Medline ® Abstract for Reference 34

of 'Reactive airways dysfunction syndrome and irritant-induced asthma'

34
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Effects of dexamethasone on functional and pathological changes in rat bronchi caused by high acute exposure to chlorine.
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Demnati R, Fraser R, Martin JG, Plaa G, Malo JL
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Toxicol Sci. 1998;45(2):242.
 
We assessed the effects of dexamethasone on functional and histological changes after acute exposure to a high level of chlorine gas in an animal model of reactive airways dysfunction syndrome (RADS). Sprague-Dawley male rats were exposed to 1500 ppm of chlorine for 5 min and treated with either dexamethasone (dex; 300 micrograms/kg/day) or saline intraperitoneally for 7 days. Lung resistance (RL), airway responsiveness to inhaled methacholine (MCh), airway wall morphometric measurements, and bronchoalveolar lavage (BAL) cells were assessed over a 2-week period after exposure. Dex administration significantly attenuated both chlorine-induced increased RL and chlorine-induced increased responsiveness to methacholine compared with saline: -2.7 +/- 6.8% vs 102.3 +/- 36.6% change from baseline RL (P<0.01) and 2.5 +/- 0.6 mg/ml vs 1.2 +/- 0.7 mg/ml in the MCh concentration required to double the RL from baseline (P<0.01). There was a tendency, albeit nonsignificant, for improvement in some indices of epithelial injury. Dex significantly attenuated the postexposure neutrophilic cellular response in BAL 1 day after exposure (15.8 +/- 4.9% neutrophils in the dex group vs 49.8 +/- 2.7% neutrophils in the saline group) (P<or = 0.001). Our results show that dex administration helps maintain pulmonary function, reduces BAL inflammatory cell number, and tends to improve some morphometric airway wall structure parameters in rats exposed to chlorine.
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Department of Chest Medicine, Hôpital du Sacré-Coeur, Montreal, Quebec, Canada.
PMID