Influence of blood glucose levels on serum concentrations of pregnancy-specific protein SP-1 and HPL during the last trimester of pregnancy

Molecular cloning of a cDNA for human pregnancy-specific beta 1-glycoprotein:homology with human carcinoembryonic antigen and related proteins

Human pregnancy-specific beta 1-glycoprotein (SP1) plays an essential role in normal pregnancy. It is also a well-characterized oncodevelopmental antigen, expressed aberrantly by all trophoblastic tumors and some other malignant cell types. Here we report the identification of a human placental cDNA encoding the SP1 polypeptide sequence. The coding sequence shows 95% identity at the nucleotide level with a distinct, recently published SP1 cDNA sequence (PSG16). Unexpectedly, the sequence is also highly homologous to the published sequence of human carcinoembryonic antigen (CEA). SP1, CEA and CEA-related nonspecific cross-reacting species thus belong to a group of closely related though antigenically diverse tumor-associated glycoproteins. Comparison of the deduced amino acid sequence of the SP1 cDNA with that of CEA provides insight into the modular nature of these related proteins. This may have implications for the genomic organization and evolution of the CEA gene family.

New placental proteins: chemistry, physiology and clinical use

In the past decade, several new placental proteins have been isolated and studied. The 'pregnancy-specific' beta 1-glycoprotein (SP1) is a major placental product with unusual physicochemical properties that has been extensively investigated, but its biological function remains uncertain. Pregnancy-associated plasma protein A (PAPP-A), a glycoprotein of mol. wt 400,000, has effects in vitro on the coagulation and complement cascades, probably by its properties of protease inhibition. Placental protein 5 (PP5) may be involved in the coagulation and fibrinolytic systems, and in follicle maturation and semen liquefaction. 'Placental protein 12' (PP12) is not a product of the placenta at all; it appears to be produced in the female genital tract under the influence of progesterone and may also be produced by proliferating liver cells. Further study may reveal new roles for these placental proteins beyond their traditional roles as tumour markers.

Studies on the concentration of pregnancy-associated plasma protein-A during normal and complicated pregnancy

Pregnancy-associated plasma protein-A was assayed in the blood of 347 women during pregnancy, using a new primary standard of PAPP-A as reference. The protein was assayed by antibody-antigen crossed electrophoresis with the lower limit of confident assay being 9.5 micrograms PAPP-A/ml (13 pmol/ml). PAPP-A was first detected at 14 weeks of gestation; by term it had risen to within the range 20 to 320 micrograms/ml. There was an indication that pregnancies involving a male baby had higher PAPP-A levels in blood than did those involving female babies. In 51 blood samples from 30 patients with gestational diabetes (taken between 28 weeks of pregnancy and term) there was no significant alteration in PAPP-A values compared with controls. In 35 blood samples from 15 patients with insulin-dependent diabetes, levels of PAPP-A were significantly lower than in controls or in gestational diabetes. In 43 blood samples from 35 patients with babies affected with intrauterine growth retardation (between 28 weeks and term), there was no significant difference in PAPP-A levels compared with controls. The effect of insulin on the blood levels of PAPP-A suggests that the concentration of PAPP-A is capable of altering significantly in response to certain physiological changes associated with the control of carbohydrate metabolism.

Circulating levels of pregnancy specific beta 1 glycoprotein in pregnancies complicated by diabetes mellitus

Circulating levels of SP1 were measured in 20 insulin dependent diabetic women during the third trimester of pregnancy. With one exception, SP1 levels were between the 80 per cent confidence limits of the normal range. The exception was a patient who was delivered of a normal infant at 37 weeks but had consistently low levels of SP1 from 32 weeks until delivery, suggesting a specific defect in SP1 synthesis.

The relation between pregnancy specific beta 1 glycoprotein (SP1) levels and abnormal glucose tolerance in pregnancy

Pregnancy specific beta 1 glycoprotein (SP1) levels were measured in 54 potentially diabetic patients in the third trimester of pregnancy using a laser nephelometric method. All patients were tested by the 50 g oral glucose tolerance test. The results show that a significantly greater number of patients with abnormal glucose tolerance had SP1 levels above the mean compared with patients with normal glucose responses. All patients with a diabetic type response had SP1 levels above the mean. There was no significant difference in SP1 levels in the fasting and two-hour plasma samples. The study suggests that patients with asymptomatic glucose intolerance in pregnancy have higher SP1 levels than patients with normal glucose tolerance. It is possible that one of the factors controlling the placental output of SP1 is the maternal blood glucose level.

The plasma half-life of placental hormones

Blood was collected from 12 women following Caesarean section or normal delivery at term. The decline in plasma concentration of total oestriol, oestriol sulphate, oestriol glucosiduronate, unconjugated oestriol, human placental lactogen and pregnancy specific beta1 glycoprotein following delivery of the placenta was studied for 120 hours. The steroids and human placental lactogen fell very rapidly but pregnancy specific beta1 glycoprotein declined much more slowly. Analysis of the curves of puerperal decline suggests that the oestriol moieties are distributed in many compartments of the mother but that the proteins penetrate only to the plasma and the interstitial fluid.

[Concentration of pregnancy-specific-beta-1-protein sp1 in amniotic fluid in normal and pathologic pregnancies (author's transl)]

The concentration of the pregnancy specific protein SP-1 in amniotic fluid was determined in normal and pathologic pregnancies. SP-1 concentrations in amniotic fluid of normal pregnancies amounted to one percent of the maternal serum concentrations. In cases with diabetes mellitus intrauterine death and rhesus incompatibility SP-1 levels were increased significantly.