Inactivation of Adrenocorticotropic Hormone in Vitro by Tissues*

The fact that frequent injections of adrenocorticotropic hormon (ACTH) are necessary in order to achieve a maximum physiological or clinical effect, along with the rapid disappearance of adrenocorticotropic activity from plasma which has been demonstrated to occur after intravenous injection of the hormone (Sayers et al 1949; Greenspan el al. 1950), and the inability of Richards and Sayers (1951) to find hormonal activity in the urine indicate that the hormone is rapidly destroyed or utilized in the organism. In order to determine the contributions of various tissues to the loss of ACTH activity, a study was made of theinactivation of the adrenocorticotropic hormone in vitro by organ slices and homogenates. METHODS The data reported here were obtained in two separate series of experiments. The first series was conducted in 1947–1948, and some of the results of these experiments have been reported elsewhere in a preliminary note (Li, 1948).