Figure 4.

Distribution of the olfactory epithelium (marked in green) and the respiratory epithelium (marked in blue) at the posterior portion of the nasal passage (T3) of rats exposed to FA+CO (A). 1-NN injury was quite similar between the FA-exposed and O₃-exposed rats and occurred in all types of the epithelia that lack goblet cells at T3. The goblet cell–containing epithelium was not injured from 1-NN (data not shown). Olfactory mucosal injury from 1-NN was region-specific, unlike other types of epithelia, and it was confined only to the olfactory epithelium lining the dorsal medial meatus (DMM, shaded in red) at 6 hours after 1-NN treatment (B). At 24 hours after 1-NN treatment, the area of olfactory mucosal injury from 1-NN also included the small area (shaded in blue) of the middle portion of the nasal septum (B). High-resolution histopathology of the olfactory epithelium (C and D), the respiratory epithelium in the main nasal passage (E and F), and the respiratory epithelium in the maxillary sinus (G and H) is shown at 6 hours after CO (C, E, and G) or 1-NN (D, F, and H) treatment. Arrowheads, basement membrane; arrows, polymorphonuclear cells; bg, Bowman's glands; c, cilia from olfactory receptor cells; gl, gland; n, nerve bundle; ns, nasal septum; o, olfactory receptor cells; s, sustentacular cells; * vacuole.