ULTRASTRUCTURAL IMMUNOGOLD LOCALIZATION OF OSTEOPONTIN IN HUMAN GASTRIC-MUCOSA

We performed ultrastructural immunogold localization of osteopontin in the mucosa of human stomach. This adhesive glycoprotein was present i n mucous and chief cells of the epithelial layer and in macrophages in the lamina propria. Parietal and endocrine cells of the epithelial la yer and mast cells and plasma cells in the lamina propria did not cont ain osteopontin, serving as internal negative controls. Subcellular lo calizations of osteopontin included secretory granules and synthetic o rganelles in mucous and chief cells and phagolysosomes in macrophages. Extracellular concentrations of osteopontin were present in the glyco calyx and in an electron-lucent band between epithelial surface cells and the gastric lumen. Paracellular edema between the epithelium of th e same cells was devoid of osteopontin. Immunogold localization of pep sinogen II was done to identify cells with mixed granule populations a nd contents of multicompartmental secretory granules. These studies re vealed mucous cell granules and chief cell granules, each containing c ompartmentalized storage products, which included osteopontin and muci gen in mucous cells and osteopontin and pepsinogen II in chief cells. Cytochemical controls for the immunogold localizations were negative. The subcellular distribution of osteopontin in human Mucigen gastric m ucosa suggests possible roles for this glycoprotein in barrier functio n, host defense, and/or secretion.