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RESEARCH PRODUCT

Dissociation of airway responsiveness and bronchoalveolar lavage (BAL) cell composition in sensitized guinea-pigs after daily inhalation of ovalbumin

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Summary. The association between inflammatory cell influx, cell activation status and change of airway responsiveness to acelylcholine (ACh) after daily inhalation of ovalbumin (OA) in sensitized guinea–pigs was investigated. Starting 3 weeks after sensitization (OA at 50mg/kg s.c. + i.p.) guinea–pigs were exposed daily to 2% OA (10min: undercover of 0.5Smg/kg mepyramine i.p. 15min 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.