Effect of a selective thromboxane A2 receptor antagonist BAY u3405 on antigen-, leukotriene C4- and leukotriene D4-induced bronchoconstriction in guinea pigs.

We studied the effect of a selective thromboxane (TX) A2 receptor antagonist BAY u3405 on prostanoid-, leukotriene (LT) C4, LTD4- and antigen-induced bronchoconstriction in nonanesthetized guinea pigs in vivo. Oral administration of BAY u3405 inhibited bronchoconstriction induced by inhaled TXA2 mimetic U46619, prostaglandin (PG) D2 and PGF2 alpha. BAY u3405 also decreased the bronchoconstriction induced by inhaled LTC4 and LTD4. Intraperitoneal administration of TXA2 synthetase inhibitor OKY-046 did not affect PGD2- and PGF2 alpha-induced bronchoconstriction, but attenuated LTC4- and LTD4-induced bronchoconstriction. BAY u3405 and OKY-046 decreased antigen-induced bronchoconstriction in actively sensitized guinea pigs. These results indicate that BAY u3405 not only inhibits TXA2-, PGD2- and PGF2 alpha-induced bronchoconstriction that is mediated through a TXA2 receptor but also decreases LTC4. LTD4- and antigen-induced bronchoconstriction which is mediated in part through TXA2 synthesis. These results suggest that BAY u3405 might be useful in controlling prostanoid-induced bronchoconstriction in asthma.