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New pharmacological data on the bronchospasmolytic activity of bamifylline

Resistance to lung inflation and blood pressure were monitored together with biological and radioimmunological determination of circulating thromboxane A2 (TxA2) in anaesthetized guinea-pig. Bamifylline, a 2-benzyl-[4,5-d]-imidazopyrimidine derivative, and theophylline were compared for their antagonistic activity against the pulmonary effect of histamine (0.05 mumol/kg i.v.), leukotriene C4 (LTC4, 0.016 mumol/kg i.v.), platelet-activating factor (PAF, 0.0002 mumol/kg i.v.) and acetylcholine (0.1 mumol/kg i.v.). Bamifylline, as well as theophylline, showed a dose-dependent antagonistic activity against both bronchoconstriction and TxA2 generation induced by the above agonists. However, except for histamine where the two compounds were equiactive, bamifylline was 2 times more potent than theophylline. The maximal inhibitory activity was found against bronchoconstriction induced by PAF (ED50 = 6.5 mumol/kg i.v.) followed by histamine (ED50 = 9.5 mumol/kg i.v.), acetylcholine (ED50 = 24.3 mumol/kg i.v.) and LTC4 (ED50 = 31.6 mumol/kg i.v.). Bamifylline (3, 10, 30, 100 mumol/kg i.v.) and theophylline (3, 10, 30, 100 mumol/kg i.v.) protected guinea-pig from antigen-induced bronchoconstriction and TxA2 generation in ovalbumin actively sensitized animals. Also in this series of experiments bamifylline was more potent than theophylline, the ED50 being 9.3 mumol/kg i.v. and 22.9 mumol/kg i.v., respectively. These pharmacological data represent new support for the protecting effect of bamifylline against respiratory damage induced by well known anaphylaxis mediators

The PAF-acether receptor antagonist BN-52021 inhibits mediator release during guinea-pig active lung anaphylaxis

An anaphylactic reaction was induced with the specific antigen (1 mg Ovalbumin) in perfused lungs from actively sensitized guinea-pigs in order to evaluate the ability of the ginkgolide BN-52021 (0.4, 4, 40 micrograms/ml) to modulate the mediator release. The ginkgolide reduces in a dose dependent manner the release of histamine (22%, 45% and 75% of inhibition), TXB2 (77% of inhibition at the maximal dose used) and of SRS-A to a lower extent (only 33% at the higher dose). BN-52021 was still powerful in reducing histamine release induced by immunological reaction in indomethacin treated animals. In conclusion, the present "in-vitro" results confirm the beneficial activity of this ginkgolide, already demonstrated by the same Authors in "in-vivo" experiment, in anaphylactic reactions, and further substantiate the wider spectrum of action of the ginkgolide beside its specific PAF receptor antagonistic activity