Abstract
The effect of traxanox on SRS-A release was examined in vivo and compared with that of disodium cromoglycate (DSCG). Intravenous antigen challenge produced an intense anaphylactic bronchoconstriction that showed a peak time of 5 min in egg albumin-sensitized guinea pigs pretreated with three agents, mepyramine (2.5 mg/kg, i.v.), indomethacin (1 mg/kg, i.v.) and propranolol (0.05 mg/kg, i.v.). This bronchoconstriction was almost completely inhibited by additional pretreatment with an SRS-A antagonist, FPL 55712 (2.5 mg/kg, i.v.). A lipoxygenase inhibitor, BW755C (10 mg/kg, i.v.), also significantly inhibited this reaction. These results indicate that this anaphylactic bronchoconstriction is due to the release of endogenous SRS-A. In this model, traxanox (5 and 10 mg/kg, i.v.) showed a dose-related inhibition, but DSCG (10 mg/kg, i.v.) did not. FPL 55712 (1 mg/kg, i.v.) administered at the peak time of the bronchoconstriction caused a relaxation. Traxanox, on the other hand, failed to relax this reaction. In IgE-mediated rat passive peritoneal anaphylaxis (PPA), traxanox (0.01 ?? 10 μg/rat, i.p.) inhibited the release of SRS-A and histamine dose-dependently. This inhibitory effect was about 10 ?? 20 times as potent as that of DSCG. In addition, both traxanox (0.1 μg/rat, i.p.) and DSCG (1 μg/rat, i.p.) showed a synergistic effect in combination with isoproterenol (0.01 μg/rat, i.p.) and an additive effect with theophylline (100 μg/rat, i.p.) in inhibiting the release of SRS-A in rat PPA. These results suggest that traxanox inhibits the release of SRS-A in vivo, so that it may be clinically effective in treating patients with allergic bronchial asthma.
