Effects of ozone re-exposure on substance P (SP)-innervation in airways of postnatal rats.
Mulvey T; Satterfield BE; Frazer DG; Fedan JS; Dey RD
Am J Respir Crit Care Med 2001 Apr; 163(5)(2)(Suppl):A824
Airway infections or irritant exposures during early postnatal periods may contribute to the onset of asthma during childhood and may be associated with exposure during critical periods of postnatal lung growth. In previous studies, a possible critical period was identified during which there was heightened neural sensitivity to ozone (O3) occurring around postnatal day (PD) 4. The present study examines the effects of an initial O3 exposure at PD4 on airway SP innervation 24 hr after re-exposure on day PD28. Rats were exposed to 2 ppm O3 or filtered air (FA) for 1 hr as follows: control (FA), single O3 exposure at PD28, single O3, exposure at PD4, multiple O3 exposure at PD21 and PD28, and multiple O3, at PD4 and PD28. At PD29, 24 hr after the last exposure, lungs were removed, fixed, and prepared for SP immunocytochemistry. Extrapulmonary (EP) and intrapulmonary (IP) airways were dissected and SP nerve fiber density (NFD) for epithelium (e) and smooth muscle (SM) was determined by image analysis. SP NFD in the IP-SM increased twofold from about 0.7% in control to 1.4% in the group exposed to ozone at both PD4 and PD28. SP-NFD was not altered in IP-E or in the EP airways of other exposure groups. These findings suggest that an initial ozone exposure during a possible critical phase of postnatal airway growth (PD4) followed by a second irritant exposure at PD28 leads to altered airway innervation not observed after a single PD28 exposure.
Lung irritants; Sensitivity testing; Laboratory animals; Animals; Animal studies; Irritants; Lung; Lung disorders; Bronchial asthma; Exposure levels; Exposure assessment; Airway obstruction; Pulmonary system disorders; Respiratory system disorders
American Journal of Respiratory and Critical Care Medicine. Abstracts of the American Thoracic Society 2001 International Conference, May 18-23, 2001, San Francisco, California