USE OF PROTEIN A COATED COLLOIDAL GOLD PARTICLES FOR IMMUNOELECTRONMICROSCOPIC LOCALIZATION OF ACTH ON ULTRATHIN SECTIONS

ACTH was localized in dissociated porcine adenohypophysial cells using a novel indirect EM immunocytochemical technique. Incubation of ultrathin resin sections in anti-ACTH was followed by incubation with protein A-coated colloidal gold particles. Protein A binds specifically to the Fc part of the IgG molecule, and thus the ACTH-containing secretory granules became labelled with electron-dense gold particles. With this method, the dissociated porcine ACTH cell was identified as containing numerous round or ovoid 170-300 nm, secretory granules. © 1979 Springer-Verlag.