Induction of an experimental passive anaphylaxis of the air-pouch type, passive air-pouch anaphylaxis, was carried out in an attempt to induce a reproducible anaphylaxis model suitable for quantitative studies. Rats were injected subcutaneously with 10 ml of air into the dorsal skin to make an air-pouch and with 2 ml of antiserum at an appropriate dilution for passive sensitization, and then 5 ml of air was removed. The challenge with 5 ml of antigen solution into the air-pouch 48 h later provoked mast cell degranulation and increased vascular permeability induced by released histamine. Treatment with monovalent hapten prior to the antigen challenge almost completely inhibited histamine release and plasma exudation to levels similar to those in the nonsensitized group. In this model, mast cell-dependent late-phase allergic reaction, such as leukocyte migration or the increase of plasma exudation following mast cell degranulation, was not observed.

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 μg/ml, but at 50 μg/ml it suppressed not only plasma exudation but also histamine release. Dexamethasone suppressed plasma exudation dose dependently without inhibiting histamine release significantly. A β-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.