Enhancement of inflammatory reactions in a non-immunological air pouch model in rats

In a carboxymethyl cellulose (CMC) air pouch inflammation model, accumulation of exudate decreased at a relatively rapid rate and almost disappeared 3 days after a 2% CMC injection into the preformed air pouch. After a second injection of 2% CMC solution into the 1-day-old CMC pouch on the day following the first CMC injection, the decrease in rate of exudate was similar to the change seen after the first CMC injection. In another group of rats, 3 days after the first CMC injection when inflammation had subsided, a second injection of 2% CMC solution into the 3-day-old CMC pouch resulted in a marked increase of exudate accumulation, inflammatory cell infiltration and vascular permeability. Histologically, large numbers of macrophages accumulated in the 3-day-old CMC pouch and fibroblast proliferation and newly formed blood vessels were also visible. The enhanced exudative reaction was significantly inhibited by dexamethasone but not by indomethacin. These results indicate that the enhanced inflammatory reactions appear to be closely correlated with the increase of reactivity at the site of inflammation and the exudative reaction was not mediated by cyclo-oxygenase products.