Our goal is elucidation on the molecular level of the steroid endocrine processes concerned with human development and reproduction and utilization of the results for the solution of biomedical and clinical problems. Our major concern is sex steroids, androgen aromatases, antibodies to aromatase, and their molecular reactions and interactions. Specific aims are: (1) Purification and characterization of multiple forms of aromatase from human term placenta, (2) Production and utilization of antibodies against aromatase, (3) Elucidation of mechanism of androgen aromatization, (4) Irreversible inhibitors and affinity labeling of aromatase, and (5) Solubilization, purification, and characterization of brain aromatase system. Androgen aromatase or estrogen synthetase is an enzyme which catalyzes the conversion of androgen to estrogen. Estrogens play many important physiological roles through human development and are essential to reproduction. They are also involved in diseases including breast and endometrium cancer. Precise knowledge of the properties of this enzyme and the specific antibodies may have important practical implications in reproductive endocrinology, fertility regulation, and diagnosis and control of carcinogenesis. Development of irreversible inhibitors of aromatase may lead to a chemotherapeutic application as a means of endocrine therapy to control estrogen dependent carcinomas. The methodology involves synthesis of steroids with and without deuterium, tritium, carbon-13, carbon-14 and oxygen-18 labels at stereoselective and/or regiospecific positions, conformational analysis by crystallography and spectroscopy, isotope distribution analysis, incubations with various enzyme preparations, solubilization of membrane bound enzymes with detergents, procedures to maintain enzymes in solution after removal of detergents, purification of enzyme through various chromatographies including immunoaffinity resins, identification of intermediates and products of aromatase reaction by use of isotope techniques and GC-MS, immunization of animals, hybridoma cultures, screening specific antibodies by micro-aromatase assays, production of monoclonal antibodies in ascites fluid, purification of immunoglobulins, immunohistochemical stainings, radioimmunoassays, Western blot analysis, amino acid analysis, and amino acid sequencing.