This project is designed to evaluate the nature of lactogenic hormone receptors and the factors (including other hormones) which affect 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, and 3) characterization of the nature of the interaction of Tamoxifen with membrane-bound receptors related to the lactogen receptor.