We are engaged in chemical, conformational, metabolic, and mechanism-of-action studies on several pituitary polypeptide hormones, e.g., growth hormone (GH), prolactin (PL), adrenocorticotropin (ACTH), and Luteinizing hormone (LH), and on human chorionic gonadotropin (HCG). Structure-function studies are being conducted on GH, PL, and fragments. For example, with GH we are investigating certain fragments for their ability to induce somatomedin and to stimulate ornithine decarboxylase activity. Physico-chemical studies are being conducted on the gonadotropins, LH and HCG, and on their subunits. We are mainly using the techniques of circular dichroism, difference spectroscopy, and hydrodynamics. The in vivo clearance and metabolism of GH, PL, ACTH, and LH is being actively studied. Comparative work is also being done with non-hormonal proteins and derivatives. A rat testis organ culture system is operative in which we measure gonadotropin binding, steriodogenesis, and cAMP following LH or HCG stimulation. This is for investigation of the gonadotropin residues essential for biological activity.