Artifacts in the radioimmunoassay of ACTH in tissue extracts and plasma

Artifacts in studies employing the radioimmunoassay of ACTH may be introduced by the presence of high concentrations of protein or other substances which interfere in the antigen-antibody reaction and by unsuspected damage to the labeled ACTH. We have confirmed the reports of others that extracts of pancreatic, gastrointestinal and other nonpituitary tissues do decrease the binding of labeled ACTH to specific antibody. However, since all known forms of ACTH bind to and can be quantitatively eluted from QUSO, and the apparent immunoreactivity in these tissues does not, we conclude that there is no authentic ACTH detectable in the gut.