Cellular localization of carnosinase in the human nasal mucosa.

The cellular localization of the enzyme carnosinase in human nasal mucosa was investigated using immunoperoxidase and double-staining immunoflourescence techniques. In the olfactory mucosa, carnosinase immunoreactivity was localized in the sustentacular cells, the acinar cells of Bowman's glands, and the perinuclear region of a small subset of olfactory receptor neurons. In the respiratory mucosa, carnosinase immunoreactivity was identified in the secretory vesicles of the epithelial goblet cells as well as in the respiratory glands. There was an age-related trend toward a decrease in the intensity of carnosinase immunoreactivity in the olfactory mucosae of older subjects. These results suggest that the role of carnosinase may be to provide the amino acids histidine and beta-alanine, the products of carnosine hydrolysis, to the amino acid pool for protein synthesis in the cells that secrete nasal mucus and in olfactory receptor neurons.