Pharmacological modulation of allergic inflammation in the rat airways andassociation with mast cell heterogeneity

Administration of ovalbumin by aerosol to sensitised rats produced a rapid (15 min) protein exudation in different airway tissues, as determined by Ev ans blue staining. This was associated with marked mast cell degranulation determined by histological examination, with there being no difference betw een mucosal and connective tissue mast cells. A 5-day administration regime n with compound 48/80 selectively depleted connective tissue mast cell (Pos itive to berberine staining) without modifying ovalbumin-induced plasma pro tein extravasation. Treatment of rats with dexamethasone (1 mg/kg, - 12 h) or nor-dihydroguaiaretic acid (30 mg/kg i.p., - 30 min) significantly reduc ed ovalbumin-induced protein extravasation and preserved mucosal mast cell morphology. Indomethacin (4 mg/kg i.v., - 30 min) exerted no effect on eith er parameter. In conclusion, we propose the mucosal mast cell as a target c ell responsible at least partly for the inhibitory actions of known anti-in flammatory drugs. We suggest an involvement of endogenous leukotriene(s), b ut not prostanoid(s), in mucosal mast cell activation/degranulation. (C) 20 01 Published by Elsevier Science B.V.