Two fetal antigens (FA-1 and FA-2) and endometrial proteins (PP12 and PP14) isolated from amniotic fluid; preliminary observations in fetal and maternal tissues

Rabbit antihuman antibodies were derived by the injection of fractions of second trimester amniotic fluid known to contain proteins of endometrial/decidual origin. Using standard separation and absorption procedures, two antibody preparations were generated which demonstrated specificities against two and three proteins, respectively, in line immunoelectrophoresis and crossed immunoelectrophoresis. Analysis against proteins of fetal, maternal, endometrial and placental origin revealed that the bispecific antiserum reacted only with placental protein 14 (PP14; also known as progestagen-dependent endometrial protein, PEP) and one other hitherto undescribed antigen referred to as Fetal Antigen 1 (FA-1) molecular mass 60 kDa; electrophoretic mobility: slow; alpha 1-alpha 2; fast, albumin. The trispecific antiserum demonstrated specifities against placental protein 12 (PP12), alpha-fetoprotein (AFP) and another previously undescribed antigen referred to as Fetal Antigen 2 (FA-2) molecular mass 35 and 140 kDa; electrophoretic mobility: albumin. Following purification, monospecific antisera against each of these proteins (with the exception of AFP) were derived in new rabbits. Maternal and fetal blood, amniotic fluid and aqueous extracts from endometrial/decidual and placental tissues were analysed in rocket immunoelectrophoresis using these antisera to examine the distribution in these tissues. The analyses demonstrated a pattern of distribution typical for proteins of endometrial/decidual origin in these compartments in the case of PP12 and PP14, but suggested that the primary source of origin of FA-1 and FA-2 may be the fetus.

Immunofluorometric demonstration and quantification of placental protein 5 in the absence of pregnancy

This time-resolved immunofluorometric assay (IFMA) developed for measurement of placental protein 5 (PP5) involves two antibodies: a monoclonal anti-PP5 antibody attached to a solid phase and an europium(III) chelate-labeled polyclonal anti-PP5 antibody as a tracer. The measuring range is 0.05-100 micrograms/L and the detection limit is 20 times lower than that of a PP5 radioimmunoassay (RIA) performed with the same polyclonal antiserum. By IFMA, PP5 could be detected and quantified in all plasma and serum samples of nonpregnant and pregnant individuals, whereas PP5 was undetectable by RIA in serum of healthy men and nonpregnant women. The mean concentration of PP5 in sera from men was 0.43 micrograms/L (SD 0.13, range 0.19-0.75, n = 47) and in sera from nonpregnant women 0.49 micrograms/L (SD 0.19, range 0.20-0.90, n = 41). PP5 concentrations in serum showed no systematic variation during the menstrual cycle. In serum samples from 60 pregnant women the results obtained by IFMA and RIA correlated well (r = 0.97).

Immunofluorometric demonstration and quantification of placental protein 5 in the absence of pregnancy

This time-resolved immunofluorometric assay (IFMA) developed for measurement of placental protein 5 (PP5) involves two antibodies: a monoclonal anti-PP5 antibody attached to a solid phase and an europium(III) chelate-labeled polyclonal anti-PP5 antibody as a tracer. The measuring range is 0.05-100 micrograms/L and the detection limit is 20 times lower than that of a PP5 radioimmunoassay (RIA) performed with the same polyclonal antiserum. By IFMA, PP5 could be detected and quantified in all plasma and serum samples of nonpregnant and pregnant individuals, whereas PP5 was undetectable by RIA in serum of healthy men and nonpregnant women. The mean concentration of PP5 in sera from men was 0.43 micrograms/L (SD 0.13, range 0.19-0.75, n = 47) and in sera from nonpregnant women 0.49 micrograms/L (SD 0.19, range 0.20-0.90, n = 41). PP5 concentrations in serum showed no systematic variation during the menstrual cycle. In serum samples from 60 pregnant women the results obtained by IFMA and RIA correlated well (r = 0.97).

High molecular weight forms of insulin-like growth factor II and its binding protein identified by protein immunoblotting

Insulin-like growth factor (IGF)II is a mitogenic polypeptide which circulates in association with a binding protein(s). Immunoblotting studies were performed in human serum and indicate that:(1)a approximately 200 kDa covalently-linked IGF-II/binding protein complex is antigenically related to the 30 kDa binding protein, (2)IGF-II prohormone is associated with this complex, and (3)a major portion of the IGF-II prohormone immunoreactivity in human serum is present in fractions which would not be detected by standard radioimmunoassay methods. Our data provide insight regarding the inter-relationships of IGF-II and its binding protein, and direct evidence for the presence of IGF-II prohormone in human serum.

Insulin-like growth factor (IGF) binding protein from human decidua inhibits the binding and biological action of IGF-I in cultured choriocarcinoma cells

The placenta expresses genes for insulin-like growth factors (IGFs) and possesses IGF-receptors, suggesting that placental growth is regulated by IGFs in an autocrine manner. We have previously shown that human decidua, but not placenta, synthesizes and secretes a 34 K IGF-binding protein (34 K IGF-BP) called placental protein 12. We now used human choriocarcinoma JEG-3 cell monolayer cultures and recombinant (Thr59)IGF-I as a model to study whether the decidual 34 K IGF-BP is able to modulate the receptor binding and biological activity of IGFs in trophoblasts. JEG-3 cells, which possess type I IGF receptors, were unable to produce IGF-BPs. Purified 34 K IGF-BP specifically bound [125I]iodo-(Thr59)IGF-I. Multiplication-stimulating activity had 2.5% the potency of (Thr59)IGF-I, and insulin had no effect on the binding of [125I] iodo-(Thr59)IGF-I. 34 K IGF-BP inhibited the binding of [125I] iodo-(Thr59)IGF-I to JEG-3 monolayers in a concentration-dependent manner by forming with the tracer a soluble complex that could not bind to the cell surface as demonstrated by competitive binding and cross-linking experiments. After incubating the cell monolayers with [125I]iodo-(Thr59)IGF-I in the presence of purified binding protein, followed by cross-linking, no affinity labeled bands were seen on autoradiography. In contrast, an intensely labeled band at 40 K was detected when the incubation medium was analyzed, suggesting that (Thr59)IGF-I and 34 K IGF-BP formed a complex in a 1:1 molar ratio. Also, 34 K IGF-BP inhibited both basal and IGF-I-stimulated uptake of alpha-[3H]aminoisobutyric acid in JEG-3 cells. RNA analysis revealed that IGF-II is expressed in JEG-3 cells. We conclude that decidual 34 K IGF-BP inhibits the cellular binding and biological action of IGFs in JEG-3 cells. Our data show that JEG-3 cells represent a cell type that can produce IGF, but not IGF-BPs. These cells may thus provide a useful model system for a better understanding of autocrine growth regulation mediated by the IGFs.

Monoclonal antibodies reacting with placental protein 5: use in radioimmunoassay, Western blot analysis, and immunohistochemistry

Monoclonal antibodies were raised reacting with placental protein 5 (PP5), a glycoprotein with properties of a serine protease inhibitor. Immunization was carried out with an antigen purified from late pregnancy placenta tissues. After fusion with myeloma cells, clones producing antibodies reacting with PP5 were isolated. Antibodies produced by two of the established hybridoma clones were characterized. The Ka of the antibodies was 0.22 x 10(9) L/mol and 0.3 x 10(8) L/mol. in Western blot analysis, both monoclonal antibodies reacted with the purified antigen that had a relative molecular weight (Mr) of 30 kd, but minor components of Mr 27 kd, 56 kd, and 62 kd were also identified. In polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate under reducing conditions, the purified protein yielded three polypeptides (Mrs of 16.4 kd, 16.8 kd, and 18.3 kd) that did not react with the monoclonal antibodies in Western blot analysis. By immunoperoxidase staining with monoclonal and polyclonal antibodies, PP5 was localized to the syncytiotrophoblast, cytotrophoblast, and endothelium of early and late pregnancy placenta tissues, whereas various other tissues were PP5-negative. In immunofluorescence staining, isolated endothelial cells were stained with both monoclonal antibodies. Endothelial cells in monolayer culture released into the medium a substance that is immunologically similar to purified PP5.

Purification and characterization of placental protein 5

This report describes the purification of placental protein 5, PP5, from the human placenta by two affinity chromatography steps, the first with Heparin-Sepharose and the second with Sepharose-linked monoclonal anti-PP5 antibody. The final purification is achieved by reversed-phase high performance liquid chromatography. In SDS-polyacrylamide gel electrophoresis under reducing or nonreducing conditions, PP5 purified in this study migrates as one major band at 36 kD. The previously purified PP5 is more heterogeneous: under nonreducing conditions it migrates at 30 kD and, after reduction, it gives three bands at 16.8 kD, 18.3 kD, and 19.0 kD. In Western blot analysis, both purified proteins react with polyclonal and monoclonal anti-PP5 antibodies. Three N-terminal amino acid sequences are obtained for the previously purified PP5, whereas the N-terminal of PP5 purified in this study is blocked. These results suggest that PP5 previously purified in the absence of protease inhibitors, does not represent the native form of PP5. Computer comparison of the obtained amino acid sequences revealed no significant homology to known protein sequences.

Serum PP12, PP14, SP1 and hCG values in the 28 days after the LH-surge in patients who do and do not conceive after artificial insemination or in vitro fertilization

Serum levels of PP12 (somatomedin binding protein), PP14 (beta lactoglobulin homologue), Schwangerschaftsprotein 1 (SP1) and of human chorionic gonadotropin (hCG) were simultaneously measured in patients being treated for infertility in the 28 days after the LH-surge. PP14 levels were similar in the 14 days after the LH-surge in the patients who conceived when compared with those who did not and a high PP14 level was only indicative of pregnancy at 21 days after the LH-surge. hCG and SP1 levels behaved similarly in pregnant subjects. PP12 levels did not change significantly in the 28-days after the LH-surge.

Placental protein 21. Localization in human placenta and concentrations in the body fluids of men and nonpregnant and pregnant women

The immunohistochemical localization of placental protein 21 (PP21) was marked in the syncytial brush border and basal membrane during the 1st and 2nd trimesters of pregnancy and also in the chorionic epithelial brush border and basement membrane at term. A weaker stain was found in the cell membranes of amniotic epithelial and chorionic trophoblast cells. Neither heparin nor changes in temperature significantly influenced PP21 concentration. Relatively high serum PP21 concentrations were measured during the follicular and luteal phases in healthy nonpregnant women and in healthy men whose seminal plasma also showed a high PP21 concentration. Serum PP21 levels in normal pregnancy rose from a median of 29.1 ng/ml at 6-7 weeks of gestation to 82.0 ng/ml at 36-37 weeks of gestation. Although maternal urine showed low PP21 levels during pregnancy, amniotic fluid PP21 levels were higher at 7-21 weeks of gestation than at term. Cord blood sera showed almost the same PP21 concentration as maternal sera, but retroplacental blood showed much higher levels. Maternal serum PP21 levels in hydatidiform mole patients did not differ from the normal pregnancy range, although their molar vesicular fluids contained higher PP21 concentrations. These results suggest an extraplacental source for PP21.

Beta lactoglobulin homologue placental protein 14 (PP14) in serum of patients with trophoblastic disease and non-trophoblastic gynecologic malignancy

Serum levels of beta lactoglobulin homologue placental protein 14 (PP14) were measured by a sensitive radioimmunoassay in various trophoblastic diseases and non-trophoblastic gynecologic malignancies. While trace amounts of protein were detected in sera of non-pregnant subjects (22.3 +/- 13.7 micrograms/l), during first half of normal pregnancy a dramatic rise of serum-PP14 levels was demonstrable with a peak-value at 7th-10th week of gestation, followed by a decline thereafter. Serial determinations of PP14 have been performed in 31 patients with trophoblastic tumour (20 hydatidiform moles, 4 invasive moles and 7 choriocarcinomas). In patients with hydatidiform moles and invasive moles (273.5 +/- 106.5 micrograms/l and 162.2 +/- 109.6 micrograms/l) respective values before therapy were much exceeding the non-pregnant controls. After therapy there was a rapid decline of the serum-PP14 levels within two weeks. In patients with choriocarcinoma the PP14 values were moderately elevated (66.4 +/- 25.7 micrograms/l), and declined following the remission of disease. In 32 gynecological tumours (21 carcinomas of the cervix, 4 endometrial carcinomas, 5 ovarian carcinomas, 2 carcinomas of the vulva) the pretreatment levels were not different to normal controls.

Characteristic differences in immunohistochemical localization of new placental proteins (PP1, PP19, PP21) in the human placenta

The immunohistochemical localization in the human placenta of new placental proteins PP1, PP19, and PP21 was clarified using modified indirect enzyme-labeled antibody method and compared with that of pregnancy-specific beta 1-glycoprotein (SP1). The major results are as follows: positive staining for PP1 was seen at the nucleus and cytoplasm of villous cytotrophoblasts, the X cells at the basal plate, and of chorionic trophoblasts, while the decidua cells and amnion were not stained. PP19 was characteristically seen in the nucleus and cytoplasm of syncytiotrophoblasts. X cells in basal plate, chorionic trophoblasts, and maternal leukocytes. The villous cytotrophoblasts, decidua cells, and amnion were not stained. PP21 localization was found at the microvilli and basal membrane of syncytiotrophoblasts and at the cytotrophoblast plasma membrane of the chorionic villus in early gestation. In late gestation, increased staining was seen at the syncytiotrophoblast microvilli and the villous basement membrane, and moderate staining at plasma membrane of the amniotic epithelium and chorionic trophoblasts. SP1 was found only at the syncytiotrophoblast cytoplasm of chorionic villi. Studies using these four placental proteins simultaneously may therefore provide a new key learning about unknown metabolic functions of trophoblasts.

Oncoplacental protein SP1--a constitutive and inducible late differentiation marker of the human myelomonocytic lineage

The oncoplacental protein SP1 is found in large quantities in human placenta, amniotic fluid, and pregnancy serum. Low levels have been reported in association with malignancy but also in healthy nonpregnant individuals. By indirect immunofluorescence, fluorescence-activated cell sorting, and immunoprecipitation we here demonstrate the presence of SP1 both on the surface and in the cytoplasm of human granulocytes but not in earlier myeloid progenitor cells in bone marrow. Lymphocytes did not contain the protein, and only trace amounts could be found in the cytoplasm of blood monocytes. A major glycoprotein with an apparent mol wt of 90,000 was obtained by immunoprecipitation of surface-labeled granulocytes. Cultivated blood monocytes, while adhering to surfaces or forming multinuclear giant cells, displayed a strong membrane and cytoplasmic expression of SP1. Treatment of the myeloid leukemia cell line ML-2 with tetraphorbol acetate (TPA) strongly induced SP1 in the membrane and cytoplasm as revealed by immunofluorescence and polyacrylamide gel electrophoresis (PAGE) of immunoprecipitates from lysates of surface radiolabeled cells. The induction of synthesis of SP1 in TPA-treated cells was confirmed by immunoprecipitation from lysates of cells metabolically labeled with 35S-methionine. Human lymphoblastoid and erythroleukemic cell lines did not express SP1 either before or after induced differentiation. Thus SP1 provides a late differentiation marker for the myelomonocytic lineage and is strongly induced during macrophage differentiation or by TPA treatment of ML-2 cells.

Amino acid sequence homology between human placental protein 14 and beta-lactoglobulins from various species

The primary structure of 22 N-terminal amino acid residues of placental protein 14 was determined by automated Edman degradation with a gas-phase sequencer. This protein, isolated from the human placenta and its membranes, was considered pure as evidenced by a single N-terminal amino acid sequence M D I P Q T K Q D L E L P K L A G T W H S M. It shows significant sequence homology with horse, bovine, buffalo, sheep and goat beta-lactoglobulins. We found 13 identities out of 22 possible matches with horse beta-lactoglobulin. beta-lactoglobulins from several animal species have been found to bind retinol. Among the identical residues there is one tryptophan at position 19 which is conserved in beta-lactoglobulins and is also found in the human retinol-binding protein at the corresponding position. These data suggest a common origin of PP14 and beta-lactoglobulins.

Isolation and characterization of a flavin-containing placental protein (PP3)

Placental protein 3 (PP3) has been isolated to purity from saline extracts of human term placentas. PP3 turned out to be a flavin-containing protein and thus appears to be an enzyme. The prosthetic group was identified as flavin-adenine dinucleotide (FAD) which was found to be noncovalently bound to the protein. The physical characterization of PP3 showed that the molecules are composed of two identical subunits having molecular weights of 55000 daltons which are noncovalently linked. Each subunit appears to contain one FAD group. In addition PP3 was found to have an electrophoretic mobility in between the alpha 1 and alpha 2 globulins, an isoelectric point in the range of 5.3-5.7, a sedimentation coefficient of 6.3 S and an extinction coefficient of 15.7 (E1%(1cm) 280 nm). Immunochemical methods were used to detect and quantitate PP3 in extracts of placentas and other human tissues. From one human term placenta an average of around 4 mg PP3 could be extracted; PP3 was also found to occur in extracts of adult human stomach. In concentrated extracts of other human tissues and in human body fluids this protein could not be detected, at least not in concentrations higher than 2 mg/dl.

Placental protein 10: levels in benign and malignant ovarian cyst fluids and pleural exudates

Placental protein 10 (PP10) was measured in benign (n = 47) and malignant (n = 10) ovarian cyst fluids and in pleural fluid specimens from 19 patients with pleural metastases of various carcinomas (n = 15) or infectious pleurisy (n = 4). PP10 was found in 9 out of 18 follicular or luteal cyst fluids (range 2.0-42.0 micrograms/l) and in 24 out of 29 benign ovarian tumours (range 2.6-38.0 micrograms/l). Nine out of ten malignant ovarian cyst fluids contained detectable PP10 (range 4.0-55.2 micrograms/l). PP10 was found in all the pleural fluids from 15 patients with metastatic bronchial, pulmonary, breast or pancreatic carcinomas (range 5.1-100.2 micrograms/l), as well as from four patients with pleurisy (range 5.0-28.6 micrograms/l). Our results indicate that PP10 is tumour-associated, but not tumour-specific.

The immunocytochemical localization of new soluble placental tissue proteins (PP14, 16, 17, 19, 20 and PP21) in human and cynomolgus monkey placentae

Apparently Placenta-specific placental tissue proteins (PP14 and PP17) and solitary tissue proteins (PP16, 19, 20 and PP21) were investigated by avidin-biotin immunoperoxidase technique in the human and cynomolgus monkey placentae, membranes, decidua and umbilical cords. In human early placentae, PP14, 16, 17, 19 and PP21 were localized mainly in the cytoplasm of villous syncytiotrophoblast. PP20 was localized in the cytoplasm of basal chorionic trophoblasts. In human term placentae, positive stainings for PP16, 19 and PP21 were observed mainly in all kinds of trophoblastic cells, while positive stainings for PP14, 17 and PP20 were weakened in the trophoblastic cells. PP20 was clearly localized in the cytoplasm of Hofbauer-like cells in the villous stroma. The membrane of villous syncytiotrophoblast showed strongly positive stainings for PP21. PP21 was also localized in the membrane of amniotic and umbilical epithelium. The umbilical epithelium was cytoplasmically positive for PP14, 16 and PP20. Clear positive stainings for PP14 and PP21 were found in the cytoplasm of fetal polymorphonuclear neutrophils. All of the placental proteins were immunocytochemically positive in the decidual large cells. In the cynomolgus monkey placentae, similar immunostaining results were obtained. The monkey could, thus, serve as a model for the investigation of the placental proteins.

In vitro and in vivo studies of the production of placental proteins (HCG, SP1, PPs) in human choriocarcinoma cell lines

The production of human chorionic gonadotropin (hCG), pregnancy-specific beta-1 glycoprotein (SP1), and the various placental tissue proteins (PP4, PP5, PP10, PP11, PP12, MP1) was examined in human choriocarcinoma cell lines using radioimmunoassay (RIA) and an immunoperoxidase (PAP) staining method. In 6 gestational and 2 nongestational choriocarcinoma cell lines, hCG was produced in vitro. A significant heterogeneity of hCG production was noted among the cell lines. Production of hCG in the xenograft tumors was consistent with the hCG production of the same cell lines in vitro. SP1 was demonstrated both in the culture supernatants and the xenograft tumors of 3 cell lines, and the production was found to be inversely correlated with the hCG production of the cell lines. Positive staining for PP4 and MP1, and weakly positive staining for PP5, PP10, and PP12 was found in the xenograft tumors by immunoperoxidase (PAP) stain, but the staining for PP11 was negative. These placental proteins showed positive staining in portions of choriocarcinoma cells. These results indicate that placental proteins are not equally produced in heterogeneous choriocarcinoma cells.

Biologically active domain in somatomedin-binding protein

We have found that human decidua synthesizes a 34K somatomedin-binding protein PP12. Purification of PP12 by immunochemical techniques from human placenta and adjacent membranes has also yielded lower-molecular weight immunoreactive polypeptides designated as PP12B. An individual 21K fragment of somatomedin-binding protein, and a mixture of fragments with molecular weight from 17K to 20K were isolated from this material using high performance liquid chromatography (HPLC). These fragments reacted with antibodies to native PP12 as shown by Western blotting. They all shared the same N-terminal amino acid sequence: Ala-Pro-Trp-Gln-, which is identical with that obtained for PP12. The 21K fragment was shown to bind somatomedin-C, or IGF-I (insulin-like growth factor-I). Since the N-terminal end of the 21K fragment is identical with that of the 34K somatomedin-binding protein, our results suggest that the 21K fragment is the N-terminal part of somatomedin-binding protein, and the somatomedin-binding domain resides in this N-terminal portion.

Technical notes on chronic fluid-filled catheters and renal artery constrictors for testing hemodynamic drug effects in conscious hypertensive dogs

Construction and chronic implantation of fluid-filled arterial and ventricular catheters and renal artery constrictors for testing hemodynamic drug effects in conscious dogs are described. The two catheters were made from commercially available silicone rubber and Tygon tubing connected by a molded silicone rubber plate. The blood pressure catheter was inserted via the superficial iliac artery into the abdominal aorta; and the left ventricular catheter, through the apex of the heart. Application of silicone rubber constrictors to both renal arteries resulted in the following hemodynamic values: BPs 180 +/- 4 mm Hg; BPd 111 +/- 2 mm Hg; LVPdp/dt max 3250 +/- 122 mm Hg/sec; and HR 82 +/- 4 beats/sec. Simultaneous recording of LVP and dp/dt signals with Millar Micro-Tip and fluid-filled catheters revealed a difference in signal form and size. Damping the LVP signal of the fluid-filled catheter either with a low-pass filter of 10-30 Hz or using 2-3% dextran solution as catheter fluid abolished this difference. However, a time lag and a difference in dynamic response to positive inotropic agents were still present. Based on our findings, fluid-filled ventricular catheters are recommended for routine work. The effects of antihypertensive, antianginal, and cardiotonic reference compounds could be easily detected with this methodology.

Synthesis of placental protein 12 by decidua from early pregnancy

The synthesis and secretion of placental protein 12 (PP12) by early pregnancy decidua and trophoblast were studied in vitro from tissues obtained by curettage during elective termination of pregnancy (weeks 8-14). The tissue explants were incubated in Ham's F-10 medium for a 27-h period, and the PP12 levels in media and tissue homogenates were measured by RIA. De novo synthesis of PP12 was assessed by measuring the incorporation of radioactivity into PP12 after 20 h of incubation of tissues with 20 microCi/ml [35S]methionine. PP12 from the culture medium was immunoprecipitated with anti-PP12(A) antiserum, and the immunoprecipitate was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The initial tissue content of PP12 was 10- to 72-fold higher in decidua than in trophoblast. The total amount of radioimmunoassayable PP12 released into medium by decidual explants during the 27-h incubation period together with that present in the tissues at the end of incubation exceeded the initial tissue content by 242.7 +/- 63.7% (mean +/- SE). Only small amounts of PP12 were detected in media from trophoblast cultures. During the first 7 h of incubation, inclusion of cycloheximide had no effect on PP12 release by decidual explants in three of four experiments. Between 7 and 27 h, the amount of PP12 released by cycloheximide-treated tissues was 20.0 +/- 7% of that released by control tissues (P less than 0.01). Cycloheximide had no effect on PP12 release by trophoblasts. Decidual explants incorporated [35S]methionine into PP12, but trophoblasts did not. In sodium dodecyl sulfate-gel electrophoresis, the newly synthesized PP12 comigrated with the major band of purified PP12 corresponding to mol wt 29,000. These data clearly confirm that PP12 is a protein of decidual rather than trophoblastic origin, and indicate that decidua from early pregnancy has the ability to synthesize it.

Human endometrium and menstrual fluid contain placental protein 5 (PP5)

Placental protein 5 (PP5), a serine protease inhibitor, was found in the endometrium and menstrual fluid of non-pregnant women. PP5 was present in all 16 endometrial samples taken at various phases of the menstrual cycle. In the secretory phase, the endometrial PP5 content was higher (median 17.4 micrograms/g protein; n = 8) than in the proliferative phase (median 3.8 micrograms/g protein; n = 8). In gel filtration, endometrial tissue homogenates yielded one immunoreactive peak corresponding to a mol. wt of 28,000 daltons, whereas placental PP5 eluted at 32,000 daltons. In sodium dodecyl sulphate polyacrylamide gel electrophoresis, endometrial PP5 comigrated with purified placental PP5 corresponding to a mol. wt of 30,000 daltons. All menstrual fluid samples (n = 14) contained immunoreactive PP5 at concentrations from 77 to 1150 micrograms/l. The mol. wt of menstrual fluid PP5-immunoreactivity was 13,000 daltons. The dose-response curves of purified PP5 standard and endometrial and menstrual fluid PP5 were parallel in the PP5 radioimmunoassay. The higher concentration of PP5 in secretory endometrium indicates association of PP5 with endocrine events of the menstrual cycle.

Immunochemical and biochemical relationship between human pregnancy-associated secreted endometrial alpha 1- and alpha 2-globulins (alpha 1- and alpha 2-PEG) and the soluble placental proteins 12 and 14 (PP12 and PP14)

Two proteins, pregnancy-associated endometrial alpha 1- and alpha 2-globulins (alpha 1- and alpha 2-PEG), synthesized de novo and secreted by the human endometrium and decidua during pregnancy, have been demonstrated to be immunochemically related to the soluble placental proteins PP12 and PP14 isolated from term placenta. However, although these immunochemically similar endometrially- and placentally-derived proteins differ in their reported biochemical properties, in this report we have demonstrated that PP12 and PP14 are biochemically identical to alpha 1- and alpha 2-PEG with respect to subunit size. We conclude that these placental proteins are derived from the endometrium by de novo synthesis, and we suggest that the localization of these proteins to the placenta reflects either absorption, specific binding or processing by the trophoblast. The significance of clinical studies involving PP12 and PP14 measurement must therefore be reassessed in the light of their exclusive endometrial origin.

Oligomerization of pregnancy-specific beta 1-glycoprotein (SP1) at physiologic pH and ionic strength

Highly purified pregnancy-specific beta 1-glycoprotein (SP1) migrated in gel electrophoresis as a homogeneous species and behaved as a single species in 6 mol/l guanidinium chloride (GdmCl), both in the ultracentrifuge and HPLC. At physiologic pH and ionic strength, in the absence of GdmCl, SP1 existed in the form of oligomers of apparent molecular weights of 40 000 to greater than 300 000. The specific activity of these oligomers varied over a 5-fold range. Electrophoretic mobility also varied among SP1 oligomers, with increasing (alpha-like) mobility shown by oligomers of increasing molecular size. Oligomerization may explain some or all of the reports of SP1 heterogeneity.