Specific Demonstration of the Human Hypophyseal Cells Which Produce Adrenocorticotropic Hormone

Abstract

An antiserum was produced in rabbits against a synthetic polypeptide corresponding to amino acids 17–39 of porcine adrenocorticotropic hormone (17–39 ACTH). This ACTH fragment lacks amino acid sequences in common with any known melanocyte-stimulating hormone (MSH). The 17–39 ACTH antiserum was used in the immunoglobulin-peroxidase bridge technique to immunostain sections of the human hypophysis. Cells in the immunostained sections were identified by their morphology and coloration in serial sections stained with an alcian blue-periodic acid Schiff-orange G reference stain. The 17-39 ACTH antiserum reacted only with the β or R type cells and immunostained almost all these cells in the pars distalis and in the pars nervosa. The ACTH cells which stained red with the reference procedure often revealed weak or no immunostaining, whereas those colored blue-purple were strongly immunostained. Thus, blue-purple and red ACTH cells might represent stages in a maturational sequence or a secretory cycle. Radioimmunoassay studies, and the results of immunostaining after absorption with synthetic ACTH and MSH, demonstrated the specificity of the 17-39 ACTH antiserum for human ACTH. The finding of ACTH exclusively in the human β or R type cells refutes previous hypotheses that the cells produce only β-MSH and clarifies earlier studies in which immunofluorescent staining of the cells with ACTH antisera was inconclusive because of possible cross-reactivity with MSH. Since only the β or R type cells revealed localization of the 17-39 ACTH antiserum, it appears unlikely that ∈,γ, or follicular cells produce ACTH, as has been postulated.