[Dynamic changes in airway hyperresponsiveness as a result of allergen and therapeutic effects of budesonide in rats].

Objective: To investigate the dynamic changes in airway hyperresponsiveness (AHR) in allergen-induced asthma in rats and the effects of budesonide.

Methods: Among 36 BALB/c female mice, 6 were randomized as negative control group (group C), the remaining mice were challenged with ovalbumin (OVA) to reproduce asthma. Kinetics of airway AHR of OVA-induced asthmatic mice was carried out as follows: on day 15, 18, 21 and 25 (A1, A2, A3, A4 groups), 6 mice were randomly chosen and sacrificed after measurement of airway AHR to investigate tidal volume (V(T)), airway resistance of expiring phase (R(A)), compliance of thorax and lung (C(T-L)) with different doses of methacholine chloride (MCH). In group B 6 mice were randomly chosen and treated with 1 mg budesonide aerosol once per day from day 15 to 17, then sacrificed on day 18. Their physiological and pathological changes were determined similarly to those of A2 group.

Results: (1) The increase of R(A) in group A1, A2 and A3 were significantly higher than that in group C when MCH reached the dose of 200 ng/g. (2) The decrease of C(T-L) in group A1 and A2 was significant with 100 ng/g and 200 ng/g MCH. (3) The value of V(T) markedly decreased in group A2 with 100 ng/g MCH and in all asthma model groups with 200 ng/g MCH than that in group C. (4) There was an eosinophil-dominant inflammatory infiltration in the asthma lungs, and the degree of infiltration peaked on day 15, and then alleviated afterwards. (5) With the dose of 200 ng/g MCH, the increase of R(A) in group B was significantly alleviated when compared with that in group A2, but there was no significant difference between group B and C. With the dose of 100 and 200 ng/g MCH, the decrease of C(T-L) in group B was significantly less marked compared with that in group A2 but there was no significant difference between group B and group C; the decrease of V(T) in group B was significantly lessened in degree when compared with that in group A2, while there was no statistical difference between group B and group C. The infiltration of inflammatory cells was obviously alleviated and the repair of airway epithelium was better in budesonide group.

Conclusion: (1) Airway hyperresponsiveness increases greatly in mice challenged and sensitized with OVA, and it lasts for about 7 days and then declines afterwards. (2) Budesonide aerosol could effectively alleviate the eosinophil dominant inflammatory response and decrease AHR in the murine asthma model.