Repeated exposure to low levels of sulfur dioxide (SO2) enhances the development of ovalbumin-induced asthmatic reactions in guinea pigs

Background Sulfur dioxide (SO 2 ) is one of the major air pollutants. It is known to aggravate asthma symptoms in human beings, but few studies have focused on the effects of SO 2 upon the development of bronchial asthma in animal models. Objective This study was undertaken to evaluate the role of SO 2 upon the development of ovalbumin (OA)-induced asthmatic reactions in guinea pigs. Methods Guinea pigs were divided into four groups: (1) OA-and SO 2 -exposed group (n = 12), (2) SO 2 -exposed group (n = 12), (3) OA-exposed group (n = 11), and (4) saline-exposed group (n = 7). Guinea pigs of the first and second groups were exposed to 0.1 ppm SO 2 for 5 hours a day on 5 consecutive days. Guinea pigs in the first and third groups inhaled 0.1% OA aerosols for 45 minutes a day on days 3, 4, and 5. One week after the sensitization procedure, all the guinea pigs underwent bronchial challenge with 1.0% OA aerosols, using unrestricted whole-body plethysmography. Bronchoalveolar lavage and histopathologic examination were performed 24 hours after the bronchial challenge. Results Increases in enhanced pause (P enh ), as an index of airway obstruction, after the bronchial challenge was significantly higher in OA-and SO 2 -exposed group (group 1) than the other groups ( P P Conclusions These results indicate that repeated exposure to low levels of sulfur dioxide may enhance the development of ovalbumin-induced asthmatic reactions in guinea pigs.