Immunocytochemical localization of parotin subunit in submandibular glands of the Japanese Monkey, Macaca fuscata

To determine the intracellular localization of parotin subunit in monkey submandibular glands, parotin subunit antiserum labeling and immunogold labeling were performed at both light and electron microscopic levels. Parotin subunit was found to be distributed along tonofibrils of striated duct cells, and to be localized intensely in middle electron-dense areas and less intensely in the dense core of secretory granules of serous acinar cells. Therefore, parotin subunit is secreted by serous cells and speculated to play a role in the formation of tonofibrils in duct apical region.