Role of platelet-activating factor (PAF) in the ovoimplantation in the rat: effect of the specific PAF-acether antagonist, BN 52021

Effects of Ginkgo biloba extract on the embryo-fetal development in Wistar rats

BACKGROUND

Ginkgo biloba extract (GBE) is an herbal medicine used for treating neurodegenerative diseases, cerebrovascular insufficiency, peripheral arterial occlusive disease, and also vestibular disturbance. Some components of GBE have presented estrogenic effects and, in a previous study, high dosages of GBE caused intra-uterine growth retardation in fetuses of Wistar rats treated during the fetogenesis period.

METHODS

Pregnant Wistar rats were treated, through gavage, with different dosages of aqueous GBE (3.5, 7.0, and 14.0 mg/Kg/day), during the tubal transit and implantation period. Rats were killed on the 15th day of pregnancy and the following parameters were evaluated: clinical symptoms of maternal toxicity; maternal body weight; feed and water intake; maternal liver, kidney, and ovary weights; number of corpora lutea; implants per group ratio; pre- and post-implantation loss per group ratio; live fetuses mean; dead fetuses percentage; fetus and placenta weight per offspring ratio; and fetal external malformation.

RESULTS

No significant alteration was found for both the maternal and embryonic parameters evaluated.

CONCLUSIONS

The GBE treatment in pregnant Wistar rats, during the tubal transit and implantation period, caused no toxic effect on the maternal organism and did not induce embryonic death, growth retardation, and/or fetal malformations.

The role of platelet-activating factor in the mammalian female reproductive tract

Platelet-activating factor (PAF) is a potent lipid mediator produced by various cell types of mammals and is involved in an inflammatory-like process with increased vascular permeability. Platelet-activating factor exerts its actions through the activation of specific PAF receptors (PAF-R) found in cells and tissues of the female reproductive tract. The aim of this article was summarized briefly in the current research on the role of PAF in female reproductive functions. Platelet-activating factor has been implicated in processes of ovulation, implantation and parturition because of its angiogenic and growth factor properties. This factor is influenced by ovarian steroid hormones in bringing about changes in the uterus and is a candidate molecule for initial embryo-maternal dialogue. Tissue concentrations of PAF are regulated by the equilibrium between biosynthesis and degradation by PAF-acetylhydrolase (PAF-AH). Antagonists of PAF interfere with ovulation and implantation. Platelet-activating factor, its receptor, and PAF-AH activity play an important role in the maintenance of pregnancy.

The role of paf in embryo physiology

Embryo-derived paf (1-o-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is produced by de novo synthesis. This synthesis commences soon after fertilization and persists throughout the preimplantation phase. Paf is produced and released by the embryos of all mammalian species studied to date. Its release from the embryo involves binding to extracellular albumin in a manner that protects paf from enzymatic degradation. Released paf causes a range of alterations in maternal physiology, including platelet activation, changes in oviductal, endometrial and maternal immune function. Paf also acts in an autocrine fashion as a trophic/survival factor for the early embryo. In vitro, supplementation of culture media with paf improves embryo development. Embryo-derived paf's autocrine actions are transduced by 1-o-phosphatidylinositol-3-kinase, which induces characteristic calcium transients within the early embryo. The calcium transients require both the influx of external calcium and release of inositol trisphosphate-dependent internal calcium stores. Buffering these transients compromised embryo development in a manner that was reversed by exogenous paf. Assisted reproductive technologies compromise the production of paf by some embryos and retard the expression of the paf receptor. This deprivation of paf's action is one of the factors limiting the survivability of embryos produced by assisted reproductive technologies. Paf is one of several autocrine and paracrine trophic/survival factors that act on the early embryo. These factors probably act cooperatively and may, to some degree, be mutually redundant. As the earliest-released and the best-described embryotrophin, paf provides an important exemplar for understanding the role of ligand-mediated trophic support of the early embryo.

Embryonic production of nitric oxide and its role in implantation: a pilot study

PURPOSE

To investigate the ability of human embryos to produce nitric oxide (NO) and correlate its production with embryo quality and pregnancy rate.

METHODS

Twenty-three women participated in the study and were submitted to controlled ovarian stimulation and intracytoplasmic sperm injection. Embryos were singularly cultured in medium microdrops of 50 microL and were replaced, by transcervical transfer, at the 2- to 6-cell stage. In the culture media of each embryo the NO production was assessed by monitoring the levels of its stable oxidation products (nitrites/nitrates).

RESULTS

All the 23 patients underwent embryo transfer. After microinjection 64 embryos were obtained. The mean number of transferred embryos was 2.61 +/- 0.46 and the pregnancy rate was 26%. The mean nitrite/nitrate concentrations of culture medium of each embryo was significantly higher (5.88 +/- 2.34 micromol/L) than in pure P-1 medium (0.81 +/- 0.21 micromol/L; p < 0.001) demonstrating an embryonic secretion of NO. Comparing pregnant (7.34 +/- 2.72 micromol/L) versus nonpregnant patients (5.53 +/- 1.49 micromol/L; p = 0.022), the mean nitrite/nitrate concentrations were significantly higher. Furthermore, the best quality embryos of pregnant women produced significantly higher nitrite/nitrate concentrations than those of not pregnant patients.

CONCLUSIONS

It seems that NO production in nidating embryos is increased and that it may be primarily associated with a better morphology and a better growth potential of developing embryos.

Platelet-activating factor (PAF)-like activity, localization of PAF receptor (PAF-R) and PAF-acetylhydrolase (PAF-AH) activity in bovine endometrium at different stages of the estrous cycle and early pregnancy

PAF-like activity in the endometrium increased from days 2-4 to day 12 and day 20 in both cyclic and pregnant cows. There was an increase in platelet aggregation induced by PAF-like activity in the endometrium of pregnant animals on day 20 as compared to cyclic animals at the same point in time. Two major bands of PAF-R protein at 67 kDa and 97 kDa were detected by Western blot analysis. PAF-R was localized mainly in luminal and glandular epithelium of the endometrium, but the staining was markedly increased in the endometrium of pregnant cows on day 20 compared to cyclic animals on the same day. The purified PAF-AH from the endometrium is similar to in plasma. In cyclic cattle, no changes in PAF-AH activity of endometrium were observed, whereas a decrease in enzyme activity occurred in pregnant cows on day 20 as compared to cyclic animals on the same day. We suggest that the bovine endometrium produces PAF-like activity, expresses the PAF-R and possesses a PAF-AH activity which varies during pregnancy.

Antioestrogenic effect of trans-dehydrocrotonin, a nor-clerodane diterpene from Croton cajucara Benth. in rats

This study examined trans-dehydrocrotonin (t-DCTN), a nor-clerodane diterpene isolated from the Brazilian medicinal plant Croton cajucara Benth., for a possible antioestrogenic activity using immature rats as a model system for bioassay of oestrogen, and for an antiimplantation effect in regularly cycling rats of proven fertility. In the antioestrogen test, t-DCTN (25 and 50 mg/kg) effectively prevented oestrogen-induced increases of uterine wet weights. In addition, the vaginal openings provoked by oestrogen were completely prevented by t-DCTN. However, blastocyst-implantation was only insignificantly affected in t-DCTN pretreated animals. These results suggest that t-DCTN may be an antioestrogen and warrants further studies with regard to its mechanism of action.

A mannose-binding glycoprotein found in the 4 day post coital rat uterus is involved in pregnancy

Experiments were conducted to study the functional implication of a mannose-binding glycoprotein found in the day 4 post coital (p.c.) rat uterus, using a mono-specific polyclonal antibody raised against the glycoprotein. Western Blot and immunohistochemical techniques were employed to study the distribution of the glycoprotein, and the results suggest that this glycoprotein is present only in the day 4 p.c. uterus and is specifically localized in the stromal cells. Administration of anti-UA (Uterine Agglutinin) antiserum against the glycoprotein into the day 4 p.c. uterine lumen inhibits carrying of embryo to term. The antiserum is not embryo toxic. After in vivo in utero intra-luminal administration of anti-UA antiserum in day 4 p.c. rat the antiserum has been specifically localized in the uterine stroma by immunohistochemistry. After intravenous injection, the glycoprotein is cleared mainly through the kidney and liver. The possible role of this glycoprotein in the implantation process in rats has been discussed. From the data it is evident that UA may not be directly involved in sugar-sugar interactions with embryo since it is not present in any significant amount in pregnant uterus from day 5 onwards. Since other experiments show that UA does have some role to play in early pregnancy, UA probably acts through some other factor, and preliminary studies suggest that this factor maybe TGF-beta3.

Ontogeny of expression of a receptor for platelet-activating factor in mouse preimplantation embryos and the effects of fertilization and culture in vitro on its expression

Platelet-activating factor (PAF; 1-o-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a potent ether phospholipid. It is one of the preimplantation embryo's autocrine growth/survival factors. It may act via a G protein-linked receptor on the embryo; however, the evidence for this is conflicting. The recent description of the intracellular form of the PAF:acetlyhydrolase enzyme as having structural homology with G proteins and Ras also suggests this as a potential intracellular receptor/transducer for PAF. This study used reverse transcription-polymerase chain reaction to examine the ontogeny of expression of the genes for these proteins in the oocyte and preimplantation-stage embryo. Transcripts for the G protein-linked PAF receptor were detected in the late 2-cell-stage embryo and in all stages from the 4-cell stage to blastocysts. They were also present in unfertilized oocytes and newly fertilized zygotes but only at relatively low levels. The incidence of expression was generally low and variable in late zygotes and early 2-cell embryos. Expression past the 2-cell stage was alpha-amanitin sensitive. The results indicated that mRNA for this receptor is a maternal transcript that was degraded during the zygote-2-cell stage. New expression of the receptor transcript required activation of the zygotic genome. Fertilization of embryos in vitro caused this transcript not to be expressed in the zygote. Culture of zygotes (irrespective of their method of fertilization) caused expression from the zygotic genome to be retarded by more than 24 h. This retardation did not occur if culture commenced at the 2-cell stage. The transcripts for the subunits of intracellular PAF:acetylhydrolase were not detected in oocytes or at any stage of embryo development examined, despite their being readily detected in control tissue. This study confirms the presence of the G protein-linked PAF receptor in the 2-cell embryo and describes for the first time its normal pattern of expression during early development. The adverse effects of in vitro fertilization (IVF) and embryo culture on the expression of this transcript may be a contributing factor for the poor viability of embryos produced in this manner. The reduced expression of PAF-receptor mRNA following IVF predicts that such embryos may have a deficiency in autocrine stimulation and also suggests that supplementation of growth media with exogenous PAF would be only partially beneficial. The effect of IVF and culture may also explain the conflicting literature.

Interaction between uterine PGE and PGF2 alpha production and the nitridergic system during embryonic implantation in the rat

Embryonic implantation is a complex process in which both maternal and embryonic signals are involved. In the present study, we evaluated changes in uterine prostaglandins production and nitric oxide synthase (NOS) activity during the course of early pregnancy and their interaction during implantation in rats. Uterine phospholipase A2 (PLA2) activity is increased on days 5 (day of ovoimplantation) and 6, compared to preimplantation days (3 and 4). This enhanced activity might be responsible for the observed increase in uterine PGE and PGF2 alpha production observed on day 5 of pregnancy, which induces endometrial vascular permeability and decidualization. When embryo access to the uterus is impaired, the increase of PG production is suppressed. During postimplantation, PGE levels return to preimplantation values, while PGF2 alpha decreased with respect to preimplantation values. Uterine NOS activity is also increased on day 4 and reaches a maximum on day 5, with a profile similar to PGE and PGF2 alpha. Dexamethasone administered in vivo decreased uterine NOS activity on day 4 of pregnancy but not on day 5, suggesting the presence of at least two types of NOS enzymes in the early days of pregnancy. A competitive inhibitor of NOS, L-NAME (600 and 1000 microM) induced a decrease in PGE and PGF2 alpha production in uterine tissue on day 5 of pregnancy. These results suggest the existence of a physiologically relevant nitridergic system which modulates prostaglandin production in the rat uterus during embryonic implantation.

Effects of platelet activating factor on mouse embryo implantation in vitro

PURPOSE

Our purpose was to assess the role of platelet activating factor (PAF) in embryo implantation, we examined the effects of PAF and a PAF antagonist on the in vitro implantation of mouse embryos, using an in vitro embryo culture system in the absence of the endometrium.

METHODS

BDF1 mouse pronuclear-stage embryos were cultured until they developed to the two-cell, the four- to eight-cell, or the morula stage in the absence of PAF or its antagonist CV6209. The medium was then changed and supplemented with PAF or CV6209 at various concentrations. We also examined the reversible effects of PAF addition to the media containing the PAF antagonist.

RESULTS

The addition of PAF to the culture from the two-cell stage significantly (P < 0.05) increased the rates of embryo implantation in vitro (control, 69.8%; 10(-10) M PAF, 90.1%; 10(-9) M PAF, 95.5%). Similarly, the addition of PAF to the cultures from the four- to eight-cell and morula stage also significantly (P < 0.05) increased their rates of implantation in vitro. In contrast, the addition of CV6209 to the culture significantly (P < 0.01) decreased the rates of embryo implantation in vitro. CV6209 also decreased the rate of blastocyst formation. The degree of inhibition by CV6209 decreased with the advancing stage of embryos. The addition of PAF to media containing CV6209 reversed the inhibition and restored the implantation rate in vitro.

CONCLUSIONS

These results suggest that PAF may act directly on the mouse embryo and favor its implantation like an autocrine activating factor, irrespective of the presence or absence of the endometrium.

The effect of platelet activating factor antagonist (BN 52021) on pregnancy duration and collagen content in the pregnant rat uterus and cervix

In order to study the role of Platelet Activating Factor (PAF) in the mechanism of parturition and connective tissue metabolism in the pregnant rat uterus, we investigated the influence of the Platelet Activating Factor Receptor Antagonist (BN 52021) on gestation duration and collagen concentration in pregnant rat uterus and cervix at term. Total and soluble collagen as well as dry tissue/wet tissue ratio were measured in the BN 52021 treated group (n = 9) and in the control group (n = 13). Gestation duration was evaluated in a group receiving BN 52021 (n = 10) and in a control group (n = 19) receiving pure solvent. There were no significant differences in water content. The total and soluble collagen concentration was also similar to the control in both the uterus and the cervix. The only significant difference was observed in the soluble collagen/total collagen ratio in the uterus. BN 52021 administration did not alter the gestational period. Basing on this experiment we suggest that not all the phospholipid metabolites activated by phospholipase A2 significantly influence the duration of pregnancy and connective tissue metabolism in the pregnant rat uterus.

Platelet-activating factor induces collagenase expression in corneal epithelial cells

Platelet-activating factor (PAF), a potent lipid mediator involved in inflammatory and immune responses, accumulates rapidly in response to injury in a variety of tissues, including the corneal epithelium. However, the precise role of this compound in the cascade of events following insult has not been defined. Here we examined the effect of PAF on gene expression in the epithelial cells of rabbit corneas in organ culture. We found that incubation with 100 nM methylcarbamoyl PAF, a nonhydrolyzable analog of PAF, produced rapid transient 2.8- and 3.5-fold increases in the expression of c-fos and c-jun, respectively, at 1 hr, followed by increased expression of the collagenase type I gene beginning at 3 hr and peaking at 14-fold by 8 hr. Addition of the protein-synthesis-inhibitor cycloheximide superinduced c-fos and c-jun, strongly potentiating the PAF effect, but inhibited the induction of collagenase type I expression, suggesting the existence of a transcriptional factor linking the two events. BN-50730, a selective antagonist of intracellular PAF-binding sites, blocked the expression of the immediate-early genes as well as the increase in collagenase type I mRNA. Our results suggest that one of the functions of PAF may be to enhance the breakdown of the extracellular matrix as a part of the remodeling process during corneal wound healing after injury. Pathologically, a PAF-induced overproduction of collagenase may be a factor in the development of corneal ulcers, as well as other pathophysiological conditions such as cartilage destruction in arthritis. If so, inhibitors of this signal-transduction pathway may be useful as tools for further investigation and, eventually, as therapeutic agents to treat such disorders.

The effects of platelet-activating factor on the output of prostaglandins from the guinea-pig uterus

Platelet-activating factor (PAF) significantly increased the output of prostaglandin (PG) F2 alpha from the guinea-pig uterus during the mid-cycle phase (Days 6-10), but only had a small, non-significant stimulatory effect on the outputs of PGE2 and 6-keto-PGF1 alpha. PAF significantly increased the outputs of PGF2 alpha, PGE2 and 6-keto-PGF1 alpha from the guinea-pig uterus during the later phase of the cycle (Days 15-17). Lack of extracellular calcium did not affect the stimulatory effect of PAF on uterine PG output. However, TMB-8 (an intracellular calcium antagonist) prevented the increases in uterine PG output produced by PAF at both phases of the cycle. These results suggest that the stimulatory effect of PAF on uterine PG output in the guinea-pig is dependent upon the mobilization of intracellular calcium but is not dependent upon the uptake of extracellular calcium. Also, the weak stimulatory effect of PAF on PGE2 output from the uterus during the mid-cycle phase indicates that, if PAF is involved in implantation in guinea-pigs, it probably does not act via PGE2. Also, the lack of an inhibitory effect of PAF on uterine PGF2 alpha synthesis and release suggests that PAF is not the anti-luteolytic factor produced by the guinea-pig conceptus during early pregnancy.

Platelet-activating factor levels in human follicular and amniotic fluids

Platelet-activating factor (PAF) was estimated in extracts of human follicular and amniotic fluids using a commercially available 125I-radioimmunoassay. Levels obtained before and after purification of the extracts by thin-layer chromatography were similar and PAF could be estimated with high accuracy and reproducibility over a wide dilution range. PAF levels in fluid aspirated from mature (17 mm average diameter) follicles from in vitro fertilization patients were 1005 +/- 129 fmol/ml in successful (clinical pregnancy) cycles and 949 +/- 75 fmol/ml in unsuccessful (failure of implantation) cycles. PAF levels were also similar in follicles containing eggs and those where no egg was found, and in fluid from follicular cysts characterised by low oestradiol and progesterone levels. PAF was detected in midtrimester amniotic fluid (60 +/- 20 fmol/ml). At term, PAF was low or undetectable in amniotic fluid obtained at elective caesarean section before the onset of labour, but increased to 102 +/- 28 fmol/ml in samples obtained following spontaneous labour and vaginal delivery. The data suggest that PAF may be involved in ovulation and parturition but further studies into the mechanism of action of PAF are necessary. The good performance of the radioimmunoassay and the convenience of gamma-counting are strong advantages of this method over the available bioassays, but its expense remains a drawback.

The effect of platelet activating factor on ovulation

The mechanism of ovulation has been compared to an inflammatory reaction. Platelet activating factor (PAF) is an important mediator of inflammation as it may induce the production of prostaglandins and lysosomal enzyme. We evaluated the potential role of PAF in PMSG-HCG induced ovulation using CV3988, a specific PAF receptor antagonist in a superovulated ICR mice (9-12 weeks old). CV3988 blocked the ovulation in a dose dependent manner, and the significant reduced ovulatory efficiency was observed at more than 500 micrograms dose (p less than 0.001). The ovulatory efficiency reduced by CV3988 was reversed by PAF in a dose dependent manner. In vitro fertilization (IVF) rate of follicular oocytes with treatment of CV3988 was not different from that of ovulated ova without treatment. These results suggest that PAF may be involved in the ovulation process but the presence of PAF may not be essential for the fertilization of the ova as IVF.

Autoradiographic localization of platelet-activating factor (PAF) binding sites in the rabbit endometrium during the peri-implantation period

This communication describes the use of in-vivo and in-vitro autoradiography to map specific platelet-activating factor (PAF) receptors in the rabbit uterus. Specific [3H]PAF uptake was predominantly localized on epithelial, but not on stromal or myometrial cells. Very few silver grains were associated with the luminal epithelial cells in the uterus of the estrous rabbit, primarily because of the non-differentiated state of the epithelium. In the differentiated pregnant uterus, significantly more [3H]PAF was bound to the glandular epithelial cells, with the stromal cells binding consistently significantly less. The highest density of silver grains was observed at the implantation sites on day 7 of pregnancy. There was no apparent difference in [3H]PAF C18:0 uptake between the epithelial cells at the inter-implantation zone on day 7 and on day 6. Bound [3H]PAF was displaceable by lyso-PAF, U66985, CV3988, but not U66982, L652,731, SRI 63,441 or the inactive PAF isomer, oleoyl PAF. Bovine serum albumin (BSA) significantly inhibited tissue uptake of [3H]PAF C18:0. Intraluminally administered [3H]PAF C18:0 and intravenously injected [3H]methylcarbamyl-PAF, a non-metabolizable PAF analog, penetrated the implanted blastocyst and bound to the embryoblast. This event was reproducible in vitro with pre-implantation blastocysts from day-6 pregnant rabbits, which suggests that uterine-derived PAF may translocate into the blastocyst after attachment.

Platelet-activating factor-acether is a component of human follicular fluid

OBJECTIVE

Platelet-activating factor-acether (PAF-acether) presence was investigated in 27 human follicular fluids (FFs).

DESIGN

Aggregation of washed rabbit platelets was used to measure PAF-acether. Data were compared using Student's t-test.

SETTING

Follicular fluids came from the in vitro fertilization program at Antoine Béclère Hospital, and PAF-acether was assayed at Institut National de la Santé et de la Recherche Médicale, Unités 187 and 200, Clamart, France.

PATIENTS, PARTICIPANTS

The study concerned five infertile women 29 to 39 years of age.

INTERVENTIONS

Ovaries were stimulated with human menopausal gonadotropin under gonadotropin-releasing hormone agonist (GnRH-a) action.

MAIN OUTCOME MEASURES

The height of platelet aggregation was compared between FFs and synthetic PAF-acether.

RESULTS

Mean FF concentration of PAF-acether was 1,367 to 3,467 pg/mL among women. Values were higher for patients in a long than in a short GnRH-a protocol (P less than 0.05). However, PAF-acether concentration was not related to fertilization rate.

CONCLUSIONS

Platelet-activating factor-acether is possibly involved in oocyte release from the follicle, a process occulted by follicular puncture.

A consideration of the factors which influence and control the viability and developmental potential of the preimplantation embryo

The advent of the new reproductive technologies (including in vitro fertilization) has led to a revolution in the treatment of infertility. It has not yet led to a marked improvement in our understanding of the control of development and of viability of the early embryo. It is the poor viability of embryos, with consequent implantation failure, which is the major limiting factor to successful outcomes. While much of the research in this area has concentrated on strategies of ovulation induction, experimental models have shown that the major cause of reduced embryo viability is due to the actual process of fertilization in vitro and subsequent culture of the preembryo in synthetic culture medium. It is likely that this is due to the absence of critical nutrients or trophic factors of maternal origin and work with co-culture of embryos with somatic cells suggests improved viability can be achieved. Such co-culture is not an option for routine clinical use, however. It is essential therefore to understand by detailed study of the physiology of embryonic development their requirements for optimal development. The empirical approach of comparing different formulations of culture media is unlikely to be successful because of the vast range of parameters to be tested and the large number of pregnancies required to demonstrate a significant improvement in outcome. The strategy that is most likely to be successful in the future, therefore, is the use of appropriate experimental models, such as the developing rodent embryo, to understand the essential physiological changes in the embryo during its development, the control processes in place, and the effect of the embryo's environment on the processes. This will allow the rational design of culture media which can then be rigorously tested for improved outcome. An example of successful application of this approach is the discovery of embryo-derived platelet activating factor (PAF). The production of embryo-derived PAF was first described and validated in the rodent. In the same species it was shown to have an essential role in pregnancy and to act as an autocrine mediator of embryo viability. This fundamental observation in rodents was then confirmed in humans, and recent work has shown that supplementation of culture human embryo media with PAF results in a dramatic increase in their developmental and pregnancy potential. This example should be the first of many such improvements based on a more fundamental understanding of the embryo's developmental requirements.

Embryo-derived platelet activating factor, a marker of embryo quality and viability following ovarian stimulation for in vitro fertilization

Embryo-derived platelet-activating factor (PAF) may be an important mediator of early maternal recognition of pregnancy. PAF was higher in media associated with clinical pregnancies when compared to preclinical pregnancies but not higher in pregnant vs nonpregnant groups. The production of PAF by the preimplantation embryo was not related to follicle size or embryo morphology. However, differences in PAF concentrations in the culture media were related to the age of the embryo culture medium and the developmental stage of the embryo.

Blood constituents during the estrous cycle and early pregnancy in dairy cows

The objective of this study was to determine if maternal platelet count, white blood cell count or other blood constituents undergo sustained alterations in concentration following fertilization. Blood samples from 17 Holstein females were collected over an 18-d period starting at estrus. Blood was analyzed for levels of platelets, white blood cells, red blood cells, hemoglobin and hematocrit. Results were analyzed for differences between nonpregnant and pregnant groups. Analysis of variance revealed a day-by-group interaction in the platelet count (P<0.01). White blood cell count showed both a day-by-group interaction and a difference between days (P<0.01). Red blood cell count, hematocrit and hemoglobin levels resulted in no significant difference between the two groups (P>0.05). While statistically significant differences were observed in platelet and white blood cell count, neither of these were sustained over a period longer than 2 d.

Pregnancy suppression by a structurally related antagonist for platelet activating factor, CV-6209, in mice

The effects of CV-6209, a structurally related antagonist for platelet activating factor (PAF), on pregnancy were investigated in mice, so that the physiologic significance of PAF production by and secretion from preimplantation embryos could be elucidated. When it was repeatedly administered to pregnant mice during days 1-6 of pregnancy, CV-6209 prevented preimplantation thrombocytopenia and reduced the number of implantation sites dose-dependently, CV-6209 suppression of pregnancy was eliminated by concomitant administrations of PAF. When it was administered on various fractional days of pregnancy, CV-6209 suppressed pregnancy most effectively in mice treated during days 4-5 of pregnancy, the days of implantation. CV-6209 treatment exhibited no apparent effect on embryonic development. Implantation was suppressed when day 4 embryos from saline-treated donor mice were transferred in utero to CV-6209-treated recipient mice. Once implanted, however, their in utero growth was normal. The results indicate that PAF is prerequisite to pregnancy by promoting embryonic implantation.

A novel enhancing effect of platelet activating factor (PAF) on glucose oxidation in uteri from pregnant rats. Participation of prostaglandins and leukotrienes

The effects of platelet activating factor (PAF) on glucose oxidation in uterine strips isolated from rats in the 4 th and 5 th day of pregnancy, were explored. PAF, at a concentration of 10(-10) and 10(-8) M, augmented significantly the generation of 14CO2 from labelled glucose in uteri from pregnant rats in the 4 th day of pregnancy. When the tissue was obtained from 5 days pregnant rats, the addition of PAF at 10(-8) increased significantly more than PAF at 10(-10) M the metabolism of glucose. On the other hand, PAF at 10(-8) M failed to alter the uterine basal production of 14CO2 from labelled glucose in animals at estrus. BN52021, a specific PAF antagonist employed at 10(-5) M, blocked completely the action of PAF in the pregnant rat uterus. PGE1, PGE2 and PGF2 alpha enhanced significantly the formation of 14CO2 from labelled glucose in uteri from 5 days pregnant rats. Indomethacin, a well known inhibitor of prostaglandin synthesis, did not alter the basal glucose metabolism in uteri from 5 days pregnant rats, but antagonized completely the stimulating action of PAF on 14CO2 production from labelled glucose an effect that was partially reverted by the addition of PGE1, PGE2 or PGF2 alpha (10(-7) M). Furthermore, nordihydroguaiaretic acid (NDHGA), a specific inhibitor of 5-lipoxygenase at 10(-5) M, as well as FPL-55712, an antagonist of leukotrienes (LTs), at the same concentration, blocked the action of PAF on the metabolism of glucose. The action of NDHGA was partially counteracted by the addition of LTC4 at 10(-7) M.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of spermatozoal platelet-activating factor in fertilization

Platelet-activating factor (PAF), a potent lipid mediator of inflammation, has been shown to play a role in both the implantation and viability of mammalian embryos. We examined whether human and mouse spermatozoa release PAF during in vitro incubation and assessed the effect of exogenous PAF and the PAF receptor antagonist WEB 2086, a thieno-triazolodiazepine, on mouse in vitro fertilization (IVF) rate. PAF biological activity was detected in 11 samples of leukocyte-free, purified human spermatozoa (28 pg PAF/10(6) cells/24 hr) and 5 samples of epididymal mouse spermatozoa (7.8 pg PAF/10(6) cells/3 hr). Exogenous PAF (10(-8) and 10(-6) M) increased (p less than 0.01) the fertilization rate 2- and 3-fold, respectively of mouse oocytes by mouse epididymal spermatozoa. 10(-4) M PAF, however, reduced sperm motility and decreased (p less than 0.05) the fertilization rate. 10(-6) M WEB 2086, decreased IVF to approximately 50% of the control fertilization rate (42% vs. 89%). WEB 2086 treatment also promoted the attachment of supernumerary spermatozoa to both fertilized and unfertilized oocytes. The fertilization rate in the presence of WEB 2086 returned to control levels when zona-pellucida-free oocytes were employed, indicating that WEB 2086 did not interfere with the spermatozoal acrosome reaction. These data suggest that PAF, of spermatozoal origin, may be important in mammalian fertilization.

Effects of platelet activating factor on mouse oocyte fertilization in vitro

Platelet activating factor is rapidly gaining acceptance as a potent mediator in many reproductive processes. This study presents data that indicate a direct role of platelet activating factor in fertilization. Platelet activating factor was shown to significantly increase (p less than 0.001) the fertilization rate of mouse oocytes in vitro. Furthermore, CV3988, an inhibitor of platelet activating factor, was noted to significantly decrease in vitro fertilization rates at 10(-5) and 10(-4) mol/L concentrations.

Supplementation of in-vitro fertilisation culture medium with platelet activating factor

The supplementation of culture medium with platelet activating factor (PAF) on the subsequent implantation and pregnancy potential of pre-embryos produced by in-vitro fertilisation was studied. Pre-embryo culture medium was supplemented with 0 (control), 0.186, 0.93, or 1.49 mumol/1 PAF. Pre-embryos were transferred to PAF-containing medium 15-17 h after insemination (ie, just before syngamy) for 24 h and then transferred to the uterus. For 185 women receiving control pre-embryos, the pregnancy rate (positive beta human chorionic gonadotropin per oocyte retrieval) was 10.2%, while 166 women who received PAF treated pre-embryos (all concentrations combined) achieved a pregnancy rate of 17.5%. This difference was significant. The pregnancy rates per pre-embryo transferred were 6.1% and 9.4% for the control and PAF groups, respectively. The percentage of positive pregnancy tests that resulted in a viable pregnancy (presence of fetal heart at 8 weeks) was 78.9% in the controls and 75.9% in the PAF group. There was no difference in the average number of embryos transferred in either group. The increase in the pregnancy rate after a short exposure of pre-embryos to PAF in vitro suggests that PAF mediates pre-embryo development.

Levels of interleukin-2 receptor in serum of patients during the menstrual cycle and following embryo/gamete transfer

In an attempt to establish whether nidation elicits a measureable systemic immunologic response in vivo, levels of interleukin-2 receptor (IL-2R) have been determined in serum drawn from 34 pregnant patients (IUP) immediately before embryo/gamete transfer, and 7 and 14 days later. For comparison, these same values were determined for 41 subjects who did not conceive, and for 18 who spontaneously aborted (SAB) during the first trimester of gestation. Serum IL-2R values were near 320 U/ml and did not differ between days within outcomes, or within days between outcomes. Furthermore, levels of IL-2R and beta-hCG in serum were not interrelated on days 7 or 14 of pregnancy (SAB or IUP). Serum IL-2R levels did not change during the menstrual cycle. The present results appear to traverse presumptive elements of existing hypotheses of "placental immunotropism."

The involvement of platelet activating factor in ovulation

Follicle rupture during ovulation is associated with inflammation-like changes. Because platelet activating factor (PAF) participates in the inflammatory process, the effect of a PAF-specific antagonist, BN52021, on the ovulatory response was tested in rats. BN52021, administered locally, inhibited follicle rupture in rats stimulated to ovulate with human chorionic gonadotropin (hCG). In addition to suppressing rupture of the follicles, this antagonist suppressed the hCG-stimulated increase in ovarian collagenolysis and vascular permeability. The inhibition of ovulation of BN52021 could be reversed by simultaneous administration of PAF. Furthermore, PAF partially reversed the blockage of ovulation by inhibitors of eicosanoid synthesis. Collectively, these results suggest the involvement of PAF in ovulation. Its role seems to be closely related to the metabolism of arachidonic acid. Thus, modulation of PAF action may serve as an additional target for regulation of reproduction via its action on ovulation.

Evidence that the establishment of pregnancy requires activation of lipoxygenase and phospholipase-A2

The present work investigates the possibility that lipoxygenase products are involved in the biochemical mechanisms of blastocyst implantation by utilizing nordihydroguaiaretic acid (NDGA) and caffeic acid (CA), inhibitors of lipoxygenase enzymes, and quinacrine (QU), an inhibitor of phospholipase-A2. It has been shown previously that inhibition of cyclooxygenase results in blockade of implantation. The inhibitors were dissolved in a standard medium and 5 microliter of the solutions were micro-injected into the uterine horns of day-4 pregnant mice. The contralateral horns acted as controls and received only vehicle. A sham-operated group provided normal controls. In 14 NDGA-treated mice, the control horns contained 40 implantations while the treated horns contained only 6 small implantations and 8 resorbing sites. These control horns were comparable to the sham controls. In 14 CA-treated mice, treated horns contained 17 small implantations plus 4 resorptions, whereas the control horns contained 26 small implantations and 4 resorptions. Twelve QU-treated mice exhibited 7 small implantations and 4 resorptions in the treated horns, plus 24 small sites and no resorptions in the control horns. Fourteen sham-operated mice had 95 implantation sites and no resorptions in their 28 horns. The results provide evidence for the involvement of the lipoxygenase enzymes and phospholipase-A2 in the initial implantation process and in the subsequent development of early pregnancy.