Effects of 0.12 and 0.80 ppm Ozone on Rat Nasal and Nasopharyngeal Epithelial Mucosubstances: Quantitative Histochemistry

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Abstract
The present study was designed to characterize the quantity of mucosubstances in surface epithelia of the rat nasal cavity and nasopharynx after short-term ozone exposure. Rats were exposed for 7 days (6 hr/day) to 0, 0.12, or 0.8 ppm ozone and were killed immediately or 7 days after the last exposure. Nasal cavities were processed for morphometric analysis of intraepithelial mucosubstances. Compared to controls, rats exposed to 0.12 ppm ozone had increased amounts of stored mucosubstances within epithelium lining the medial aspect of the nasal turbinate, but no change within the epithelium of the nasopharynx. Rats exposed to 0.8 ppm ozone had increased quantities of stored mucosubstances within the transitional and respiratory epithelia lining turbinates and lateral walls of the anterior nasal airway, and significant decreases in stored mucosubstances within the epithelium of the nasal septum at the end of exposure. Seven days after the end of exposure, the amounts of intraepithelial mucosubstances returned to control levels along the septum, but remained greater than those of controls along the turbinates and nasopharynx. We conclude that exposures to ambient levels of ozone induce significant changes in the stored secretory product of nasal epithelium in the rat, and that these changes persist for at least 7 days after cessation of exposure.