Induction of zymosan-air-pouch inflammation in rats and its characterization with reference to the effects of anticomplementary and anti-inflammatory agents.

Induction of an experimental inflammation of the air-pouch type with the aid of zymosan (known to activate the alternative pathway of the complement system) was carried out in an attempt to induce a reproducible inflammatory model suitable for quantitative studies. Rats were injected subcutaneously with 8 ml of air on the dorsal surface to make an air-pouch, followed 24h later by 4 ml of 1.6% (w/v) zymosan suspension. This induced inflammatory responses. Treatment with zymosan suspension provoked exudation of fluid, accumulation of polymorphnuclear leukocytes (PMN) in the pouch and the development of granulation tissue as a wall of the pouch. Approximately half of the PMN in the pouch formed a characteristic layer of aggregated cells sticking onto the inner surface of the pouch wall. They were counted after being completely disaggregated by means of incubation with trypsin. In preliminary experiments with potential anti-inflammatory drugs, local application of a novel anti-complementary agent, K-76COONa, inhibited leukocyte accumulation in the pouch, whereas the potent anti-inflammatory agent, dexamethasone, was ineffective. By contrast, exudation of the pouch fluid was effectively inhibited by dexamethasone but not by K-76COONa.