Detection of granuloma-associated plasminogen activator in experimental murine schistosomiasis

Hypersensitivity granulomas induced by infection with Schistosoma mansoni were isolated from the livers of BALB/c mice after 7, 8, 10, and 12 weeks. The parasite egg-granulomas were sequentially extracted with a Tris-buffered saline (soluble fraction) and 2 M KSCN (bound fraction). Fibrinolytic enzyme activity measured with both synthetic substrates and fibrin plates demonstrated an elevated level of plasminogen activator activity in the bound fraction 7-8 weeks after infection when mature granulomas first began to appear, followed by a gradual decrease 10-12 weeks after infection. An electrophoretic enzymography technique revealed multiple molecular species of plasminogen activator at Mr = 95K, 74K, 60K, 45K, and 24K. The bands with Mr = 45K and 24K were found compatible with the electrophoretic pattern of macrophage-plasminogen activator. When the granulomas reached maximum size after 10 to 12 weeks, the plasminogen activator with 45K and 24K diminished, while plasminogen activator activity at Mr = 95K, 74K, and 60K remained unchanged suggesting the presence of both vascular and tissue types of plasminogen activators. There was no urokinase-type plasminogen activator detectable in granulomas at any time. In the soluble fraction no enzymatic activity was found, whereas regulating inhibitor activity for plasminogen activator was consistently detectable.