EVIDENCE FOR A PEPTIDE SIMILAR TO 16K FRAGMENT IN MAN. ITS RELATIONSHIP TO ACTH.

Abstract

A radioimmunoassay directed toward the NH₂-terminal region of mouse pro-ACTH⁄endorphin (called 16K fragment) was used to examine human samples. Culture media from two corticotropic adenomas and plasmas from 1 patients with various ACTH hypersecretory syndromes gave parallel displacement curves; displacement curves for human samples were not parallel to purified mouse 16K fragment. Following sodium dodecyl sulfate polyacrylamide gel electrophoresis of culture medium from one adenoma, a major peak of 16K fragment immunoreactivity with an apparent molecular weight of ca. 16,000 was detected. A significant correlation (r = 0.963 ; p < 0.001)was found between immunoreactive 16K fragment and ACTH in the patients’ plasmas. These data indicate that a peptide similar to 16K fragment exists in man ; that human and mouse 16K fragment are immunologically distinguishable and that human 16K fragment appears to be secreted concomitantly with ACTH.