It has been suggested that epithelium destruction, mucus secretion, edema and bronchoconstriction may play a role in asthma pathogenesis. Additionally, histamine, serotonine, leukotrienes and other mediators are released and free oxygen radicals are produced during bronchoconstriction. We studied the role of antioxidants on the treatment of asthma by testing a-tocopherol (vitamin E; 5, 25, 50 and 100 mg/kg/day i.p.), a scavenger of oxygen radicals, on male Guinea pigs. The animals were sensitized by injecting ovalbumin. After sensitization, isolated tracheal preparations were studied in vitro. The effects of carbachol 10(-4) M, ovalbumin 10(-3) M and vitamin E (10(-5) M, 10(-4) M, 10(-3) M concentrations) were evaluated in an isolated organ bath. It was observed that alpha-tocopherol reduced the contractile effects of ovalbumin and carbachol. The 5, 25 and 50 mg/kg/day doses of vitamin E were injected intraperitoneally to Guinea pigs that were sensitized with ovalbumin. We observed significant differences between the contractile responses to carbachol and vitamin E with carbachol. These treatments significantly reduced the contractility of tracheal preparations (p < 0.001). There was no significant difference with the 100 mg/kg/day i.p. dose of vitamin E in the contractile response to carbachol E (p > 0.05). The upper part of the tracheal preparations was the most sensitive region to the contractile effect of 10(-3) M ovalbumin in all groups (p < 0.001). The contractile response to 10(-3) M ovalbumin was reduced by 25 and 50 mg/kg/day doses of vitamin E (p < 0.001). (C) 2003 Prous Science. All rights reserved.