Studies of hormonal regulation of cell function, growth, and replication are proposed. The mechanism of action of ACTH and cAMP will be studied in normal and neoplastic adrenal cortical tumor cells in vivo and in vitro. Purification and characterization of the cAMP-dependent protein kinase will be undertaken and the functional role of this enzyme will be evaluated. The mechanism of regulation of steroidogenesis in adrenal cortical cells will be studied. In addition, the mechanism of inhibition of DNA synthesis by ACTH and cAMP in functional adrenal tumor cells in tissue culture will be explored. Hormonal control of protein synthesis will be studied in cells in culture and in vitro systems using amylase messenger RNA. The functional significance of the poly A region of messenger RNA and of the hormone-dependent ribosomal phosphorylation will be explored using cell free protein synthesizing systems. The mechanism of ACTH and cAMP stimulation of RNA synthesis will be investigated in vitro systems using the isolated adrenal cortical RNA polymerase enzymes.