The association between inflammatory cell influx, cell activation status and change of airway responsiveness to acetylcholine (ACh) after daily inhalation of ovalbumin (OA) in sensitized guinea-pigs was investigated. Starting 3 weeks after sensitization (OA at 50 mg/kg s.c.+i.p.) guinea-pigs were exposed daily to 2% OA (10 min; under cover of 0.5 mg/kg mepyramine i.p. 15 min before OA) for 2 weeks. Concentration-response curves (CRCs) for inhaled ACh were performed 24 h after the last OA-challenge and 24 h after another single OA-inhalation 1 week later. CRCs for inhaled ACh were neither affected 24 h after the last OA challenge (daily for two weeks) nor 24 h after another OA-inhalation one week later. In contrast, bronchoalveolar lavage (BAL) from repeatedly OA- sensitized/-challenged guinea-pigs immediately after the last CRC showed a significant increase of total cell count by about tenfold and increases in eosinophils by about 20-fold, neutrophils by 30-fold, macrophages by about fivefold and lymphocytes by about tenfold (P < 0.05, multiple Wilcoxon-test). In contrast, markers of cell activation (EPO, MPO) were significantly decreased (P < 0.05). Methylprednisolone almost completely prevented these changes in increased cell numbers and decreased cell activation (vs OA contr., P < 0.05). The lack of increased airway hyperresponsiveness despite a massive inflammatory cell influx suggests other factors controlling airway responsiveness than inflammation.

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