Detection of granuloma-associated plasminogen activator in experimental murine schistosomiasis

Abstract

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 M r = 95K, 74K, 60K, 45K, and 24K. The bands with M r = 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 M r = 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.