A Quantitative Study of Ciliary Injury in the Small Airways of Mice: The Effects of Nitrogen Dioxide

Abstract

The frequency and types of abnormal cilia prior to and following nitrogen dioxide (NO₂) exposure in the small airways of an inbred strain of mice was quantitated by transmission electron microscopy. Age-matched male and female mice were exposed ta 20 ppm NO₂ for 28 days. In both sexes, exposures to NO₂ resulted in a significant increase (P < 0.01) in abnormal cilia characterized by (1) decreased number of ciliary structures on cell surface, (2) focal swelling of the cytoplasmic matrix of the ciliary shaft, and (3) occasional compound cilium. The basal bodies of the ciliated cells from which atypical cilia arose appeared normal. In mice killed 30 days after termination of NO₂ exposure, the ciliary morphology returned to normal and the incidence of abnormal cilia decreased to levels observed in controls. These observations indicate that subacute exposure to NO₂ causes injury to the ciliary shaft; these changes are reversible within 30 days following removal from NO₂.