Airway Inflammation and Responses in the Bronchial Asthma Model in Sprague-Dawley Rats Sensitized by Ovalbumin

Na, Moon Jun; Lee, Byoung Hoon; An, Chang Hyeok; Kim, Jae Yeol; Park, In Won; Choi, Byung Whui; Hue, Sung Ho

Abstract

BACKGROUND: To evaluate airway responses and inflammation to antigen in Sprague-Dawley rat asthma model, we examined airway responses, serial histologic changes of the lung, and the relationship between airway responses and airway inflammation after antigen airway challenge.
METHODS
Sprague-Dawley rats were sensitized with subcutaneous injection of 10 microgram ovalbumin(OA). Antigen airway challenges were done 14 ~16 days after sensitization and the sensitized rats were sacrificed 1h(AE), 6 ~8h(AL) and 1day(AD) after airway challenge, to examine the histologic changes of the lung. Airway responses were measured by body plethysmograph and recorded by enhanced pause(Penh) as an index of airway obstruction 6 ~8h after antigen challenges. Nonsensitized controls(10 rats) were also challenged with antigen and sacrificed 1 day later. Histopathologic examination of two trachea, large bronchi, small bronchi, and vessels was performed to evaluate the severity of inflammation and eosinophilic infiltration with H&E stain.
RESULTS
In 17 of 20 rats(85%) in both groups, we observed airway responses. Among them, an early response(ER) in 15 rats(75%), an dual response in 5(25%), and an late response(LR) only in 2 rats(10%) displayed. There were no significant differences in the severity of inflammation among the trachea, large bronchi, small bronchi and vessels in all groups after antigen challenge(p>0.05) and between early and late responders. The significant eosinophil infiltration was observed in 5 rats(50%) of AL(p<0.05) compared with in AE and controls. Also, eosinophil infiltration was observed in higher trend in LR(57.1%) compared to ER(40%)(p>0.05).
CONCLUSION
Sprague-Dawley rats sensitized with subcutaneous injection of OA showed a significant airway responses to antigen challenge. But antigen challenges caused a little eosinophil infiltration and no significant airway inflammation. Asthma model of Sprague-Dawley rats could be useful for antigen-induced airway responses, but this model has a limitation for the study of human asthma because of no significant pathologic change.