Inhibitory Effect of N‐(3′, 4′‐dimethoxycinnamoyl) Anthranilic Acid (N‐5′) on SRS‐A Mediated Bronchoconstriction in the Guinea Pig in Vivo

Slow-reacting substance of anaphylaxis (SRS-A) is an important factor mediating bronchoconstriction in asthma. We developed a guinea pig model for SRS-A-mediated bronchoconstriction induced by antigen inhalation. Using this model, we investigated the effect of N-(3', 4'-dimethoxycinnamoyl) anthranilic acid (N-5'), a new anti-allergic drug, on the bronchoconstriction. FPL 55712 inhibited most of the bronchoconstriction induced by antigen inhalation. N-5' inhibited the antigen-induced bronchoconstriction in a dose-dependent fashion. Intraperitoneal administration of 200 mg/kg N-5' was effective for 40 min after antigen inhalation, while the effect of 60 mg/kg lasted only 7 min. On the other hand, 200 mg/kg N-5' showed no inhibitory effect on the bronchoconstriction caused by direct inhalation of leukotriene C4, a component of SRS-A. These findings indicate that one of the anti-allergic actions of N-5' is due to inhibition of synthesis and/or release of SRS-A.