Placental Protein Synthesis Research Articles

Maternal L-proline supplementation enhances fetal survival, placental development, and nutrient transport in mice†.

L-Proline (proline) in amniotic fluid was markedly increased during pregnancy in both pigs and sheep. However, in vivo data to support a beneficial effect of proline on fetal survival are not available. In this study, pregnant C57BL/6J mice were fed a purified diet supplemented with or without 0.50% proline from embryonic day 0.5 (E0.5) to E12.5 or term. Results indicated that dietary supplementation with proline to gestating mice enhanced fetal survival, reproductive performance, the concentrations of proline, arginine, aspartic acid, and tryptophan in plasma and amniotic fluid, while decreasing the concentrations of ammonia and urea in plasma and amniotic fluid. Placental mRNA levels for amino acid transporters, including Slc36a4, Slc38a2, Slc38a4, Slc6a14, and Na+/K+ ATPase subunit-1α (Atp1a1), fatty acid transporter Slc27a4, and glucose transporters Slc2a1 and Slc2a3, were augmented in proline-supplemented mice, compared with the control group. Histological analysis showed that proline supplementation enhanced labyrinth zone in the placenta of mice at E12.5, mRNA levels for Vegf, Vegfr, Nos2, and Nos3, compared with the controls. Western blot analysis showed that proline supplementation increased protein abundances of phosphorylated (p)-mTORC1, p-ribosomal protein S6 kinase (p70S6K), and p-eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), as well as the protein level of GCN2 (a negative regulator of mTORC1 signaling). Collectively, our results indicate a novel functional role of proline in improving placental development and fetal survival by enhancing placental nutrient transport, angiogenesis, and protein synthesis.

Dietary leucine supplementation minimises tumour-induced damage in placental tissues of pregnant, tumour-bearing rats.

BackgroundThe occurrence of cancer during pregnancy merges two complex, poorly understood metabolic and hormonal conditions. This association can exacerbate the conditions of both the mother and the foetus. The branched-chain amino acid leucine enhances cellular activity, particularly by increasing protein synthesis. This study aimed to analyse the modulatory effect of a leucine-rich diet on direct and indirect tumour-induced placental damage. This was accomplished by evaluating the expression of genes involved in protein synthesis and degradation and assessing anti-oxidant enzyme activity in placental tissues collected from pregnant, tumour-bearing rats.ResultsPregnant rats were either implanted with Walker 256 tumour cells or injected with ascitic fluid (to study the indirect effects of tumour growth) and then fed a leucine-rich diet. Animals in a control group underwent the same procedures but were fed a normal diet. On the 20th day of pregnancy, tumour growth was observed. Dams fed a normoprotein diet showed the greatest tumour growth. Injection with ascitic fluid mimicked the effects of tumour growth. Decreased placental protein synthesis and increased protein degradation were observed in both the tumour-bearing and the ascitic fluid-injected groups that were fed a normoprotein diet. These effects resulted in low placental DNA and protein content and high lipid peroxidation (measured by malondialdehyde content). Decreased placental protein synthesis-related gene expression was observed in the tumour group concomitant with increased expression of genes encoding protein degradation-associated proteins and proteolytic subunits.ConclusionsConsumption of a leucine-rich diet counteracted the effects produced by tumour growth and injection with ascitic fluid. The diet enhanced cell signalling, ameliorated deficiencies in DNA and protein content, and balanced protein synthesis and degradation processes in the placenta. The improvements in cell signalling included changes in the mTOR/eIF pathway. In conclusion, consumption of a leucine-rich diet improved placental metabolism and cell signalling in tumour-bearing rats, and these changes reduced the deleterious effects caused by tumour growth.

The endocannabinoid 2-arachidonoylglycerol dysregulates the synthesis of proteins by the human syncytiotrophoblast

In recent years, endocannabinoids emerged as new players in various reproductive events. Recently, we demonstrated the involvement of 2-arachidonoylglycerol (2-AG) in human cytotrophoblast apoptosis and syncytialization. However, 2-AG impact in hormone production by the syncytiotrophoblast (hST) was never studied. In this work, we demonstrate that 2-AG activates cannabinoid (CB) receptors, exerting an inhibitory action on cyclic AMP/protein kinase A (cAMP/PKA) and mitogen-activated protein kinase (MAPK) p38 pathways, and enhancing ERK 1/2 phosphorylation. Furthermore, 2-AG affects the synthesis of human chorionic gonadotropin (hCG), leptin, aromatase, 3-β-hydroxysteroid dehydrogenase (3-β-HSD), and placental protein 13 (PP13). These 2-AG effects are mediated by the activation of CB receptors, in a mechanism that may involve p38, ERK 1/2 and cAMP/PKA pathways, which participate in the regulation of placental proteins expression.To our knowledge, this is the first study that associates the endocannabinoid signalling and endocrine placental function, shedding light on a role for 2-AG in the complex network of molecules that orchestrate the production of placental proteins essential for the gestational success.

Intrauterine growth restriction (IUGR) is associated with increased leptin synthesis and binding capability in neonates

Animal studies suggest pathological foetal programming of hypothalamic circuits regulating food intake in the setting of leptin deficiency and intrauterine growth restriction (IUGR). We aimed to compare placental leptin synthesis and leptin-binding capability in venous cord blood between IUGR newborns and neonates born appropriate for gestational age (AGA). Prospective controlled multicentre study. Twenty-one ultrasound-proven IUGR and 33 AGA neonates. The concentration of leptin and soluble leptin receptor (sOB-R) in venous cord blood at birth was determined. Moreover, placental gene and protein expression of leptin and placental mRNA expression of functional and total leptin receptor isoforms were measured. Whereas log-leptin concentration in venous cord blood did not differ between IUGR and AGA newborns, the concentration of log-sOB-R was elevated in IUGR neonates (p(confounder adjusted)=0·009). Placental leptin protein synthesis as well as leptin mRNA was significantly higher in IUGR than in AGA infants (log-transformed, relative gene expression, p(confounder adjusted)=0·004). Analysis of gene expression of functional and total leptin receptor isoforms did not show any difference between both groups. Leptin-binding capability in venous cord blood is increased in IUGR newborns. Thus, via foetal programming, reduced biologically active leptin levels might contribute to a perturbed regulation of appetite.

Placental production and maternal serum and urine levels of inhibin A and activin A are modified by antihypertensive therapy in hypertensive disorders of pregnancy

Levels of inhibin A and activin A are raised in pre-eclampsia (PE) but it is not known if antihypertensive therapy can affect their levels. Our aim was to investigate the effect of the antihypertensive drug alpha-methyldopa on serum, urine and placental concentrations of inhibin A and activin A in women presenting with hypertensive disorders of pregnancy. This was a cross-sectional study. We recruited 65 women presenting with PE, 39 with gestational hypertension (GH) and 104 normotensive controls matched for maternal age, gestational age and parity. Using specific validated ELISAs, serum and urine levels of inhibin A and activin A, and uterine artery Doppler indices, were measured before and 24-48 h after initiating alpha-methyldopa therapy in women with PE, with GH and controls. Protein extracts were obtained from samples of placental tissue from another group of women with PE, GH and controls for the same analysis. In PE, but not GH, alpha-methyldopa therapy was associated with significantly (P < 0.05) lower levels of both serum and urine inhibin A and activin A. Similarly, in PE but not GH, alpha-methyldopa therapy was associated with lower placental levels of both markers (P < 0.05). There was no significant difference in pulsatility index following treatment in either PE or GH. Our data indicate that antihypertensive therapy with alpha-methyldopa may have an effect on the synthesis and/or release of placental proteins in pregnancies complicated by PE and that this effect may be independent of its known antihypertensive action.

Evidence of Placental Translation Inhibition and Endoplasmic Reticulum Stress in the Etiology of Human Intrauterine Growth Restriction

Unexplained intrauterine growth restriction of the fetus (IUGR) results from impaired placental development, frequently associated with maternal malperfusion. Some cases are complicated further by preeclampsia (PE+IUGR). Here, we provide the first evidence that placental protein synthesis inhibition and endoplasmic reticulum (ER) stress play key roles in IUGR pathophysiology. Increased phosphorylation of eukaryotic initiation factor 2alpha suggests suppression of translation initiation in IUGR placentas, with a further increase in PE+IUGR cases. Consequently, AKT levels were reduced at the protein, but not mRNA, level. Additionally, levels of other proteins in the AKT-mammalian target of rapamycin pathway were decreased, and there was associated dephosphorylation of 4E-binding protein 1 and activation of glycogen synthase kinase 3beta. Cyclin D1 and the eukaryotic initiation factor 2B epsilon subunit were also down-regulated, providing additional evidence for this placental phenotype. The central role of AKT signaling in placental growth regulation was confirmed in Akt1 null mice, which display IUGR. In addition, we demonstrated ultrastructural and molecular evidence of ER stress in human IUGR and PE+IUGR placentas, providing a potential mechanism for eukaryotic initiation factor 2alpha phosphorylation. In confirmation, induction of low-grade ER stress in trophoblast-like cell lines reduced cellular proliferation. PE+IUGR placentas showed elevated ER stress with the additional expression of the pro-apoptotic protein C/EBP-homologous protein/growth arrest and DNA damage 153. These findings may account for the increased microparticulate placental debris in the maternal circulation of these cases, leading to endothelial cell activation and impairing placental development.

Relationships between TGFbeta proteins and oxygen concentrations inside the first trimester human gestational sac.

In early pregnancy, the O2 gradient between the maternal circulation and the gestational sac tissues modulates trophoblast biological functions. The aim was to evaluate if placental partial pressure of oxygen (PaO2) modulates in vivo synthesis of specific placental proteins inside the first trimester gestational sac. Matched samples of peripheral venous blood, blood from the placental bed (PB), coelomic fluid (CF) and placental tissue were obtained in 37 normal pregnancies at 6–12 weeks gestation. PaO2 was measured in PB and CF using an IRMA blood gas monitor. Inhibin A, activin A, sEng, PlGF, sFlt-1 and free VEGF concentrations were measured in all samples. HSP 70 was measured in placental extracts. ANOVA showed ∼60% increase in PB PaO2 (P = 0.02) between after 10 weeks gestation. Unpaired Student's T-test between two groups (6–9 weeks vs 9–12 weeks) shows a significant increase in MS Activin A (P = 0.001), CF activin A (P<0.001), MS P1GF (P = 0.001), CF PlGF (P<0.001), MS sFLT-1 (P = 0.03), CF sFLT-1 (P = 0.01), HSP 70 in placental extracts (P = 0.04) and a significant decrease in PB inhibin A levels (P<0.001) and PB sFLT-1 (P = 0.02) . Multiple correlation analysis showed a significant negative correlation between PB inhibin A levels and gestation (r = −0.45, P<0.05) and PB PaO2 (r = −0.5, P = 0.008) and also between sFLT-1 and PB PaO2 (P = 0.03). There was a positive correlation (P<0.01) between PlGF, sEng and VEGF levels in the placental extracts. Our results indicate a direct relationship in the early intrauterine PaO2 in vivo and inhibin A and sFLT-1 concentrations confirming our hypothesis that specific placental proteins are regulated by intrauterine O2 tension.

Differential effects of protein malnutrition in pregnant rats on the expression of placental prolactin-like proteins

Summary This study evaluated the effect of chronic protein deficiency during pregnancy on the synthesis of placental lactogen (PL) and prolactin-like proteins (PLPs). Pregnant rats were pair-fed isocaloric diets containing 20% (C) or 5% casein (low protein, LP). In LP animals, maternal weight gain was significantly decreased by 82%, fetal body weight by 20% and placental weight by 30%. These data confirm that this low protein adequate calorie diet results in significant feto-placental growth retardation. Maternal plasma levels of growth hormone (GH), insulin-like growth factor 1 (IGF-1) and thyroid stimulating hormone (TSH) did not significantly differ between C and LP dams, whereas IGF-1 in maternal kidney tissue was significantly higher in LP than in C animals. Placental tissue explants cultured in the presence of [ 35 S]-labeled methionine showed that total secretion of de novo synthesized protein did not differ between C and LP explants. Analysis of secreted proteins by polyacrylamide gel electrophoresis and Western immunoblot procedures revealed that the level of PLP-B immunoreactive protein was significantly decreased by 45% in media from LP placentae, whereas no significant alterations were seen in PLP-C, PL-II or GHRP-1 levels. Northern blot analysis showed a 48% decrease in placental PLP-B steady state mRNA levels in LP animals. Thus, data indicate that a low protein, adequate calorie diet during pregnancy is associated with a selective decrease in PLP-B expression relative to other major secreted placental proteins during late gestation. Evidence further suggests a distinct role for PLP-B in feto-placental growth in this model for intrauterine growth retardation.

Expression of G proteins in human placentae from molar pregnancies

Hydatidiform mole is a conceptus, usually devoid of an intact fetus, with variable proliferation of trophoblast and altered placental protein synthesis, including high human chorionic gonadotropin (hCG) and low human placental lactogen (hPL) production. Little is known about the control of the production of these two placental proteins in molar pregnancies. Regulatory guanine 5′ triphosphate (GTP)-binding proteins (G proteins) play key roles in the endocrine control of peptide production by the placenta. The present authors recently demonstrated that Gig, Gi3 Go, and Gs α-subunits were expressed in normal human placenta throughout pregnancy. This study analysed the expression of placental G protein α-subunits in molar pregnancies. Western and Northern blot analyses were performed on membrane protein and total mRNA preparations of human placentae, respectively, from hydatidiform mole ( n=5) and normal pregnancies ( n=4). The levels of hPL and β-hCG mRNAs were 60 and 237 per cent respectively, of those from normal placentae. The autoradiographs for G proteins and their mRNAs showed decreased expression in molar placentae in comparison with normal tissues. Specifically, Gαi2, Gαi3, Gαo, and Gαs levels reached 39, 4, 42, and 89 per cent, respectively, of those from normal placentae. In parallel with the protein levels, their mRNAs expression were 8, 3, 54 and 65 per cent of normal values for Gαi2, Gαi3, Gαo, and Gαs, respectively. The results demonstrate important changes in placental G protein expression in hydatidiform moles suggesting alterations in the signal transduction machinery within the molar trophoblast.

Developmental regulation of glucocorticoid-mediated effects on extracellular matrix protein expression in the human placenta.

The extracellular matrix (ECM) protein fibronectin (FN) is a critical regulator of uterine-placental adherence. In the present report we compared the effects of glucocorticoids on FN expression in cytotrophoblast cultures isolated from human first trimester and term placentas to elucidate potential steroid-dependent cellular mechanisms associated with human parturition. Based on immunoassays, treatment of first trimester cytotrophoblasts with 10(-7) M dexamethasone (DEX) for 2 cr 4 days reduced medium levels of oncofetal FN (onfFN; i.e. FNs bearing an oncofetal epitope) to approximately 80% of control levels. Conversely, treatment of cytotrophoblasts isolated from term placentas with DEX dramatically reduced medium levels of onfFN to approximately 12% of control values. Treatment of both first trimester and term cells with 10(-6) M progestin, mineralocorticoid, or estrogen had no significant effect on onfFN expression in either cell type. Glucocorticoids specifically down-regulated medium levels of onfFN in term cells, but not in first trimester cells. In contrast, DEX treatment promoted an approximately 3- to 7-fold increase in levels of hCG in both first trimester and term cytotrophoblasts, suggesting that the effects of glucocorticoid on FN and hCG expression are elicited through independent cell-signaling pathways. In first trimester cells, DEX promoted a reduction in rates of FN and laminin synthesis to 60-70% of control levels. In term cells, DEX treatment reduced levels of FN and laminin synthesis to approximately 10% of control levels. Similarly, DEX treatment down-regulated levels of FN mRNA to approximately 60% and 10% of control values in first trimester and term cells, respectively. The first trimester of human pregnancy is associated with low levels of glucocorticoids and reduced glucocorticoid responsiveness. These conditions would favor high levels of placental ECM protein synthesis, thus stabilizing uterine-placental adherence. Conversely, elevated levels of glucocorticoids near parturition and increased glucocorticoid responsiveness would inhibit placental ECM protein synthesis, reducing uterine-placental adherence and promoting the separation of placenta from uterus.

The relationship of uterine and umbilical Doppler resistance to fetal and placental protein synthesis in the second trimester

The relation of uteroplacental and umbilical Doppler resistance index (RI) to peripheral levels of alphafetoprotein (AFP), human chorionic gonadotrophin (hCG), human placental lactogen (HPL), Schwangerswaft protein (SP1), pregnancy-associated placental protein A (PAPP-A) and insulin-like growth factor binding protein 1 (IGP-BP1) at 16-24 weeks was established in a cross-sectional study of 183 unselected singleton pregnancies. There was an association between high values of uteroplacental RI and high hCG levels, and high umbilical RI values with high hCG and HPL levels. Thus, in the mid-trimester, the levels of some placental proteins seem to be related to placental resistance.

Secretory and Morphological Changes in the Baboon (Papio Anubis) Uterus and Placenta during Early Pregnancy1

The study was undertaken to characterize changes in uterine endometrial secretory activity and morphology in the baboon between Days 18 and 32 of pregnancy. Proteins synthesized by the implantation site endometrium (RI) and non-implantation site endometrium (RIII) and developing placenta were analyzed by two-dimensional PAGE and fluorography. The electrophoretic mobility and localization of chorionic gonadotropin (CG) in the baboon placenta, and insulin-like growth factor binding protein-1 (IGFBP-1) and retinol binding protein (RBP) in the baboon uterus were confirmed by Western blot analysis and immunocytochemistry. Placental protein synthesis was primarily characterized by the presence of radiolabeled CG at Days 18 and 25, which decreased by Day 32. Peak CG synthetic activity, immunolocalized to the syncytiotrophoblast, occurred during the formation of tertiary villi. Also associated with the development of mature villi was a corresponding increase in a basic protein (M(r) 23,000). The overall secretory pattern of the baboon endometrium was similar to that observed during the midluteal stage; however, the synthetic activity was enhanced during pregnancy. Radiolabeled and immunoreactive IGFBP-1 and RBP were detectable in the Day 32 functionalis and basalis, respectively, and their synthesis was higher in RI compared to RIII. The immunolocalization of IGFBP-1 in RI appeared to be directly related to the degree of decidualization. In addition, a novel group of low molecular-weight (M(r) 27,000-30,000) isoelectrovariant proteins was secreted predominantly by the basalis at Days 18 and 25 of pregnancy and disappeared by Day 32 in all but one animal. The synthesis of this group of proteins did not show regional specificity. These studies indicate that the baboon endometrium undergoes morphological and secretory changes during pregnancy that are associated with the development of a functional placenta and decidualized endometrium. Furthermore, these studies suggest that the conceptus/placenta may mediate specific changes in IGFBP-1 and RBP expression at the implantation site.

Autoregulation of HCG and placental protein synthesis during trophoblast differentiation

The HLA class Ib antigen, HLA-G, is highly expressed in early gestation placentas where it is believed to modulate maternal-fetal immunological interactions. In this study, soluble isoforms (sHLA-G) encoded by intron 4-retaining transcripts were identified in first trimester placentas by immunohistochemistry using a mAb specific for the C-terminus of sHLA-G. Immunoreactive sHLA-G protein was localized to trophoblast cells and to villous mesenchymal cells with the morphological features of macrophages. Reverse transcriptase polymerase chain reaction analysis which used primers specific for intron 4 and the 3′ untranslated region of the HLA-G gene showed that transcripts encoding sHLA-G were present in the trophoblast-derived Jeg-3 cells as well as interferon-γ-activated myelomonocytic U937 cells but were absent and uninducible in placental fibroblasts. These results indicate that placental sHLA-G is synthesized in trophoblast cells and activated placental macrophages and support the postulate that placenta-derived sHLA-G modulates maternal and fetal immune cell functions during pregnancy.

Localization and synthesis of placental tissue protein 19 (PP19) in malignant tumors

Localization and synthesis of placental tissue protein 19 (PP19) in malignant tumors

Steroid regulation of oncofetal fibronectin expression in human cytotrophoblasts

Oncofetal fibronectin (onfFN) is a uniquely glycosylated form of FN suggested to play a critical role in uterine/placental adherence during pregnancy. In the present study we have examined steroid regulation of onfFN in highly purified preparations (⩾95%) of cytotrophoblasts isolated from human term placentas. Based on immunoassays, relative to controls, treatment of cytotrophoblasts with 10 −6M medroxyprogesterone acetate (MPA) down-regulated media levels of onfFN 25,53,59, and 62% on days 1,2,3 and 4,respectively. The pattern of steroid regulation and levels of total FN were nearly identical to that of onfFN suggesting that chronic steroid treatment regulates synthesis of FN and not its oncofetal glycosylation. MPA treatment induced a 2-fold stimulation in media levels of hCG indicating that increased placental function was associated with steroid-mediated changes in FN expression. Steroid specificity experiments demonstrated that MPA, cortisol, and dexamethasone were potent inhibitors of onfFN expression whereas estradiol (E2), deoxycorticosterone, testosterone, progesterone, and the synthetic progestin OD-14, were not. This suggested that glucocorticoids and not progestins may be the physiologic regulators of placental FN expression and that MPA may mediate its matrix-modifying activity through a glucocorticoid-like mechanism. Treatment of cells with dexamethasone (10 -7M) did not affect the levels of total protein synthesis or the release of human placental lactogen to the culture medium. This indicated that steroid-mediated down-regulation of onfFN expression in cytotrophoblasts did not result from a general reduction of protein synthesis. Based on densitometric scanning of Western blots, MPA and dexamethasone treatments down-regulated media levels of onfFN 70% relative to control levels. Northern blotting revealed that MPA and dexamethasone mediated a 60–90% reduction in steady state levels of FN mRNA in the presence or absence of E2. Our in vitro model may provide a unique system to evaluate steroidal effects on extracellular matrix (ECM) protein expression. In addition, we suggest that steroids may critically regulate placental ECM protein synthesis, and thus affect trophoblast/uterine adherence throughout pregnancy and expulsion of the placenta and membranes following delivery of the fetus.

Protein turnover in rat placenta: effects of maternal fasting and maternal protein restriction.

Biochemical composition and variables of protein turnover were determined in rat placenta at 21 days gestation in control animals and in animals subjected to 72-h fasting and protein/calorie restriction (6 per cent protein) throughout gestation. Placental protein synthesis was determined following the injection of 'massive' amounts of 14C-phenylalanine intravenously to the pregnant rat. Protein content was reduced in placentas from rats that were fasted for 72 h and in those who were protein restricted throughout pregnancy. Placental RNA content was significantly reduced only in the protein-restricted animals. Fractional rates of protein synthesis were reduced in placentas from the protein-restricted animals (Ks = 17.9 +/- 0.8 per cent per day in controls versus 11.7 +/- 0.9 in protein restricted, P = 0.002), but not in fasted animals. Fractional protein breakdown was markedly enhanced in placentas following maternal fasting (Kd = 9.9 per cent per day in controls versus 26.0 per cent in fasted), but not affected by protein deprivation. These results mimic those previously reported for other fetal tissues under these experimental conditions.

Changes in Endometrial and Placental Protein Synthesis and Morphology during Pregnancy and Pseudopregnancy in the Cat1

This study was undertaken to determine the effect of the implanting cat blastocyst on endometrial morphology and protein synthesis. Placental and endometrial tissues were obtained from pregnant and pseudopregnant cats and then cultured with L-[35S]methionine and analyzed for protein synthesis by 2-dimensional polyacrylamide gel electrophoresis followed by fluorography, and also processed for light microscopy. The progesterone-dependent protein (PDP), described previously by Boomsma and Verhage (Biol Reprod 1987; 37:117-126) and Verhage et al. (Biol Reprod 1989; 41:347-354), was identified by immunocytochemical and immunoblot analysis. Attachment began after 12 days, and the deep glands contained large deposits of PDP. By 20 days the placenta was well developed, and the deep endometrial glands under the placenta had regressed and lacked deposits of PDP. The placenta continued to develop and thicken as pregnancy progressed. The surface epithelium in the non-implantation site regions developed extreme convolutions, while the well-developed deep glands with large deposits of PDP began to regress by 4 weeks, becoming similar to those in the implantation site. The endometrial glands in the pseudopregnant animals maintained deposits of PDP even though apoptotic bodies were observed between 20 and 35 days. PDP synthesis was not detected in the implantation site after 16 days, but it continued in the nonimplantation site through 5 weeks. The synthesis of nine other proteins was significantly altered by the end of implantation such that the pattern in the non-site endometrium was different from the implantation site but similar to the pattern found in the pseudopregnant endometrium. As pregnancy progressed, protein synthesis was altered in the placental/junctional zone and the non-site endometrium, but in the deep endometrial portion of the implantation site it was largely unchanged and similar to the deep portion of the non-site. Thus, the implanting cat blastocyst has a significant effect on the morphology of the implantation site and non-site endometrium, and alters the protein synthetic activity of the implantation site endometrium but apparently not the non-site region. The morphology and protein synthetic patterns of the pregnant cat uterus show regional differentiation and continue to change as pregnancy progresses.

Progesterone Maintenance of the Placental Progesterone Receptor and Placental Growth in Ovariectomized Rats1

These studies examine the trophic effects of progesterone (P) on the progesterone receptor (Rp) and growth of the decidua basalis (DB) and junctional zone (JZ) in the rat placenta. Pregnant rats were ovariectomized (Ovx) in mid-pregnancy and received steroid replacement therapy consisting of implantation of P pellets (25 mg) and injections of estradiol (E), 2 micrograms s.c., daily. Placental protein synthesis, measured by 3H-leucine incorporation in vitro, decreased more than 99% within 24 h of Ovx. However, treatment with P immediately after castration maintained control levels of synthesis. Delay of P treatment for 4 h caused a 60% decline in protein production measured 20 h later (p less than 0.01). Intraperitoneal implantation of a 50-mg pellet of the antiprogestin, RU-38486, in intact pregnant rats decreased protein synthesis by 50% within 6 h and by more than 90% 12 h and 24 h post-implantation (p less than 0.01). Growth of DB and JZ in Ovx rats treated for 48 h with P and/or E was studied both histologically and by changes in protein and DNA content. Rp binding activity was also measured by exchange assay under equilibrium conditions. Only P was able to reverse the effects of Ovx on growth of the DB and JZ. P also maintained Rp levels in the DB above those observed in Ovx and Ovx + E-treated groups (p less than 0.01). The Rp may be a constitutive product in the JZ since binding activity was not altered by Ovx or by steroid treatments. This study shows that P is clearly a trophic hormone of the maternal and chorioallantoic placenta and is essential for placental growth, cellular differentiation, and histological integrity.

Regulation of protein synthesis in the first trimester human placenta by 17β-oestradiol and progesterone

Addition of 17 beta-oestradiol or progesterone to first trimester human placental explants in vitro resulted in the stimulation of protein synthesis, as seen by autofluorographic analysis of placental tissue and medium proteins. An increase in the incorporation of [35S]methionine into trichloroacetic acid-precipitable proteins was seen, following the addition of 17 beta-oestradiol. Use of aromatase inhibitor to block the synthesis of 17 beta-oestradiol inhibited the protein synthesis and while addition of cyclohexamide blocked both basal- and 17 beta-oestradiol-induced protein synthesis, actinomycin-D blocked only 17 beta-oestradiol induced protein synthesis. Double labelling of placental proteins in the presence and absence of 17 beta-oestradiol also indicated that there is a significant stimulation of protein synthesis by 17 beta-oestradiol. Based on these results it is suggested that oestradiol has a role in regulation of placental protein synthesis.

Characterization of Proliferin-Related Protein

Proliferin-related protein (mPRP) is a member of the PRL/GH family in the mouse. We have generated an antiserum against mPRP expressed as a bacterial fusion protein; this antiserum detects mPRP in the conditioned media of placental tissue cultures as a heterogeneous population of glycoproteins. We have also expressed mPRP in mammalian tissue culture cells and purified the secreted protein. N-terminal sequence analysis of the purified protein reveals that it is secreted as a 214 amino acid protein after removal of a 30 amino acid signal polypeptide. An antiserum raised against the purified protein detects high levels of mPRP in maternal serum during gestation. The site of synthesis of this protein has been localized by in situ hybridization to the basal zone of the day-10 mouse placenta, which is distinct from the site of synthesis of other placental proteins in this family.