Localization of a 16,000-dalton fragment of the common precursor of adrenocorticotropin and beta-lipotropin in the rat and human pituitary gland.
To clearly identify cells and organelles containing the common precursor (31,000 dalton) for both adrenocorticotropin (ACTH) and beta-lipotropin (beta-LPH), an immunohistochemical localization of a fragment (16,000 dalton) of the precursor that is not common to beta-LPH and ACTH was conducted in rat and human pituitary glands. With the help of specific antibodies that do not cross-react with beta-LPH and ACTH, the 16,000-dalton fragment was localized in the cells that also produce ACTH and beta-LPH in both the pars distalis and pars intermedia of the rat pituitary. At the electron microscope level, the secretory granules that contain ACTH were also stained for 16,000-dalton fragment. In the human pituitary, the 16,000-dalton fragment was also observed in all the secretory granules of lipocorticotrophs. These results suggest that, after enzymatic cleavage, fragment(s) of the common precursor and/or the whole common precursor remain packaged within the secretory granules with peptides of known activity.
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D006801:Humans; D007158:Immunologic Techniques; D008297:Male; D008854:Microscopy, Electron; D008970:Molecular Weight; D010902:Pituitary Gland / Q000378:metabolism* / Q000648:ultrastructure; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D008083:beta-Lipotropin / Q000378:metabolism*
D011498:Protein Precursors; D000324:Adrenocorticotropic Hormone; D008083:beta-Lipotropin