering vaginally after the spontaneous onset of labor compared to those delivering by elective cesarean section before the onset of labor but at a similar gestational age. Decidua possessed sulfohydrolase for E1S with similar Km and Vmax as chorion. There were no changes occurring around the onset of labor. Using dehydroepiandrosterone sulfate as substrate, the decidua had a similar Km as the chorion, but its Vmax was significantly less. In both tissues for both substrates, the enzyme had highest specific activity in the 105,000 X g pellet, with almost no activity in the soluble fraction. The greatest total sulfohydrolase activity was contained in the 800 X g pellet despite several methods of homogenization and washing of the 800 X g pellet. We conclude that the sulfohydrolase activity of human chorion and decidua may be an important factor in regulating free steroid levels within the pregnant uterus. The significant change in the kinetic parameters of E1S sulfatase may partially explain the increased ability of chorion to hydrolyze E1S which occurs in association with the spontaneous onset of labor.

Infection and phagocytosis as possible mechanisms of rupture in premature rupture of the membranes

The concept that premature rupture of the membranes is due to an infectious process is well accepted. However, no definitive data implicating a particular microorganism or a mechanism of action have been advanced. By the use of our recently developed experimental in vitro amnion-chorion reaction vessel model we have studied the effect of the peroxidase-hydrogen peroxide-halide antimicrobial system on these membranes. We have noted that amnion, chorion, decidua, and placental macrophages all possess peroxidase activity. Tissues collected from deliveries following labor (vaginal) are significantly higher in activity than those collected from deliveries with no labor (cesarean section). A mobilization of enzyme from macrophages to amnion appears to occur in the laboring patient. Increased protein hydrolysis is noted in membranes collected from patients without labor subjected to the peroxidase-hydrogen peroxide-halide cytotoxic system when compared with membranes from laboring patients. Bursting pressures of membranes collected from patients without labor are shown to be decreased when the membranes were incubated in the presence of lysolecithin or in the presence of amniotic fluid and phospholipase A2.

Activity of lysosomal hydrolases in human placenta, amnion, decidua and myometrium in the 2nd and 3rd trimester

Six lysosomal hydrolases were studied in tissues of human placenta, amnion, decidua, and myometrium obtained in the 2nd and 3rd trimester. No significant increase in the activity of any lysosomal hydrolase was found in the 3rd-trimester values compared with those obtained in the 2nd trimester. Thus, the increased activity of lysosomal hydrolases in maternal serum at term, previously described in several studies, seems not to be paralleled by a corresponding increase in the activity of these enzymes in the tissues of the pregnant uterus. We speculate that the increase in maternal serum towards term may reflect a macrophage activation initiated by elevated estrogen concentrations in the 3rd trimester.

The isolation and characterization of lysozyme from human foetal membranes: a comparison with the enzyme from other sources

Lysozyme (muramidase) was isolated from an acidic extract of human foetal membranes by adsorption and elution from octadecyl silica. It was further purified by gel-filtration and ion-exchange. The final product was homogeneous by high performance liquid chromatography (h.p.l.c.) and electrophoresis. It was indistinguishable from human milk lysozyme by all criteria investigated, including amino acid composition, electrophoretic mobility, retention time on h.p.l.c. and sequence of the first nine residues. Human uterine decidual tissue was shown to contain a similar concentration of lysozyme to foetal membranes. The enzyme was also present at lower concentrations in amnion, placenta and amniotic fluid.

Purification and characterization of a lysophospholipase from human amnionic membranes

We have identified the presence of a lysophospholipase in human placental tissues and have purified this enzyme from the amnion. The specific activity was highest in the amnion and decreased across adjacent tissues. The purification involved the use of DEAE-Sephadex, phenyl-Sepharose, hydroxylapatite, and sulfylpropyl Sephadex chromatography. The activity of the purified enzyme toward palmitoyl lysophosphatidylcholine is 2.5 mumol min-1 mg-1 and the pH optimum is 7.0. The enzyme is not inhibited by EDTA and does not appear to have a metal ion requirement. The enzyme may be of membrane origin; the purified enzyme requires the presence of detergent during storage. The effects of substrate composition and physical state on enzymatic activity were explored. The enzyme was not active toward mono-, di-, or triglycerides, nor toward diacyl phospholipid. The enzyme was active toward myristoyl and palmitoyl lysophosphatidylcholine at concentrations where these substrates spontaneously form micelles or where Triton X-100 was used to induce co-micellization of the substrate at low concentrations with detergent. A role for this enzyme in processing the lysophospholipid product of phospholipase A action must be considered in evaluating arachidonic acid production in human fetal membranes and placental tissue, particularly during the initiation of labor.

Uterine Adenylate Cyclase Activity During the Estrous Cycle and Early Progestation in the Rat: Responses to Fluoride Activation and Decidual Induction

Uterine adenylate cyclase (AC) activity of the rat was measured by radiochemical analysis during the estrous cycle and early pseudopregnancy. During the estrous cycle, AC activity increased from 4.6 to 16.9 pmol cAMP formed/min X mg protein between metestrus and proestrus. Although AC was activated 2- to 3-fold at all cycle stages by 10 mM NaF, the resulting pattern of activity was similar to that measured in the absence of fluoride. The results demonstrated that the pattern of AC activity during the cycle was similar to that of other estrogen-sensitive uterine enzymes and that the ovarian hormones probably altered enzyme biosynthesis and turnover to a greater extent than activation and kinetic properties. Following the induction of pseudopregnancy by cervical stimulation, enzymic activity increased from 3.5 to 9.4 pmol between Days 1-4 (Day 1=leukocytic vaginal smear) and declined thereafter. AC activity was increased 2- to 5-fold by NaF on all days. AC activity was similarly increased by a mechanical trauma to the uterus, but only when the trauma was applied on Day 4. Following trauma to the uterus, AC activity was not increased further by NaF. The similarities between the physicochemical characteristics of AC during the estrous cycle and early progestation suggested that the enzyme during all endocrine states had virtually identical properties. However, the transient sensitivity to activation after trauma on Day 4 was unique to progestational uteri. Because the properties of enzyme were not altered by the endocrine state of the tissue, the transient sensitivity to activation by trauma was suggested to be a result of hormone-induced alterations in the membrane in which AC is sequestered.

Diamine oxidase activity in human decidua and endometrium

The activity of diamine oxidase, the enzyme that catalyzes the oxidative deamination of putrescine, spermidine, histamine, and other substances involved in the regulation of cell proliferation and immune responses, increases up to 1000-fold in blood of pregnant women. In vivo experiments have shown that progestins stimulate diamine oxidase in the rodent uterus. We examined diamine oxidase activity in human endometrium at different phases of the menstrual cycle and in decidua from first-trimester pregnancies. Enzyme activity was also assayed in tissues and media of cultured human endometrium and decidua in the presence of estradiol or medroxyprogesterone acetate. Enzyme activity in first-trimester decidual tissues (286 +/- 86 mU of diamine oxidase per milligram of DNA; mean +/- SEM) was considerably higher (p less than 0.001) than that in endometrium (2.6 +/- 1.6), and the activity increased from 6 to 17 weeks of pregnancy. No significant differences were detected in proliferative and secretory endometrium. Activities in media of endometrium in organ culture generally were below detectability. Decidua secreted large amounts of the enzyme into the medium (160 to 600 mU per milligram of DNA per day), greatly exceeding the initial tissue activities. Bovine serum, when added to culture media, caused a marked increase in diamine oxidase levels, whereas estradiol (10(-8) mol/L) or medroxyprogesterone acetate (10(-6) mol/L) did not. Kinetic analysis showed a Michaelis constant of 7.4 X 10(-6) mol/L with putrescine as the substrate. Spermidine and histamine were competitive inhibitors of putrescine with an inhibition constant of 1.1 X 10(-4) and 3.5 X 10(-6) mol/L, respectively. These results demonstrate synthesis and export of diamine oxidase by decidua in organ culture, stimulation of activity by serum factors, and competition of histamine, spermidine, and putrescine for the enzyme.

Purification and properties of gamma-glutamyl transpeptidase from rat deciduoma

gamma-Glutamyl transpeptidase has been purified by chromatographic methods from endometrium of rat deciduoma. The membrane-bound enzyme, digested with papain, eluted as a single fraction during chromatography and the final preparation had a specific activity of 104.5 U/mg protein. The molecular weight of the native enzyme was approximately 70,000 and the protein could be resolved into a heavy and a light fraction on sodium dodecyl sulfate-acrylamide gel electrophoresis with molecular weights of 45,000 and 23,000, respectively. The enzyme had a pH optimum of 8.2 and Km's for donor (p-nitroanilide) and acceptor (glycylglycine) were 1 and 7.6 mM, respectively. The enzyme was inhibited by L-serine in the presence of borate with a Ki of 22 microM. The decidual enzyme was not heat stable and its electrophoretic mobility was decreased after neuraminidase treatment.

Purification of prostaglandin E2-9-oxoreductase from human decidua vera

Prostaglandin E2-9- oxoreductase (PGE2-9-OR), the enzyme which converts prostaglandin E2 (PGE2) to prostaglandin F2 alpha (PGF2 alpha), has been detected in human decidua vera. A 105-fold purification was achieved when the centrifuged homogenate was fractionated sequentially by DEAE-Trisacryl, hydroxyapatite-agarose gel, ultrogel AcA 44 and Matrex gel blue A gel chromatographies. The following kinetic constants for PGE2-9-OR have been obtained. The equilibrium constant with respect to PGE2 is 83 microM, the Michaelis constant, Km, for PGE2 is 80 microM, for NADPH 1.6 microM. The maximal velocity for the forward reaction is V1 = .203 pmol/min. The enzyme was inhibited by progesterone, oestradiol-17 beta, cortisol and pharmaceutical drugs. An activating effect could be demonstrated with Ca2+ and oxytocin. The occurrence of PGE2-9-OR in the decidua vera suggests that this enzyme may be responsible for the transformation of PGE2 to PGF2 alpha in these tissues. This may be an important mechanism for the initiation and maintenance of uterine contractions.

The identification and characterization of protein kinase C activity in fetal membranes

Protein kinase C activity was demonstrated in cytosolic fractions prepared from human amnion and decidua vera tissues. The enzyme has been partially purified and was found to be glycerophospholipid-dependent. Phosphatidylserine was most active in the stimulation of protein kinase C. Ca2+ was also required for the expression of the enzyme activity. In the presence of unsaturated diacylglycerols, maximum activation of protein kinase C was observed at suboptimal concentrations of Ca2+. A possible role of phospholipid-dependent protein kinase C in the regulation of arachidonic acid release in this tissue is discussed.

Development and characteristics of an oestrogen sulphotransferase in placenta and uterus of the pregnant mouse. Comparison between mouse and rat

The mouse placenta possesses a soluble oestrogen sulphotransferase activity which increases markedly from at least 12 days of gestation until term. At about 16 days of gestation, a similar activity is found in the uterus. This activity also increases until term and disappears rapidly post partum. The uterine enzyme activity appears to require the presence of the foetal unit for its onset, since unoccupied horns, whether their endometrial stromal cells are differentiated to decidual cells or not, are essentially devoid of it. Uterine cytosols from non-pregnant mice are also inactive in this respect. In late gestation, the uterine sulphotransferase is confined to the decidua basalis, the areas to which the placentas are attached. The sulphotransferase(s) of placenta and uterus has an absolute requirement for 3'-phosphoadenosine 5'-phosphosulphate, and possesses little activity in the absence of exogenous thiol groups. Stimulation is also seen in the presence of Mn2+, Mg2+ or Ca2+. Oestrone and oestradiol, and to a lesser degree oestriol, are substrates for the enzyme(s), whereas testosterone, cortisol and dehydroepiandrosterone are not. Oestrone and oestradiol at higher concentrations (1.0-1.5 microM) completely inhibit the enzyme(s). These enzymes could play a role in altering tissue concentrations of active oestrogens during gestation in the mouse. Oestrogen sulphotransferase activity is low or absent in reproductive tissues of the pregnant rat.

Characterization of catechol-O-methyltransferase activity in human uterine decidua vera tissue

In the present investigation, we characterized the activity of catechol-O-methyltransferase (COMT) in homogenates prepared from human decidua vera tissue. The specific activity of COMT in decidua vera is greater than that in liver and myometrium and much greater than that in adipose tissue and erythrocytes. The specific activity of COMT in decidua vera obtained at term was significantly greater (p less than 0.001) than that obtained early in gestation. However, we do not as yet ascribe physiologic significance to this finding since the period of time between delivery of the tissue and assay of the enzyme activity may have varied between the two groups.

Characterization of ornithine decarboxylase activity in human uterine decidua vera

Ornithine decarboxylase (ODC) catalyzes the rate-limiting step in the biosynthesis of the polyamines putrescine, spermidine, and spermine. In the present study, we characterized the activity of ODC in human uterine decidua vera tissue. We evaluated the activity of the enzyme in decidua vera tissue that was obtained from pregnancies at term before or after the spontaneous onset of labor and in decidua vera tissue that was obtained between 8 and 18 weeks' postconceptional gestational age at the time of elective abortion. Among these tissues, no significant differences in ODC activity were demonstrable.

Changes in uterine phosphatase levels in mice treated with aristolic acid during early pregnancy

Aristolic acid (AA) exerted interceptive activity in mice. A single oral dose of aristolic acid at the dose levels of 120 and 90 mg/kg on Day 1 or Day 6 of pregnancy in mouse resulted in a rise of acid phosphatase (AP) and fall of alkaline phosphatase (ALP) and protein in uterus in both groups. Both delta 5-3 beta-hydroxy-steroid dehydrogenase (delta 5-3 beta-HSD) and glucose 6-phosphate-dehydrogenase (G6PD) of ovaries remained unaltered. Exogenous progesterone (1 mg s.c., Days 5-8) administered along with aristolic acid (on Day 6 only) could neither protect pregnancy nor prevent the biochemical changes produced in the uterus due to drug treatment. This unaltered steroidogenesis and alteration in alkaline phosphatase, acid phosphatase and protein gives some insight into the mechanism of action of the compound aristolic acid.

Production of active and inactive renin by cultured explants from the human female genital tract

Myometrium, decidua, chorio-decidua and amnion were collected from women undergoing caesarean section and from pregnant women at hysterectomy and hysterotomy for comparison with myometrium, cervix and endometrium taken from non-pregnant women at hysterectomy. Homogenates of chorio-decidua and amnion contained the largest concentrations of active and inactive renin. Cultured explants of all tissues except amnion were found to produce both types of renin. The percentage of active renin produced before 20 days of culture was significantly greater in cultures of chorio-decidua than in those of myometrium (P less than 0.0005) or decidua vera (P less than 0.025), which suggests that renin synthesis in vivo is probably confined to the chorio-decidua.

The variations of estrogen receptor, progesterone receptor, cAMP, ODC activity and RNA synthesis of deciduomata in pseudopregnant rats

The present study was done to define the conditions of implantation of fertilized ovum from serial day-to-day changes in the tissue weight of deciduomata in pseudopregnancy, estrogen receptor (ER), progesterone receptor (PR), cAMP content, RNA synthesizing capacity and ornithine decarboxylase activity (ODC). Pseudopregnancy was induced in Wistar rats in the estrus morning by vaginocervical stimulation. At the 4th day of pseudopregnancy deciduomata was induced by intraluminal instillation of olive oil with simultaneous oophorectomy and intramuscular injection of 20 mg progesterone depot (the day of induction of decidualization was arbitrarily expressed as D0 and the ensuing days, as D1, D2 and so on). The number of binding sites of ER and PR was estimated by exchange assay using dextran charcoal. cAMP content and RNA synthesizing capacity were determined by RIA and 3H-UTP uptake, respectively. ODC activity was measured by the method of Jänne and Williams-Ashman. Following the induction of deciduomata the uterus weight (unilateral) increased abruptly to 2-fold at D2 and approximately 30-fold (4.5 g) at D8 and declined thereafter. ER diminished in a linear fashion from 2.77 x 10(-10) M at D2 to 0.53 x 10(-10) M at D7. On the other hand, PR was estimated 2.9 x 10(-10) at D2. 2.5 x 10(-10) M at D5 and decreased further at D6 and D7, cAMP was 77 nmoles/mg protein at D2 and decreased rapidly from D3 onward. RNA synthesizing capacity declined in a linear fashion from D3 to 1/2 to D5 and 1/3 at D7. ODC was found 1.7 CO2 nmoles/mg protein at D2, decreased at D3 and D4, but remained nearly the same at D4 and D5.

Plasminogen activator activity in mouse embryos cultured on decidual cell monolayers

The nature of proteolytic activity in the mouse blastocyst was investigated in vitro using cell monolayers as a substrate. Blastocysts obtained from mice on day 4 of gestation were placed directly on various types of cell monolayers. The embryos had hatched at 34 hrs, attached at 45 hrs, and at 56 hrs of culture they formed trophoblast outgrowths by displacing the underlying monolayer cells. Because blastocysts developed equally well on all types of cell monolayers tested, a decidual cell monolayer was used in all the following experiments. The plasminogen activator activity in blastocysts was examined using the fibrin-agar overlay assay. There was a strong relationship between the levels of activity and the extent of trophoblast outgrowth. At the hatching stage, 20% of the embryos showed fibrinolysis, whereas 86% showed clear fibrinolysis at the trophoblast outgrowth stage. After the loss of invasiveness, only 32% of them showed fibrinolysis. Lysed zones surrounding trophoblast always extended beyond the area which displaced the previously occupied cell monolayer. We never observed a clear zone (halo) between the trophoblast and monolayer cells nor cytolytic activity inside the fibrinolytic zone until the embryos had lost their invasive nature.

Cortisol:cortisone interconversion by human decidua in relation to parturition: effect of tissue manipulation on 11 beta-hydroxysteroid dehydrogenase activity

Cortisol:cortisone interconversion was studied in human decidua obtained from three groups of patients at term (37-42 weeks): before the onset of labour (at elective Caesarean section), after labour of spontaneous onset, and after labour of induced onset. When intact tissue was incubated with [3H]cortisol or [3H]cortisone in phosphate buffer without added substrate or cofactors, cortisone to cortisol was the dominant conversion. However, when damaged cells or tissue homogenates were used in the same conditions, the dominant direction of the reaction was reversed, with a large increase in oxidative (cortisol to cortisone) activity. Cortisol:cortisone interconversion was similar in the three groups of samples using either intact tissue or homogenates, as was the total 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) activity measured in tissue homogenates in the presence of added substrate (cortisol or cortisone) and cofactors (NADP+ or NADPH). Endogenous cortisol concentrations in decidua were higher than those of cortisone, and the ratio of cortisol to cortisone was similar in the three groups. These findings suggest that there are no changes in human decidual 11 beta-HSD activity in relation to parturition. Specific activity of 11 beta-HSD decreased at high protein concentrations, suggesting the presence of some enzyme inhibitor(s) in homogenized decidual tissue.

Corticosteroid metabolism in vitro by human placenta, fetal membranes and decidua in early and late gestation

Corticosteroid conversion by early (7 to 10 weeks) and late (36 to 42 weeks) human placenta, fetal membranes and decidua was studied. Tritiated cortisol, cortisone, corticosterone, 11-dehydrocorticosterone (DHC) and 11-deoxycorticosterone (DOC) were incubated in vitro with homogenates of these tissues and extracts chromatographed on Sephadex LH20 columns. 11 beta-hydroxysteroid dehydrogenase activity (11 beta-HSD; EC 1.1.1.146) was present in all these tissues from as early as the seventh week of pregnancy. In the fetal membranes the enzyme activity was present in the chorion, the amnion showing no activity. Only the decidua could convert cortisone and DHC to the biologically more active cortisol and corticosterone, respectively. DOC was not transformed by any of the tissues. No 11 beta-HSD activity was found in amniotic fluid, retroplacental serum, umbilical cord plasma or cord tissue.

Diacylglycerol metabolism and arachidonic acid release in human fetal membranes and decidua vera

Diacylglycerol lipase activity has been demonstrated in human fetal membranes and decidua vera tissues. The specific activity of the enzyme is highest in the microsomal fraction of decidua vera tissue. The acylester bond at the sn-1 position of 1,2-diacyl-sn-glycerol is hydrolyzed followed by release of the fatty acid at the sn-2 position. The diacylglycerol lipase activity present in the microsomal fraction of decidua vera tissue hydrolyzes preferentially a diacylglycerol containing an arachidonoyl group in the sn-2 position. Monoacylglycerol lipase activity was also demonstrated in these tissues. The specific activity of monoacylglycerol lipase was significantly greater than that of diacylglycerol lipase and catalyzed preferentially the hydrolysis of monoacylglycerols containing an arachidonyl group in the sn-2 position. Based on the subcellular distribution and the differential effects of various inhibitors, we suggest that the monoacylglycerol lipase and diacylglycerol lipase in decidua vera tissue are 2 distinct enzymes. Diacylglycerol kinase specific activity was examined also and was found to be 4-5 times greater in amnion than in either chorion laeve or decidua vera. The importance of diacylglycerol metabolism in the mechanism of arachidonic acid release and prostaglandin biosynthesis is discussed.

Trapped blood elements within the decidua of the rat pregnant uterus generate a lipoxygenase product(s) which inhibits myometrial prostacyclin synthesis

1 Prostacyclin (PGI(2)) production by chopped segments of rat pregnant uterus was low compared with synthesis by separated myometrial tissue. Incubation of separated myometrium with decidua (2:1 by weight) led to an inhibition of myometrial PGI(2) output.2 Boiling decidual tissue abolished the inhibitory influence on myometrial PGI(2) output. Preincubation of decidua with 5,8,11,14-eicosatetraynoic acid (ETA) (30 mug/ml) also suppressed decidual inhibitory activity but indomethacin (30 mug/ml) was ineffective.3 Incubation of decidual and myometrial tissue with arachidonic acid (AA) 10 mug/ml did not increase the inhibition of myometrial PGI(2) synthesis, even if the decidua were pre-incubated with indomethacin.4 Myometrial PGI(2) production was reduced if the chopped tissue was pre-incubated with soya bean lipoxidase for 10 min at 4 degrees C. This reduction was reversed if the lipoxidase was incubated with ETA (30 mug/ml) for 30 min at 37 degrees C before addition to the myometrial tissue.5 Perfusion of the uterus to remove blood elements removed the inhibitory action that the decidua exerted upon myometrial PGI(2) production. PGI(2) synthesis by separated decidual and whole uterine tissue was markedly elevated.6 The addition of rat blood platelets (0.75 x 10(9)/ml) to incubations of perfused decidual tissue reduced PGI(2) output and restored the inhibitory action that the decidua exerted on myometrial PGI(2) synthesis.7 It is concluded that a lipoxygenase enzyme contained in blood platelets trapped within the decidual vasculature produces a hydroperoxy acid which inhibits decidual PGI(2) production or myometrial PGI(2) synthesis when the tissues are incubated together. It is suggested that perfusion is a pre-requisite before study of PGI(2) synthesis in highly vascularised tissues.8 The pathophysiological importance of such platelet lipoxygenase products is discussed.

Phosphatidylinositol-specific phospholipase C in fetal membranes and uterine decidua

An assay procedure was developed in which phosphatidyl[2-(3)H]inositol was employed as substrate for the measurement of phosphatidylinositol-specific phospholipase C activity. Employing this assay, phosphatidylinositol-specific phospholipase C activity in human fetal membranes and uterine decidua was identified and characterized. The specific activity of this enzyme in amnion (4.4 mumol x mg(-1) protein x h(-1)) was three times that in uterine decidua and more than five times that in chorion laeve. No difference was found between the specific activity of phosphatidylinositol-specific phospholipase C in placental amnion and that in reflected amnion. The products of phosphatidylinositol hydrolysis in short-term incubations were stoichiometric amounts of diacylglycerol and inositol-1,2-cyclic-phosphate plus inositol-1-phosphate. After longer periods of incubation, monoacylglycerol also was detected. Diacylglycerol lipase activity also was demonstrated in these tissues. More than 90% of phosphatidylinositol-specific phospholipase C activity of amnion tissue was recovered in the 105,000-g supernatant fraction, and optimal enzymatic activity in vitro was observed at pH 6.5-7.5 in the presence of Ca(2+) (8 mM) and mercaptoethanol (4 mM). Phosphatidylinositol-specific phospholipase C activity was stimulated by fatty acids in low concentrations, but was inhibited by lysophosphatidylcholine and a variety of detergents. No effect of labor on the specific activity of phosphatidylinositol-specific phospholipase C in either fetal membranes or uterine decidua could be detected. The finding of an active phosphatidylinositol-specific phospholipase C activity in human fetal membranes and uterine decidua is complementary to our previous finding of a selective loss of arachidonic acid from phosphatidylinositol of human fetal membranes during labor. The action of phosphatidylinositol-specific phospholipase C, coupled to diacylglycerol lipase action, could provide a mechanism for the release of arachidonic acid for prostaglandin biosynthesis during parturition.

Initiation of human parturition. XII. Biosynthesis and metabolism of prostaglandins in human fetal membranes and uterine decidua

Prostaglandin synthetase activity was assayed in homogenates prepared from human fetal membranes and uterine decidua tissues with [14C] arachidonic acid used as substrate. In amnion, chorion laeve, and decidua vera tissues obtained after the spontaneous onset of labor and vaginal delivery the mean specific activities of prostaglandin synthetase were respectively 1.47, 0.53, and 0.39 nmoles x hr-1 x gm-1 tissue; in these same tissues obtained at elective cesarean section before the onset of labor the mean specific activities of prostaglandin synthetase were respectively 0.61, 0.33, and 0.28. The specific activity of prostaglandin synthetase of amnion (but not chorion laeve or decidua vera) was significantly greater in samples obtained after labor than in those obtained before labor (p less than 0.02). Prostaglandin synthesis in amnion, chorion laeve, and decidua vera was inhibited by acetylsalicylic acid and by indomethacin. Prostaglandin E2 was formed in amnion and chorion laeve, whereas prostaglandin E2 and prostaglandin F2 alpha were formed in decidua vera. The activity of NAD+ -dependent 15-hydroxyprostaglandin dehydrogenase was also assayed and the specific activities of this enzyme in chorion laeve and decidua vera tissues obtained before and after labor were high, whereas 15-hydroxyprostaglandin dehydrogenase activity in amnion was low.

The distribution of polyamine oxidase activity in the fetomaternal compartments

Polyamine oxidase activity was measured in different compartments of the feto-maternal unit by a radiochemical method. The activity in the retroplacental serum (mainly of intervillous origin) was 20 to 30 times higher than in maternal uterine or peripheral venous blood sera. No activity was found in the fetal cord blood sera. The enzyme level in the maternal peripheral sera fell to undetectable levels within 72 hours post partum. Preliminary data indicate that the enzyme might be produced by the decidua rather than by the placenta. It is suggested that the enzyme may constitute an important part of a supposed local immunological barrier formed at the placental bed to help to protect the fetal allograft from maternal immune rejection through a local suppressive effect on maternal cellular immunity.

Observations on the origins of plasma membrane in rat deciduoma

An NADH-ferricyanide reductase activity resistant to inactivation by cytochemical procedures was examined during decidualization of rat endometrium. Resistant activity was restricted to plasma membranes, distal elements of the Golgi apparatus, and discoid cisternae and cytoplasmic vesicles of decidual cells of endometrium of the pseudopregnant rat on days 3, 4, 5, 7, and 9, after mating. The procedure reduced or eliminated any evidence of NADH-ferricyanide reductase activity from other cellular components such as endoplasmic reticulum, nuclei, and mitochondria. The observations of the glutaraldehyde-resistant reductase in both plasma membranes and discoid cisternae may indicate a role for the latter in the biosynthesis of plasm membranes during decidualization when massive cell proliferation and membrane biosynthesis occur. The origin of the discoid cisternae is tentatively ascribed to the mature faces of the Golgi apparatus.

Enzyme analysis of mouse extra-embryonic tissues

We have separated for enzyme analysis the following layers that surround the conceptus at midgestation: decidua, trophoblast, parietal endoderm (including Reichert's membrane), visceral endoderm, yolk-sac mesoderm and amnion. Measurement of several catabolic enzyme activities (N-acetyl-beta, D-hexosaminidase, beta-glucuronidase, alkaline and acid phosphatases and non-specific esterases) in these tissues indicates that they are biochemically distinct, perhaps reflecting the different functions that they perform in providing the embryo proper with a desirable environment for differentiation and development. Our studies also provide an example of how visceral endoderm cells can effectively block passage of maternal macromolecules (in this case a serum esterase) in the fetal circulation. Finally, since there is often difficulty in distinguishing among early embryonic and extra-embryonic cell types produced in teratocarcinoma cultures, we have considered how our observations might be of use in the respect, particularly in discriminating between visceral and parietal endoderm.

Changes in uterine phosphatase levels in mice deprived of LH during early pregnancy

Mice injected with normal rabbit serum on Day 4 of gestation showed a progressive increase in specific alkaline and acid phosphatase activities on Days 6 and 7. Mice injected with antiserum to LH on Day 4 showed a significant decrease in specific alkaline phosphatase activity estimated biochemically on Days 6, 7 and 8, but this decrease was histochemically evident only on Day 8. Similarly, acid phosphatase activity in antiserum-treated mice was significantly increased on Days 6, 7 and 8 when estimated biochemically, but only on Day 8 when studied histochemically.

Adenylate cyclase from human decidua parietalis

Adenylate cyclase (EC 4.6.1.1) activity was demonstrated in membrane fractions of human decidua parietalis. Adenylate cyclase activity was associated with membrane fractions of decidua but not chorion or amnion. Prostaglandins PGE1 and PGE2 but neither PGD2 nor PGF2 alpha stimulated this activity at gestational ages 18 to 40 weeks. Fluoride and guanosine triphosphate stimulated decidual adenylate cyclase; however, epinephrine-stimulated adenylate cyclase activity was demonstrable only in the presence of guanosine triphosphate. The possible roles of adenylate cyclase activity in the decidua are discussed.

[Studies on the activities of glycogen synthetase and glycogen phosphorylase in the human endometrium (author's transl)]

Glycogen content, glycogen synthetase and glycogen phosphorylase were studied in the endometrial tissues of 28 women with normal menstrual cycles and in the decidual tissues of 24 women with normal early pregnancies. The endometrial glycogen synthetase enzyme increased gradually from the proliferative phase to the secretory phase and reached maximal activity during the sixteenth to twenty-third days of the cycle, a time coincident with maximal glycogen content, while the glycogen phosphorylase reached its maximal activity on and after the twenty-fourth day of the cycle. In addition, glycogen phosphorylase activity in the decidual tissue during the early period of gestation (4--10 weeks) was lower than that in the endometrial tissue during the late secretory phase of the cycle, and in particular, the active form (-AMP) was significantly (p less than 0.005) low, with the result that the glycogen content in the decidua was significantly (p less than 0.05) higher than that in the endometrium. On the other hand, in 20 normal pregnant women during the 6--10th weeks of gestation, the glycogen contents in the decidua and in the placental villi were 599 +/- 44 mg/100 g wet weight (mean +/- standard error of the mean) and 731 +/- 55 mg/100 g, respectively, but the difference between them was statistically not significant. The levels of glycogen synthetase and glycogen phosphorylase enzyme in the decidua were significantly (p less than 0.005) higher than those in the placental villi.

Initiation of human parturition. X. Substrate specificity of phospholipase A2 in human fetal membranes

The substrate specificity of phospholipase A acitivty of fetal membranes and uterine decidua was investigated with the use of synthetic substrates, and emphasis was on the specificity of fatty acid esters in the sn-2 position of glycerophospholipids. Rat liver mitochondria were also used as an enzyme source for the substrate specificity studies. Phosphatidylethanolamine was found to be hydrolyzed more rapidly than was phosphatidycholine by the phospholipase A activities of human fetal membranes and uterine decidua and of rat liver mitochondria. The phopholipase A2 in fetal membranes preferentially effected the hydrolysis of phosphatidylethanolamines containing specific fatty acids in the sn-2 position in the following order: arachidonic acid greater than oleic acid less than palmitic acid. No remarkable specificity for arachidonyl esters in the sn-2 position of phosphatidylethanolamines was observed for the phospholipase A activities of human uterine decidua or rat liver mitochondria. The results of this study are consistent with the view that human fetal membrane phospholipase A2 that preferentially hydrolyzes the phosphatidylethanolamines that contain arachidonic acid in the sn-2 position is, in part, responsible for the highly selective accumulation of free arachidonic acid in the amniotic fluid of women in labor.

[Decidualisation of the endometrial stromal cell. An electron microscopic study (author's transl)]

The fine structural changes of the endometrial stromal cell from late secretory phase up to full developed decidua cell have been investigated by means of electron microscope. During decidual transformation the cell volume, the assortment of cytoplasmic organelles and the mode of intercellular attachments undergo characteristic alterations. These alterations reflect an adaptation on new cellular functions. In contrast to the structural organization, which is transformed continuosly, the encymatic cell pattern exerts a step wise gradual transformation, since new encymatic capacities can only arise after their funtional structures have been established. To the most important functions of decidua cells and their prestages belong secretory and endocrine activities. Precollagen fibrills represent a specific secretory product of the stroma reticulum cells. The active involvement of the full differentiated decidua cells in steroid metabolism is indicated by characteristic transformation of the cytoplasmic organization concomittantly to the appearance of intracellular steroid dehydrogenase activities. So-called karyosoma could be demonstrated within the nuclei of postovulatory stromal reticulum cells as in decidua cells. Similar nuclear differentiations have been observed in various target cells of steroid hormones. They possibly are structural manifestations of the hormonal interaction with the nuclear DNA.

Phospholipase A activity in human and ovine uterine tissues

Phospholipase A was assayed in crude lysosomal fractions of human decidua, amnion, chorion and myometrium. Activity was present in all the tissues and was highest in decidua and amnion which contained enzymes with pH optima of 6.5-8.0 and 7.2 respectively. Comparison of the activities in tissues obtained before labor with others obtained during labor showed no differences. In sheep, the fetal membranes contained a greater activity of phospholipase A than placenta and myometrium. Stimulation of the fetal adrenals with corticotrophin caused a marked increase in activity in both amnion and chorioallantois. It is concluded that the human amnion and the ovine amnion and chorioallantois could participate in the biosynthesis of prostaglandins by releasing stored arachidonic acid.

Progesterone and estrogen control of uterine prostaglandin dehydrogenase activity during deciduomal growth

Prostaglandin, dehydrogenase activity was determined in deciduomal and myometrial tissues during growth and regression of the deciduoma during pseudopregnancy. The hormonal control of prostaglandin dehydrogenase activity in these tissues was determined in experiments with ovariectomized pseudopregnant rats. Prostaglandin dehydrogenase activity for both prostaglandin E1 (PGE1) and prostaglandin F2alpha (PGF2alpha) in deciduomal and myometrial tissues increased during the growth of the deciduoma and decreased during the regression phase. No prostaglandin dehydrogenase activity was detected in non-decidualized pseudopregnant rat uteri. In ovarictomized pseudopregnant rats, progesterone and estrogen increased prostaglandin dehydrogenase activity for PGE1 in the deciduoma and myometrium; no synergistic action of the hormones was observed. Progesterone increased prostaglandin dehydrogenase activity for PGF2alpha in the deciduoma, but had no effect in the myometrium. The increases during decidualization in dehydrogenase activity for PGE1 and PGF2alpha, and the enhanced inactivation of these luteolytic substances would provide an explantation for the prolonged pseudopregnancy which results from decidualization of the uterus.

Prostaglandin synthesis in decidual tissue of the rate uterus

Prostaglandin (PG) synthetase activity and tissue concentration were measured in unilateral deciduomata induced by traumatization of the pseudo-pregnant rat uterus and in the decidua of pregnancy. PG synthetase activity per unit weight of deciduoma tissue was 7-10 fold higher, throughout the life-span of the deciduoma, than that in the untraumatized control horn. The concentration of prostaglandins of the E-type in the deciduoma exceeded that found in the control uterine horn by a factor of 10-20 on days 3-4 after decidual induction, and about five-fold on days 9-10. The concentration of prostaglandins of the F-type in the deciduoma measured on days 4 and 8 did not differ significantly from that in the control horn.

Initiation of human parturition. II. Identification of phospholipase A2 in fetal chorioamnion and uterine decidua

In this study, the presence of a phospholipase has been demonstrated in the human chorioamnion and uterine decidua. That the chorioamnionic enzyme is of the phospholipase A2 type was established by product identification following the incubation of the enzyme with either radioactive phosphatidylcholine or phosphatidylethanolamine. The potential relationship between the expression of the activity of this enzyme and the regulation of arachidonic acid release, prostaglandin formation, and the initiation of labor is considered.

Metabolism of prostaglandins within the pregnant uterus

The metabolism of E and F prostaglandins has been studied in both fetal and maternal tissues obtained from the pregnant human uterus. Both 15-hydroxyprostaglandin dehydrogenase and 13,14-prostaglandin reductase are shown to be widely distributed in these tissues. Comparison of the levels of enzyme activity in different tissues demonstrates that the greatest metabolism of prostaglandins takes place in the membranes and placenta and that there is much less in the myometrium and the decidua. The lowest enzyme activity was found in the umbilical cord, and no metabolism could be demonstrated in amniotic fluid or in umbilical venous blood. The significance of these findings is discussed.

Delta5,3beta-hydroxysteroid dehydrogenase activities in rat trophoblast and ovary during pregnancy

Delta5,3beta-Hydroxysteroid dehydrogenase (3beta-HSD) activity has been measured in homogenates of ovary and trophoblast from 9th to 21st day pregnant rats under conditions where there was little or no further metabolism of the progesterone formed from pregnenolone. Trophoblast 3beta-HSD activity is first detectable on the 11th day of gestation; the specific activity peaks on the 13th day, and falls thereafter. The ovary enzyme activity rises gradually to the 19th day and falls on the 21st day. Decidua homogenates contain very low levels of 3beta-HSD activity, while embryo and yolk sac homogenates do not posses significant amounts. Total 3beta-HSD activities were also determined on a per conceptus basis. At no time during pregnancy does the total trophoblast 3beta-HSD activity exceed 40% the activity of the ovary. This may explain why the progesterone-producing capacity of trophoblast in the rat is inadequate to support normal pregnancy following ovariectomy. The temporal patterns of trophoblast and ovary 3beta-HSD activity suggest that the enzymes are not coordinately controlled in the two tissues.

Work in progress. Occurence of phospholipase A1 and A2 in human decidua

Phospholipase A2, an enzyme which may regulate the formation of polyunsaturated fatty acids utilized for prostaglandin synthesis, was found to have significant higher activity in decidual than in myometrial tissue. The major part of phospholipase A2 in the decidua had an acid pH optimum, which indicates that most of the enzyme is stored in the lysosomes of this tissue. These findings, together with previous observations, lend further support to the view that lysosomal phospholipase A2 released within decidual cells might be a trigger of abortion and parturition.

[Thymidylate synthetase in the antimesometrial and mesometrial portions of decidual tissue under normal conditions and following application of the antifolate preparation chloridine]

Specific activity of thymidylate synthetase (TMS) under normal conditions and after the action of pyrimethamine was investigated in antimesometrial (A) and mesometrial (M) parts of rat decidua. On the 9th-11th days of pregnancy specific activity of TMS in the A part proved to be higher than in the M part of decidua, and the former one reached its maximum by the 10th day. Specific activity of TMS in the M part decreased gradually from the 9th to 11th days of gestation. Pyrimethamine, applied on the 9th day of pregnancy caused a wave-like increase in the specific activity of TMS in the A part; this elevation was not so pronounced in the M part; A study of the physico-chemical properties of TMS from the decidua and the embryos of rats showed that the enzyme had a molecular weight of 58000, an optimal pH of 6.9, and could be quickly inactivated by heating.

Metabolism of prostaglandin F2alpha within the human uterus in early pregnancy

The potential for intra-uterine metabolism of prostaglandins in early pregnancy was studied by incubation of prostaglandin F2a (PGF2a) with tissues obtained by termination hysterectomy at 7 and 16 weeks gestation. Enzymes regulating the degradation of prostaglandins were demonstrated in placenta and membranes and to a lesser extent, in myometrium and decidua. It is believed that these enzymes may have a physiological role in maintaining the continuity of pregnancy, and that the high degradation of PGF2a in placenta and membranes may be one of the reasons that, for termination of pregnancy, far higher doses are required intra-amniotically than extra-amniotically.