Passive air-pouch anaphylaxis in rats. II. Pharmacological characterization

The effects of some antiallergic agents on passive air-pouch anaphylaxis (PAPA) in the dorsal skin of rats were investigated by measuring plasma exudation and histamine content in the pouch fluid. Antiallergic agents, disodium cromoglycate (DSCG), tranilast and ketotifen, dose dependently inhibited both plasma exudation and histamine release, except that ketotifen showed a dose-unrelated inhibition of histamine release. An antihistamine, pyrilamine, suppressed plasma exudation without affecting histamine release. A cyclooxygenase inhibitor, indomethacin, and a 5-lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), showed no significant effect. A slow-reacting substance of anaphylaxis antagonist, FPL55712, exerted no effect at 0.3 and 3.0 micrograms/ml, but at 50 micrograms/ml it suppressed not only plasma exudation but also histamine release. Dexamethasone suppressed plasma exudation dose dependently without inhibiting histamine release significantly. A beta-stimulant, isoproterenol, and prostaglandin E2 also exerted significant inhibitory effects on plasma exudation but not on histamine release at 1 mg/ml. Theophylline inhibited both plasma exudation and histamine release. These observations indicate that PAPA is useful for studying antiallergic agents.