allopurinol and Bronchial-Hyperreactivity

We elucidated the implication of oxygen radicals on airway hyperresponsiveness after ovalbumin (OA) challenge in guinea pigs. Ten days OA exposure increased airway responsiveness, i.e., a significant decrease in log [acetylcholine (Ach) PC200] (2.445 +/- 0.227) was observed compared with the control group (3.398 +/- 0.269). After OA exposure, the number of beta-adrenoceptors decreased by 38%, and adenylate cyclase activity decreased by 36% (isoproterenol stimulated) and 28% (basal). Significant increases in xanthine oxidase activities in lung tissue, bronchoalveolar lavage fluid (BALF), and serum were observed after the tenth OA exposure (49.1 +/- 11.7 mU/g tissue, 12.6 +/- 3.16 mU/ml, and 11.5 +/- 2.66 mU/ml, respectively) compared with those in the control group (7.35 +/- 6.48 mU/g tissue, 2.85 +/- 1.17 mU/ml, and 3.51 +/- 1.15 mU/ml, respectively). Administration of long-acting superoxide dismutase (SOD) (5,000 U/kg twice a day intraperitoneally) or gamma-glutamylcysteine ethyl ester (gamma-GCE) (10 mg/kg, twice a day, intraperitoneally), a prodrug of glutathione, maintained log [Ach PC200] (3.248 +/- 0.415 and 3.298 +/- 0.246, respectively) in spite of 10 days OA exposure. Decreases in the number of beta-adrenoceptors and adenylate cyclase activity were prevented by long-acting SOD or gamma-GCE. In contrast, long-acting SOD or gamma-GCE inhibited significantly, but not completely, the elevation of xanthine oxidase activities. These results support suggestions that oxygen radicals might be involved in the underlying mechanism of airway hyperresponsiveness after OA challenge in guinea pigs.

Topics: Adenylyl Cyclases; Animals; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Delayed-Action Preparations; Dipeptides; Guinea Pigs; Immunization; Lung; Male; Ovalbumin; Oxygen; Polyethylene Glycols; Receptors, Adrenergic, beta; Superoxide Dismutase; Time Factors; Xanthine Oxidase

The role of oxygen radicals in causing ozone-induced airway hyperresponsiveness in dogs was examined by pretreating dogs with allopurinol and/or deferoxamine mesylate (desferal), which are inhibitors of oxygen radical generation, before ozone inhalation. Acetylcholine airway responsiveness was measured before and after either air or ozone inhalation (3 ppm for 20 min) on 5 experimental days separated by at least 2 wk. On each day, the dogs were pretreated intravenously with allopurinol (50 mg/kg) followed by inhaled desferal (1,000 mg inhalation) or with allopurinol followed by the diluent for desferal or with the diluent for allopurinol and desferal or with both diluents. The effect of ozone on acetylcholine airway responsiveness was expressed as the differences in the log-transformed preozone-postozone acetylcholine provocative concentrations. When dogs received both diluents or either treatment alone, ozone inhalation caused airway hyperresponsiveness. The mean log differences for the preozone-postozone acetylcholine provocative concentration were 0.804 (SEM, 0.17) for both diluents, 0.524 (SEM, 0.16) for allopurinol alone, and 0.407 (SEM, 0.22) for desferal alone. However, the combination of allopurinol and desferal significantly inhibited the development of ozone-induced airway hyperresponsiveness, the log difference being 0.195 (SEM, 0.11) (p less than 0.05), without inhibiting ozone-induced neutrophil influx into the airways. The results suggest that the production of oxygen radicals is important in the pathogenesis of ozone-induced airway hyperresponsiveness.

Topics: Acetylcholine; Allopurinol; Animals; Antioxidants; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Deferoxamine; Dogs; Free Radicals; Ozone; Premedication