Effects of dichlobenil on ultrastructural morphology and cell replication in the mouse olfactory mucosa

The herbicide dichlobenil (2,6-dichlorobenzonitrile) is a tissue-specific inducing necrosis in the olfactory mucosa. Transmission electron microscopy showed vacuolations (1 hr) and necrosis (4 hr) in the Bowman's glands following intraperitoneal injection of dichlobenil (25 mg/kg) in C57B1 mice, whereas no lesions were noted in the olfactory neuroepithelium at these timepoints. Twenty-four hr following injection (25 mg/kg), most of the propria and the olfactory epithelium were severely damaged; the basal lamina, nerves, and blood vessels in the lamina propria, however, remained intact. Following a lower dose (12 mg/kg), the lesions were not as pronounced. The effects of dichlobenil (6, 12, and 25 mg/kg) on cell replication in the olfactory mucosa, as determined by incorporation of 3H-thymidine 3 days later, were more pronounced in the lamina propria than in the neuroepithelium and occurred at a lower dose in the lamina propria than in the neuroepithelium. Together these studies support the previous proposal that dichlobenil induces a primary damage in the Bowman's glands.