Potential species dependency for the pulmonary antiallergic effects of aerosolized heparin

The inhibition of antigen aerosol-induced bronchoconstriction by heparin aerosol pretreatment has been demonstrated in conscious sheep. Therefore, we investigated the effect of heparin aerosol pretreatment on antigen aerosol-induced bronchoconstriction in anaesthetized and ventilated guinea-pigs. In one study all animals were pretreated with propranolol and indomethacin in order to produce a large bronchoconstriction, whereas in a second study this pretreatment was omitted in order to produce a smaller bronchoconstriction. In both studies aerosolized heparin failed to inhibit antigen aerosol-induced bronchoconstriction, whether delivered at 1, 10 and 100 mg/ml 10 min prior to antigen challenge or delivered at 50 mg/ml 60 min prior to antigen challenge. In contrast, salbutamol aerosol pretreatment (1 mg/ml, delivered 10 min prior to antigen challenge) produced a near-maximum inhibition of antigen aerosol-induced bronchoconstriction. These results suggest that the pulmonary antiallergic effects of aerosolized heparin are potentially species dependent.