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To elucidate the role of collagenase in tissue destruction in chronic inflammation (e.g., in rheumatoid arthritis), we established a novel air pouch model in rats. Ten ml of air was injected subcutaneously on the dorsa of F344 rats, and 24 hours thereafter, Freund's complete adjuvant was injected into the air pouch. A remarkably high activity of trypsin-activated collagenase was detected dose-dependently in the pouch fluid at 8 days after the challenge injection. Concomitantly with the increase of collagenase activity, the weight of granuloma formed in the pouch decreased, suggesting that collagenase participates in the resorption of granuloma tissues.

Endogenous phospholipase A2 (PLA2) specific activity (SA) (% hydrolysis/min/mg protein) in the rat pleural cavity, measured as the acyl-hydrolysis of [3H]-arachidonic acid E. coli substrate, was quantitated after induction of a reverse passive Arthus reaction (RPAR). PLA2 SA, derived when the rate of hydrolysis was linear (1-5 min), was 1.9, 1.4, 3.8 and 4.1% h/min/mg at 10 min, 2 h, 4 h and 24 h, respectively, after induction of the RPAR. This time course appeared to correlate with the influx of mononuclear inflammatory cells, although the effect of plasma leakage on changes in exudate PLA2 SA could not be determined. Oral administration of antiinflammatory drugs significantly inhibited pleural fluid exudation and inflammatory cell influx to varying degrees. However, whereas these drugs additionally reduced total exudate protein and PLA2, they had no effect on the concentration of either parameter, implying that pleural PLA2 may be passively linked to fluid and cell movement.

At 10 min, 2 h and 4 h after induction of a reverse passive Arthus reaction (RPAR) in the pleural cavity of rats, pleural exudate was collected and analyzed in vitro for phospholipase A2 (PLA2) acyl hydrolytic activity. Inasmuch as exudate PLA2 was inhibited by addition of EDTA, the acyl hydrolytic activity appeared calcium-dependent. However, addition of exogenous calcium to the exudate had only a minor effect on the activity. Maximum hydrolysis in all exudates was observed over a pH range of 6-9 with a neutral optimum. The 4 h exudate PLA2 activity was almost fully inhibited by para-bromophenacyl bromide (pBPB), whereas the acyl hydrolytic activity in the 10 min and 2 h exudates was reduced by 44% and 46%, respectively, by 200 microM pBPB. Although the PLA2 in the 4 h exudate displayed an increased sensitivity to high exogenous calcium concentrations and to pBPB inactivation, the basic properties of the exudate PLA2 at the three time points appeared similar.