Antigen-Induced Bronchial Anaphylaxis in Actively Sensitized SD Rats.

We studied the effects of anti-asthmatic and anti-inflammatory drugs on antigen-induced bronchial anaphylactic reactions (BAR) in Sprague Dawley (SD) rats immunized with ovalbumin (OA) and alum. The animals were treated locally (intratracheal instillation (i.t,) or by aerosol) with terbutaline (TERB), disodium cromoglycate (DSCG), theophylline (THEO), the xanthine derivative 3,7-dihydro-1,8-dimethyl-3-phenyl-1H- purine-2,6-dione (D4026), budesonide (BUD) or dexamethasone (DEX) at various times before intravenous (i.v.) challenge with OA. The BAR was elicited by giving a low dose of OA. When the response to that challenge had leveled an additional high dose of antigen was given. Previous work had shown that TERB, DSCG, and D4026 given systemically (i.v.) at a suboptimal dose, had a better inhibitory efficacy when the animals were challenged with a low antigen dose late (6 weeks) than when challenged early (2-3 weeks) after immunization. We show here that such a difference in efficacy is not recorded after local treatment. Moreover, each of the drugs inhibited BAR to the same extent after i.t, as after i.v- treatment. Potent drugs like TERB and D4026 seemed to show similar efficacy when given either i.t. or by aerosol, whereas less potent drugs like DSCG and THEO were less effective when given by aerosol. In a previous study, we showed that the inhibitory capacity of glucocorticoids (GCS) on the BAR did not vary with sensitization conditions of the rats, BVD and DEX showed the same inhibitory capacity after intraperitoneal (i.p.) treatment as after i.t. treatment. In the present study, DEX showed increased whereas BUD showed decreased inhibitory capacity when given by aerosol 18-24h before challenge. The duration of the anti-anaphylactic activity after inhalation was longer for DEX than for BUD. [ABSTRACT FROM AUTHOR]