Resting human female breast tissue produces iodinated proteins

Normal resting human breast tissue was obtained from immediate autopsies performed on six women who had died from head injuries sustained in accidents. Tissue samples containing epithelium were dissected asceptically and either fixed immediately or placed into culture. Samples in culture for 2 or 3 days were exposed to radioiodide for 4 hr in order to establish whether or not the isotope became incorporated into proteins. Light and electron microscope autoradiographs were prepared and evaluated. Radiolabeled secretory material was observed in both the terminal ductules and intralobular terminal ducts, but not within the larger ducts. Therefore the products in these separate compartments of the mammary epithelial tree differ in composition. Extensive gap junctions were discovered between adjacent myoepithelial cells in the terminal ductules and intralobular terminal ducts. These junctions probably serve to coordinate contractions which facilitate the movement of material from the most distal parts of the gland into larger ducts.