Effect of Hoe 140 on bradykinin-induced bronchoconstriction in anesthetized guinea pigs.

We have investigated the efficacy of the novel, highly potent, and stable B2 bradykinin (BK) antagonist Hoe 140 against BK-induced bronchoconstriction in guinea pigs via whole body plethysmography and compared different routes of administration. Our results clearly demonstrate that Hoe 140 is highly potent at inhibiting bronchoconstriction induced by either intravenous (i.v.) or inhaled BK. Intravenous BK was strongly inhibited by i.v. Hoe 140 (ID50 13.4 pmol/kg), and less by aerosolized Hoe 140 (ID50 1.34 nmol/kg). Aerosolized BK (235 nmol/kg) was strongly inhibited by 0.1 nmol/kg of aerosolized Hoe 140 given 30 min before. Hoe 140 is the first BK antagonist to effectively inhibit the bronchoconstrictor effect of aerosolized BK. The equieffective i.v. dose of Hoe 140, however, as about 100-fold higher. From the discrepancy in efficacy of Hoe 140 against i.v. and aerosolized BK, it was concluded that i.v. BK has no direct effect on the lung, in contrast to inhaled BK. Moreover, the high potency of Hoe 140 in the guinea pig lung does not confirm the hypothesis of a B3 BK receptor. Based on its high potency and good tolerability, Hoe 140 is appropriate to evaluate the role of BK in human airway diseases.