Immunohistochemical localization of carboxylesterase in the nasal mucosa of rats

The enzymatic esterase activity of carboxylesterases is integral to the nasal toxicity of many esters used as industrial solvents or in polymer manufacture, including propylene glycol monomethyl ether acetate, dimethyl glutarate, dimethyl succinate, dimethyl adipate, and ethyl acrylate. Inhalation of these chemicals specifically damages the olfactory mucosa of rodents. We report the localization and differential distribution of a 59 KD carboxylesterase in nasal tissues of the rat by immunohistochemistry. Rabbit antiserum against the 59 KD rat liver microsomal carboxylesterase bound most prominently to the olfactory mucosa when applied to decalcified, paraffin- embedded sections of rat nasal turbinates. Within the olfactory mucosa, anti- carboxylesterase did not bind to sensory neurons, the target cell for ester- initiated toxicity; these cells apparently lack carboxylesterase. Instead, the antibody was preferentially bound by cells of Bowman's glands and sustentacular epithelial cells which are immediately adjacent to the olfactory nerve cells. In contrast, non-olfactory tissues (respiratory mucosa and squamous epithelium), which are more resistant to the toxicity of esters, had less carboxylesterase content. The distribution of immunoreactivity correlated well with the distribution of carboxylesterase catalytic activity described elsewhere. These findings help to link the metabolic fate of inhaled esters to the site-specific pathological findings that follow exposure to such chemicals.