[Allergen-induced late bronchoconstriction and airway hyperresponsiveness in guinea pigs].

Allergen-induced bronchoconstrictive responses were examined in a guinea pig model actively sensitized by the inhalation of aerosolized ovalbumin (OA), which showed reproducible late bronchial responses (LBR). OA-challenge was performed under cover of mepyramine through the inhaled route in spontaneous breathing without anesthesia. The respiratory resistance (Rrs) was measured by the oscillation method for 96 h after OA challenge. All of the 22 guinea pigs displayed immediate bronchial responses (IBR), followed by 2 or 3 phase LBR that peaked at 6-8 h and 24 h after OA challenge. Examination of bronchoalveolar lavage fluid (BALF) revealed a significant increase in neutrophils at 1 h (p less than 0.01) and eosinophils at 7 h and 96 h (each p less than 0.01) after OA challenge. OA-challenge induced airway hyperresponsiveness to histamine (p less than 0.01) at 96 h that was associated with a significant increase in eosinophils (p less than 0.01) in BALF compared with lavages at 7 h. Intravenous administration of 1% OA induced a significant increase of leukotriene (LT)B4, C4, D4 in tracheal lavage fluids at IBR phase in each control (p less than 0.01). The increases of Rrs in LBR were inhibited almost completely by the pretreatment of KC-404, which is reported to have antagonistic action against LTC4/D4. These results suggest that allergen-induced late broncho-constrictions accompanied by airway hyperresponsiveness in guinea pigs are associated with the extensive infiltration into the airway lumen of inflammatory cells, and are concerned with the release of LTs. We also suggest that this LBR guinea pig model is useful in studying the mechanisms of the occurrence of LAR in humans, and in evaluating the action of anti-allergic drugs in LAR.