EFFECTS OF DICHLOBENIL ON ULTRASTRUCTURAL MORPHOLOGY AND CELL REPLICATION IN THE MOUSE OLFACTORY MUCOSA

The herbicide dichlobenil (2,6-dichlorobenzonitrile) is a tissue-speci fic toxicant inducing necrosis in the olfactory mucosa. Transmission e lectron microscopy showed vacuolations (1 hr) and necrosis (4 hr) in t he Bowman's glands following intraperitoneal injection of dichlobenil (25 mg/kg) in C57BI mice, whereas no lesions were noted in the olfacto ry neuroepithelium at these timepoints. Twenty-four hr following injec tion (25 mg/kg), most of the lamina propria and the olfactory epitheli um were severely damaged; the basal lamina, nerves, and blood vessels in the lamina propria, however, remained intact. Following a lower dos e (12 mg/kg), the lesions were not as pronounced. The effects of dichl obenil (6, 12, and 25 mg/kg) on cell replication in the olfactory muco sa, as determined by incorporation of H-3-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 neuroepith elium, Together these studies support the previous proposal that dichl obenil induces a primary damage in the Bowman's glands.