Antiinflammatory activity of tissue plasminogen activator in the carrageenan rat footpad model

Exogenous plasminogen activators (PAs), such as streptokinase (SK) and tissue plasminogen activator (tPA), have been shown to significantly improve the mortality of patients with acute myocardial infarction. However, reperfusion of the myocardium is associated with neutrophil activation and infiltration into the infarct region. Plasminogen activators influence neutrophil function in vitro, but no data exists regarding the effect of exogenous PAs on inflammation in vivo. Therefore, we evaluated the effect of PAs on inflammation using the carrageenan-induced rat footpad inflammation model. The magnitude of carrageenan-induced inflammation was determined by water-displacement and neutrophil infiltration, following administration of either tPA or SK to Sprague-Dawley rats. tPA (12 mg/kg) inhibited carrageenan-induced inflammation (p < .01). In contrast, administration of SK (40,000 U/kg) enhanced inflammation. These results suggest that exogenous PAs influence the inflammatory process but specific PAs differ in their actions. Ultimately, these differences may influence the efficacy of these agents in the management of acute myocardial infarction and lead to further evaluation of tPA in other inflammatory diseases such as acute respiratory distress syndrome (ARDS) and rheumatoid arthritis (RA), in which neutrophil-mediated injury is likely.