Pregnancy-associated Protein Research Articles

Quantitative analysis of a novel pregnancy-associated protein in trophoblastic diseases, normal pregnancy and healthy female subjects.

By means of the Laurell rocket technique, a novel pregnancy-associated protein was measured in the serum of patients with trophoblastic diseases as well as in pregnant women. In 52 normally-menstruating women, the serum levels were below the detection limit in 40 (76.9%); 50 women (96.2%) had levels of less than 2.0 U/ml, and none had levels above 2.1 U/ml. Of 25 patients with a hydatidiform mole, 23 (92.0%) had elevated levels (greater than 2.2 U/ml). In 84 healthy pregnant women, the levels rose from being undetectable before 5 weeks to a plateau in the second trimester. The results suggest that the appearance of this protein in serum is associated with trophoblastic activity.

An ovarian cancer-associated antigen that crossreacts with a pregnancy-associated protein

The presence of an ovarian ascitic antigen that crossreacts with a placental antigen was demonstrated in ascitic fluid from patients with advanced ovarian cancer, and the antigen was partially purified. Immunodiffusion and immunoelectrophoresis were employed to confirm the existence of the reactive antigen and to determine the relationships between the antigens from various sources. On double immunodiffusion, the ovarian ascitic antigen was found to be immunologically completely identical with a placental antigen against monospecific antisera raised against an ovarian ascitic and a placental antigen, respectively. On gel filtration on Sephadex G-200, the antigenic activity was eluted in two regions corresponding to different molecular sizes. The two preparations of the larger and smaller forms showed complete identity on double immunodiffusion, but dissimilar mobilities on immunoelectrophoresis. Preliminary characterization of the antigen revealed that it is distinct from several cancer-related antigens so far described.

High molecular weight angiotensinogen: a pregnancy associated protein

Although it was previously recognized that human amniotic fluid contained appreciable quantities of angiotensinogen, it remained unknown what fraction of the total is high molecular weight angiotensinogen. Fractionation of human amniotic fluid showed that high molecular weight angiotensinogen represents the major component of total angiotensinogen; 58% for 11 normotensive pregnant women and 67% for 12 hypertensive pregnant women. In contrast to plasma where high molecular weight angiotensinogen is elevated in hypertensive pregnant women as compared to normotensive pregnant women, no such difference exists for amniotic high molecular weight angiotensinogen. Serum and amniotic fluid high molecular weight angiotensinogen were compared in six subjects, and no significant correlation was found. In fetal cord blood, high molecular weight angiotensinogen represented only 5.8% of the total angiotensinogen. The site of synthesis of high molecular weight angiotensinogen remains unknown but these data suggest that it is produced in the placenta or in the maternal uterine tissue. Therefore, we propose that human high molecular weight angiotensinogen should be classified as a pregnancy-associated protein.

Detection of a pregnancy-associated protein

Monospecific antiserum was produced with the use of a placental extract showing high activity of a proteinase which hydrolyses a synthetic substrate, N-benzoyl- d,l-arginine p-nitroanilide, used for measuring tryptic activity. An immunological study showed that antibodies were not generated against the component with this activity but against an antigen which was not related to several well-known pregnancy-associated proteins. Pregnancy sera contained an antigen which immunologically was completely identical to the antigen of placental origin. Single radial immunodiffusion showed an elevated level of reactive antigen in pregnant subjects: 70% of 333 cases were positive. Cross-reacting antigen was also detected in sera as well as ascitic fluid from cases of advanced ovarian cancer. Sephadex G-200 gel filtration indicated that the antigen has an apparent molecular weight of 94000, and immunoelectrophoresis showed the molecule to be of β-mobility. These properties suggest that the substance may represent an additional pregnancy-associated protein entity. Partial purification and some immunological properties of this antigen are described.

Immunohistochemical localization of murine α1-pregnancy-associated protein ( α1-PAP) in pregnant mice: relationship between serum α1-PAP levels and incidence of positive cells

Using an electroimmunoassay, the murine pregnancy-associated protein α 1-PAP was detected in the sera of virgin MF1 but not C57BL/10 female mice. During pregnancy, α 1-PAP levels rose in both strains, although concentrations were higher in the latter and in both fell towards term. Using the unlabelled peroxidase anti-peroxidase (PAP) staining procedure, α 1-PAP was detected within mononuclear leukocytes, the majority resembling macrophages, in the small and large intestinal mucosae, Peyer's patches and hepatocytes of virgin MF1 but not C57BL/10 females. During pregnancy. α 1-PAP positive cells were observed in each of these sites and in the decidua and placenta of both strains. Quantitative studies revealed that the incidence of α 1-PAP positive cells in the gut and associated lymphoid tissues reflected the circulating levels of the protein. In the placenta, the frequency and intensity of α 1-PAP positive staining was also reduced towards parturition. In contrast, hepatocyte staining remained constant throughout gestation in both strains. Our observations suggest that there may be at least two types of α 1-PAP synthesis operative and that circulating levels of the protein in female mice are influenced by strain, pregnancy and stage of gestation. These findings are discussed in relation to the cell types involved, their contribution to serum levels and the possible role of α 1-PAP in fetal allograft survival.

The localization of pregnancy proteins (hPL, SP 1 and PAPP-A) in intra- and extrauterine pregnancies

The localization of human placental lactogen (hPL), pregnancy-specific beta-1 glycoprotein (Schwangerschaftsprotein 1, SP1) and pregnancy-associated protein A (PAPP-A) was examined in intrauterine and tubal ectopic gestation (n = 5) by the immunoperoxidase technique. The distribution of hPL and SP1 was identical in placental tissues obtained from intra- and extrauterine pregnancies, being uniformly seen throughout the syncytiotrophoblast. hPL and SP1 were not demonstrated in uterine decidual tissue from ectopic pregnancies. During early (week 8) intrauterine pregnancy, PAPP-A was not restricted to the mature syncytiotrophoblast, being observed also in some trophoblast-like cells adjacent to islands of syncytiotrophoblast. In contrast, in ectopic gestation, PAPP-A was observed in these cells at six weeks' gestation only. We were unable to detect PAPP-A in trophoblastic tissue of chorionic villi and uterine decidual tissue from ectopic gestation.

Identification of a murine pregnancy-associated serum protein (alpha 1-PAP) a female-specific acute-phase reactant.

A murine pregnancy-associated protein (alpha 1-PAP) with alpha 1-electrophoretic mobility and an estimated molecular weight of 150 000 was present in serum from pregnant C57BL/10 mice but could not be detected in serum of mature non-pregnant females and males. During pregnancy alpha 1-PAP was first detected on Day 7, rose to maximum levels between Days 12 and 14, and thereafter declined during the remainder of pregnancy and was undetectable by Day 8 post partum. The protein was also detected in the serum of females, but not males, subjected to an inflammatory stimulus. Examination of the alpha 1-PAP levels during an acute-phase response in females demonstrated that the protein behaved as a typical classical acute-phase reactant, although the levels were only 10% of those observed during Days 12 to 14 of pregnancy. alpha 1-PAP therefore appears to represent a hitherto undescribed female-specific acute phase reactant in the mouse.

An immunochemical study of proteins with SP1 determinants in native and acidified pregnancy serum.

The alpha and beta forms of the pregnancy-associated protein, SP1, have been studied in late pregnancy serum and in similar serum after acidification. In both sera only two forms of the protein, SP1 alpha and SP1 beta, could be found; both reacting with antisera against SP1. On gel chromatography these two forms could be separated, with the intermediate effluent containing a varying mixture of both proteins. Immunoelectrophoresis of the effluent fractions from gel chromatography showed rocket shaped immunoprecipitates whose morphology depended on the mixture of SP1 alpha and SP1 beta. Crossed immunoelectrophoresis confirmed that only two proteins could be defined with SP1 antisera; the front running protein having an alpha 2 electrophoretic mobility and a molecular weight of 430,000, while the slower moving component had the electrophoretic mobility of a beta 1 globulin and a molecular weight of 90,000.

Separation of two pregnancy-associated proteins with SP1 determinants and the conversion of SP1 beta to SP1 alpha.

The alpha and beta forms of the pregnancy-associated protein, SP1 which have been previously identified in late pregnancy serum were found to be also present in the placenta. The alpha form was somewhat more difficult to extract, requiring the use of detergents in the extracting buffer. The two variants can be separated by ion exchange chromatography or by gel filtration and distinguished by the different shapes of the precipitation rockets on immunoelectrophoresis. The alpha variant appears to be the larger molecule on gel filtration. When solutions of SP1 are acidified to pH 2.5 the beta form is rapidly converted to the alpha form and the latter is slowly destroyed. It is suggested that SP1 alpha represents the combination of SP1 beta with some other protein present in the placenta and in the serum.

Detection and synthesis of a progestagen-dependent protein in human endometrium.

Immunologiocal and biochemical methods were employed to demonstrate the presence of progestagen-dependent proteins in human endometrium. Cytosols were prepared from proliferative and secretory phase endometria of cycling women, from decidua and decidua-rich tissues of women in early pregnancy and from decidua of tubal pregnancy. Antisera were raised in rabbits against the antigens of decidua of tubal pregnancy and decidua-rich tissues. Immunoelectrophoresis, Ouchterlony's immunodiffusion test and polyacrylamide gel electrophoresis using native gels revealed 2 antigenic proteins, designated antigens A and B, in secretory endometria, decidua-rich tissues, decidua, and in decidua of tubal pregnancy. However, only 1 antigenic protein was detected by SDS-gel electrophoresis: antigens A and B may therefore be two different proteins or two forms of a single protein. The antigens could not be detected in non-pregnancy sera or in term placentae. Double isotopic labelling (incubation of tissues with [3H]- and [14C]leucine) followed by protein fractionation methods were used to compare the in-vitro synthesis rates of antigens in poroliferative tissues with those in decidua or secretory endometria. The rate of synthesis of antigens A and B was markedly higher in the decidua and secretory endometria than in the proliferative endometria. We conclude, therefore, that during progestagen-dependent transformation of proliferative phase endometria into secretory endometria and decidua in women, there is a selective stimulation of at least one species of pregnancy-associated protein.

Is SP-1 a marker for testicular cancer?

We measured the serum levels of the pregnancy-associated protein SP-1 by radioimmunoassay in 91 patients with a diagnosis of germ cell testicular cancer. Sixty-seven of the men had active disease, and of these, 52 per cent had elevated levels of SP-1. In contrast, all 24 patients with inactive disease had normal levels. Elevations of SP-1 were associated more often with elevated levels of human chorionic gonadotropin than with elevated levels of alpha fetoprotein, but elevated SP-1 levels also occurred in patients with normal levels of both of these established tumor markers. We studied serial samples from 21 patients, and in 5 the SP-1 level provided clinically valuable information not provided by the other two markers. SP-1 is a clinically useful marker in germ cell testicular cancer. Further studies are needed to determine the role of the two forms of protein, alpha and beta, and to define the conditions under which the SP-1 level is elevated.

The serum alkaline phosphatase of pregnancy

1.1. Boyer's6 observations on the occurrence of distinct alkaline phosphatase components in serum during pregnancy were confirmed with the use of a new technique.2.2. The pregnancy phosphatase was detected during a population study because of its characteristic electrophoretic mobility in starch gel following incubation of serum with neuraminidase. The association with pregnancy was established by reference to birth records, and was confirmed by testing 20 sera obtained from mothers at the time of delivery, and also by demonstrating the presence of the unusual phosphatase during sequential pregnancies and its absence between the pregnancies.3.3. The phosphatase was distinguished from another pregnancy-associated protein, namely, the alpha-2 globulin of pregnancy.4.4. The role which the placenta may have in the induction of these proteins is discussed.