Immunochemical studies of adrenocorticotropin using tritium labeled hormone

A radioimmunoassay using specifically tritiated corticotropin (<SUP>3</SUP>H-ACTH) of high specific radioactivity (46 Ci/mmol) and full biological activity has been developed. The assay is sensitive to ACTH in the range 200 pg-10 ng. 50% displacement of <SUP>3</SUP>H-ACTH is produced by less than a twofold excess of unlabeled hormone. Immunochemical studies with various ACTH analogs showed that the antiserum recognized the intact molecule better than any of the fragments