We are investigating mechanisms through which cAMP regulates specific differentiated cell function and cell growth. Purification, characterization, and study of the function of cAMP-dependent protein kinase are in progress. The processes through which cAMP induces alpha-amylase synthesis in parotid and pancreatic tissues are being studied using a specific anti-amylase antibody and a cell-free protein-synthesizing system for quantitation of alpha-amylase messenger RNA. Growth control is being studied in functional adrenal tumor cells in tissue culture where ACTH and cAMP stimulate steroidogenesis but inhibit cell replication. Cell cycle kinetics and mutant selection techniques are being used as an approach to definition of the mechanisms through which cyclic nucleotides effect cell growth.