In this research project we will study the significance of endocrine factors in the metabolism of normal and leukemic leukocytes. One of the approaches will be to investigate the formation and metabolism of iodocompounds in leukocytes. According to the preliminary results, it seems that human circulating leukocytes concentrate iodine and forms metabolize released iodinated compounds. We will compare the iodine metabolism in normal leukocytes and white blood cells at different stages of development and we will also study the effect of phagocytosis on iodine metabolism in normal and leukemic cells. This project is also designated to investigate the relationship between cyclic adenosine 3', 5'-monophosphate (cAMP) production and the stage of leukocyte differentiation and maturation. The iodine metabolism in leukocytes and cAMP formation are also closely related because we were able to show that cAMP regulates iodine metabolism in white blood cells. One of the most important parts of this project is to study the significance of a factor found in the pituitary that regulates the metabolic activity of leukocytes.