Immunohistochemical localization of metallothionein in the olfactory pathway of dogs

Dogs raised in the open air were used in this study. Metallothionein (MT) immunoreactivity was observed in the nucleus and/or cytoplasm of sustentacular cells of the olfactory epithelium in the nasal mucosa, whereas there was few MT-positive cells in the respiratory epithelium. MT immunoreactivity was also observed in astrocytes in all layers of the the olfactory bulb cortex; glial cells surrounding the glomeruli in the olfactory bulb showed prominent immunoreactivity for MT. Adult dogs exhibited stronger immunoreactivity for MT than young. Northern blot analysis demonstrated substantial levels of MT mRNA in the olfactory mucosa and olfactory bulb. Physiological roles of MT localized in the olfactory pathway of dogs were discussed.