This project is designed to evaluate the nature of lactogenic hormone receptors and the factors (including other hormones) that affect the binding of the hormone to this molecule. Studies include: 1) purification of the receptor from human tissue and preparation and characterization of an antibody against it; 2) examination of the nature of the subunits of the receptor; 3) characterization of the nature of the interaction of Tamoxifen with membrane-bound receptors related to the lactogen receptor; and 4) definition of the relationship of monoclonal antibody B6.2 to human lactogenic hormone receptors.