Kk. Sheth et al., REVERSAL OF PERSISTENT POSTBRONCHIOLITIS AIRWAY ABNORMALITIES WITH DEXAMETHASONE IN RATS, Journal of applied physiology, 76(1), 1994, pp. 333-338
Viral bronchiolitis is a common disease that may result in persistent
airway abnormalities. Previous studies of neonatal bronchiolitis in ra
ts revealed chronic sequelae, including airway obstruction, airway hyp
erresponsiveness, increased production of airway eicosanoids, and incr
eased numbers of bronchiolar mast cells. To address the hypothesis tha
t postbronchiolitis airway obstruction is caused in part by reversible
processes, we tested whether obstruction could be reversed by a brief
course of high-dose corticosteroids. Neonatal Brown Norway rats (5 da
ys of age) were inoculated with parainfluenza type 1 virus or sterile
vehicle. At 8 wk of age, rats were treated with dexamethasone (1.4 mg.
kg(-1).day(-1) sc) or saline for 3 days and were evaluated for lung me
chanics, gas exchange, and lung inflammatory cells 1 day after the las
t injection. Dexamethasone normalized the chronic virus-induced airway
obstruction and reduced the numbers of bronchiolar mast cells and oth
er inflammatory cells. Resistance and dynamic compliance correlated si
gnificantly with bronchiolar mast cells but not with other airway infl
ammatory cell infiltrates. We conclude that the airway abnormalities t
hat persist in rats after recovery from neonatal bronchiolitis are ass
ociated with increased numbers of bronchiolar mast cells and are large
ly due to corticosteroid-sensitive mechanisms.