Carolyn A. Campen

Chemical and biological characterization of the inhibin family of protein hormones.

Publisher Summary This chapter discusses the chemical and biological characterization of the inhibin family of protein hormones, which is a family of peptides isolated from the follicular fluid or rete testis fluid on the basis of their ability to inhibit the secretion of the follicle-stimulating hormone (FSH) by cultured rat anterior pituitary cells. It also reviews the possible roles of inhibin and fibre-reinforced plastic (FRP)/activin in placenta, brain, and bone marrow. Inhibin-related dimers are broadly distributed anatomically and have powerful activities in several biological systems where inhibin and FRP/activin often exhibit opposite effects. While the physiologic roles of inhibin to regulate FSH secretion in the female rat and immature male rat are strongly supported, the significance of these hormones within the gonad, brain, placenta, and bone marrow have yet to be placed in in vivo context. Although the panoply of functions of inhibin and FRP/activin are certainly incompletely understood at this time, this family has already demonstrated a powerful mechanism for the generation of signal diversity whereby differential subunit association can result in the generation of dimers with opposing biological actions in multiple tissues.

Detection and purification of inhibin using antisera generated against synthetic peptide fragments

Publisher Summary Inhibin is a hormone whose best established physiological role is selective suppression of the release of follicle-stimulating hormone (FSH) from the pituitary. Subsequent to the identification of inhibin, two laboratories isolated a protein from porcine follicular fluid that selectively released FSH from pituitary cell cultures. Characterization of this protein––named FSH releasing protein (FRP)/activin––showed that it was a homo- or heterodimer of inhibin β subunits. This chapter also describes the production of antibodies to the α, βA, and βB subunits of inhibin; development of a radioimmunoassay (RIA) specific for inhibin, using an antibody directed to the α subunit; use of these antibodies for Western blot analysis; and a method for concentrating inhibin and FRP from biological fluids. It also discusses a method that was developed for the rapid isolation of inhibin from ram rete testis fluid (RTF) using immunoaffinity chromatography with an antibody directed against the α subunit.

Evolution of a Model of Estrogen Action

Publisher Summary This chapter illustrates the evolution of a model of estrogen action. The unoccupied estrogen receptor (no estrogen ligand) is thought to be a nuclear protein bound to nuclear components by low affinity interactions. Cytoplasmic exclusion may also influence the nuclear localization. Estrogens are lipophilic and therefore can diffuse through cell membranes, cytoplasm, and nuclear envelope to interact with the nuclear receptor. As a result of this interaction rapid changes occur in the conformation of the receptor protein. These conformational changes result in the new physical properties, including a higher affinity for nuclear components which prevents low salt extraction of the transformed estrogen–receptor complex. The nature of the interaction between estrogen–receptor and nucleus is still unknown but nuclear components involved could include chromatin proteins, the nuclear matrix, DNA, or the various combinations of these. However, that estrogen binding to the receptor causes increased rates of transcription of a variety of genes, depending upon the respective target cell.

Nonsteroidal progesterone receptor ligands with unprecedented receptor selectivity

We have characterized a series of nonsteroidal progesterone receptor ligands, the tetrahydropyridazines. Compounds in this series, exemplified by RWJ 26819, demonstrate high affinity and unprecedented specificity for the progesterone receptor relative to other steroid hormone receptors. Like steroidal progestins, RWJ 26819 induces binding of the receptor to a progesterone response element in vitro, and stimulates gene expression in and proliferation of T47D human breast cancer cells. When administered to rabbits orally or subcutaneously, the compound induces histological changes in the uterine lining comparable to those induced by levonorgestrel. It also inhibits ovulation in monkeys. Though less potent in cells and in animal models than would be predicted from binding affinity alone, their enhanced selectivity suggests that they could be effectively used in a clinical setting. Most of the tetrahydropyridazines synthesized are progestin agonists or mixed agonists and antagonists in vitro; however, one compound with antagonist activity in the rabbit uterine transformation assay has been identified.

Synthesis and progesterone receptor binding affinity of substituted 1-phenyl-7-benzyl-4,5,6,7-tetrahydro-1H-indazoles

Abstract Research directed toward the discovery of non-steroidal ligands for steroid receptors led to the preparation of a series of substituted 1-phenyl-7-benzyltetrahydroindazole-3-carboxaldehydes. Appropriately substituted 3-formyl analogs (4) were found to bind with high affinity to progesterone receptors and showed agonist activity in human T47D cells but were inactive in several in vivo models for progestational activity.