Effect of Three Novel K+ Channel Openers, Cromakalim, Pinacidil and Nicorandil on Allergic Reaction and Experimental Asthma.

The anti-allergic and anti-asthmatic activities of three potassium (K+) channel openers, cromakalim, pinacidil, and nicorandil, were investigated. 1) Forty-eight-hour homologous passive cutaneous anaphylaxis (PCA) in mice was not affected by cromakalim, pinacidil, or nicorandil. Ketotifen significantly inhibited the reaction. 2) Antigen-induced histamine release from sensitized guinea pig lung tissue was not affected by cromakalim, pinacidil or nicorandil (except for 10(-4) M nicorandil). Salbutamol inhibited the release of histamine. 3) Histamine, serotonin and LTC4-induced vasculitis in rat back skin was not affected by any of these three K+ channel openers. 4) Antigen-induced constriction of isolated sensitized guinea pig tracheal muscle was relaxed by each of the K+ channel openers. 5) Constrictions of isolated guinea pig tracheal muscle caused by high potassium, histamine, LTC4, or U-46619 were clearly relaxed by each of the three K+ channel openers. 6) Increases of airway resistance caused by histamine, LTD4, or U-46619 in guinea pigs in vivo were inhibited by administration of each of the three K+ channel openers. 7) Experimental asthma caused by the IgE antibody and antigen system in guinea pigs was inhibited by each of the three K+ channel openers.