Biochemical and Morphologic Responses of Rat Nasal Epithelia to Hyperoxia

Biochemical and Morphologic Responses of Rat Nasal Epitheliato Hyperoxia. NIKULA, K. J., SABOURIN, P. J., FRIETAG, B. C,BIRDWHISTELL, A. J., HOTCHKISS, J. A., AND HARKEMA, J. R. (1991).Fundam. Appl. Toxicol 17, 675–683. While performing itsfunctions in olfaction, modification of inspired air, and protectionof the lower respiratory tract from high concentrations of potentiallyharmful inhalants, the nasal mucosa can be injured by a numberof inhalants. In this study, F344/N male rats were exposed tofiltered air or hyperoxia (85 or 87% oxygen), 24 hr/day, 7 days/week,for 1 (acute exposure) or 11 (chronic exposure) weeks. Therewere distinct differences between the different epithelial regionsexamined in replicative and morphologic responses as well asaltered enzyme activities in response to oxygen exposure. Neitheracute nor chronic hyperoxic exposure caused degenerative, necrotizing,or inflammatory changes in any of the nasal epithelial examined.Hyperoxia-induced hypertrophy, but not hyperplasia, of the non-ciliatedoiboidal (NCC) epithelium occurred after both acute and chronicexposure. Cell replication was increased in portions of theNCC and respiratory epithelia after acute hyperoxia exposure.There were significant increases, compared to controls, in thespecific activity of glucose-6-phosphate dehydrogenase in thenasal turbinates, maxilloturbinates, and lateral wall epithelium(NCC epithelium), the nasal septum (respiratory epithelium),and the ethmoturbinates (olfactory epithelium), and in the specificactivity of glutathione peroxidase in the NCC epithelium andethmoturbinates after acute hyperoxia exposure. The specificactivity of cytochrome P450-dependent monooxy-genase-catalyzedO-deethylation of 3-cyano-7-ethoxycoumarin was significantlydecreased, compared to controls, in the NCC epithelium. Theseresults suggest that hyperoxia exposure induces morphologicand biochemical alterations in nasal epithelia which appearto be protective responses of certain cell types to hyperoxia.