The Endocrinology of Pregnancy and Parturition

Current Topics in Experimental Endocrinology, Vol. 4

L Martini, V. H. T. James

• Publisher: Academic Press
• Year: 2013
• Print ISBN: 9780121532048
• eBook ISBN: 9781483217369
• Topic: Biological Sciences
• Subtopic: Physiology
• Index: Biological Sciences

Current Topics in Experimental Endocrinology, Volume 4: The Endocrinology of Pregnancy and Parturition deals with the various aspects of pregnancy and parturition. The book discusses pregnancy and parturition in marsupials; the vital role of the corpus luteum; and the endocrinology of the preimplantation period, looking into the variety of hormones and other agents and their involvement in the implantation process. The text also describes the critical role of prolactin in pregnancy; the role of human chorionic gonadotropin in early pregnancy; and specific pregnancy proteins. The clinical use of human placental lactogen in pregnancy; estrogen and progestrone production in human pregnancy; and the role of oxytocin in parturition; threatened abortion are also considered. Endocrinologists, obstetricians, gynecologists, reproductive physiologists, and students taking related courses will find the book invaluable.

Specific Pregnancy Proteins

Arnold Klopper, Department of Obstetrics and Gynaecology, University of Aberdeen, Aberdeen, Scotland

Publisher Summary

This chapter provides an overview of specific pregnancy proteins. A woman with a hydatidiform mole is pregnant but carries no fetus. A placenta—or at least trophoblastic tissue—is more essential to the definition of pregnancy than a fetus. By the same reasoning, specific pregnancy proteins are proteins produced only by the placenta. Probably all cells carry the code for the full range of proteins, which the organism is capable of synthesizing. In the case of the specific pregnancy, proteins are repressed in all but the placenta and certain primitive tissues such as fibroblasts and some tumors. The definition of a pregnancy protein is quantitative, not absolute. But the difference in the amount of specific pregnancy protein produced by the placenta and the traces produced by nontrophoblastic tumors or fibroblast cultures is so much that there is no difficulty in operating the distinction in practice. A pregnancy protein is quantitative, not absolute.

I Introduction

II Schwangerschaftsprotein 1 (SP₁) 129

A Historical Note

B The Chemistry of SP₁ 130

C SP₁ in Other Animals 133

D The Origin of SP₁ 133

E The Measurement of SP₁ 134

F The Metabolism of SP₁ 136

G SP₁ in Normal Pregnancy 137

H Pathological Pregnancy

I The Function of SP₁ 146

III Pregnancy-Associated Plasma Protein A (PAPP-A)

A Historical Note

B The Chemistry of PAPP-A

C The Assay of PAPP-A

D The Origin of PAPP-A

E The Metabolism of PAPP-A

F PAPP-A in Normal Pregnancy

G PAPP-A in Pathological Pregnancy

H The Function of PAPP-A

IV Pregnancy-Associated Plasma Protein B (PAPP-B)

A Historical Note

B Chemistry of PAPP-B

C The Physiology of PAPP-B

D Future Studies on PAPP-B

V Placental Protein 5 (PP5)

A Historical Note

B Chemistry of PP5

C Origin of PP5

D PP5 in Normal Pregnancy

E PP5 in Abnormal Pregnancy

F The Function of PP5

VI Other Pregnancy-Associated Proteins

VII Envoy

References

I Introduction

A woman with a hydatidiform mole is pregnant but carries no fetus. A placenta, or at least trophoblastic tissue, is more essential to the definition of pregnancy than a fetus. By the same reasoning specific pregnancy proteins are proteins produced only by the placenta. For our purposes this is still too embracing a definition, although it conveniently excludes nonplacental proteins such as sex hormone binding globulin or pregnancy-associated globulin, both of which increase greatly during pregnancy but are not of placental origin. By the same token pregnancy-associated proteins such as ∝-fetoprotein are also excluded. The exclusively placental protein is itself no more than a convenient fiction. Probably all cells carry the code for the full range of proteins which the organism is capable of synthesizing. In the case of the specific pregnancy proteins it is repressed in all but the placenta and certain primitive tissues such as fibroblasts and some tumors. In the final analysis the definition of a pregnancy protein is quantitative, not absolute. But the difference in the amount of specific pregnancy protein produced by the placenta and the traces produced by nontrophoblastic tumors or fibroblast cultures is so great that there is no difficulty in operating the distinction in practice.

I propose to operate two further exclusions for reasons of convenience rather than logic. This survey will be confined to proteins secreted by the trophoblast into the maternal circulation in increasing amounts as pregnancy advances. This excludes interesting newly isolated proteins such as the proteins of the syncytial microvilli which sit at the interface between mother and conceptus, the structural proteins of the placenta and functional proteins such as ferritin receptors engaged in transplacental transport. Lastly, established placental hormones such as hCG and hPL are also excluded. This leaves a number of proteins such as Schwangerschafts protein 1 (SP₁), pregnancy-associated plasma proteins A and B (PAPP-A and PAPP-B), and placental protein 5 (PP5), all of which are presumed to be synthesized in the trophoblast and released into the maternal blood stream. Even so the list is open ended—new ones are being added month by month. For our purposes the list will be restricted to those placental proteins about which a sufficient body of clinical data has accumulated to be worthy of comment.

II Schwangerschaftsprotein 1 (SP₁)

When Bohn (1971) isolated this protein, he called it Schwangerschaftsprotein 1 (SP₁). It has also variously been called pregnancy-specific β₁-globulin (Tatarinov et al., 1976a), pregnancy-associated plasma protein C (Lin et al., 1974a), and pregnancy-specific β₁-glycoprotein (Towler et al., 1976a). For a while the last designation, contracted to PSβ₁G, held sway as it seemed a more specific chemical description. Then other pregnancy-specific β-glycoproteins were recognized and the name PSβ₁G had to be abandoned. At a meeting in 1979, it was agreed by investigators working on this protein to revert to Bohn’s term SP₁ until a functional description could be derived (Halbert, 1979).

A Historical Note

During the 1960s a number of new proteins with β₁, electrophoretic mobility were recognized in the sera of pregnant women. Possibly the protein now called SP₁ was among them, but it was not sufficiently characterized, chemically or immunologically, for it to be identified with the protein known today. The credit for the first description of SP₁ goes by a narrow margin to two Russian investigators, Tatarinov and Masyukevich, who in 1970 demonstrated a new β₁ from the sera of pregnant women. They were followed in short order by Hans Bohn who independently isolated from human placentas a β₁-glycoprotein in 1971. Bohn characterized his protein so clearly that subsequent investigators had little difficulty in recognizing it when it appeared in placental extracts or in the purification of pregnancy plasma. A somewhat different approach did in fact lead to another independent recognition of SP₁. This was the technique used by Gall and Halbert (1972) who injected whole pregnancy serum into rabbits. By doing so they of course raised a spectrum of antibodies to the proteins in the serum of a pregnant woman. By absorbing out such an antiserum with serum from a nonpregnant individual, they were able to remove all the antibodies to normal serum proteins, leaving behind only antibodie...

Table of contents

• Cover image
• Title page
• Table of Contents
• Contributors
• Editorial Board
• Copyright page
• Contributors
• Preface
• Pregnancy and Parturition in Marsupials
• The Endocrinology of the Preimplantation Period
• Prolactin and Pregnancy
• Human Chorionic Gonadotropin in Early Pregnancy
• Specific Pregnancy Proteins
• Human Placental Lactogen
• Estrogen and Progestrone Production in Human Pregnancy
• The Role of Oxytocin in Parturition
• Threatened Abortion
• Index