Antigen-induced bronchial anaphylaxis in actively sensitized SD rats. Effects of glucocorticoid treatment.

We examined the effects of glucocorticosteroids (GCS) on antigen-induced bronchial anaphylactic reactions (BAR) in SD rats immunized with ovalbumin (OA) and alum. The animals were treated with vehicle, budesonide (BUD), dexamethasone (DEX), or hydrocortisone (HC) at various times before intravenous (i.v.) antigen challenge. The drugs were administered either intraperitoneally (i.p.) or intratracheally (i.t.); the BAR was elicited by a low or by a high challenge dose of antigen. A BAR elicited by a low challenge dose of antigen was reduced in a dose-dependent way by all GCS after i.p. administration; at 1 mg/kg, BUD and DEX significantly reduced BAR and at 50 mg/kg all three of the examined compounds inhibited the BAR by 50% or more. For BUD, maximum effect was recorded when it was given 12 h before test. There was only a slight variation in the inhibitory effects of the GCS with immunization conditions of test animals. I.t. instillation of the drugs did not markedly increase their inhibitory capacity as compared to i.p. administration. BAR elicited by a high antigen dose was at best marginally affected by the GCS when given either i.p. or i.t. Thus, antigen-induced airway reactivity in rats can be reduced by GCS treatment provided that this is performed sufficiently long before the test and that the challenge dose of antigen is not too high.