Isolated liver granulomas of murine Schistosoma mansoni contain components of the angiotensin system.

Angiotensin I (AI) and angiotensin II/III (AII/III) were detected by radioimmunoassay in homogenates of isolated liver granulomas from mice infected for 8 wk with Schistosoma mansoni. Angiotensin I converting enzyme (ACE) activity, which could be completely inhibited by captopril, a specific ACE inhibitor, was also present as determined by radioassay. Spontaneous angiotensin I-generating activity was detected in homogenates that received supplemental angiotensinogen (protein renin substrate). This activity was partly inhibited by pepstatin, an acid protease inhibitor, indicating the presence of angiotensinogenase(s). Trypsinization of homogenates resulted in some AI generation, which suggests that homogenates had AI precursor. Treatment of infected mice with MK421, another specific ACE inhibitor, decreased granuloma ACE activity and AII content and size. AII, and to a lesser extent AIII, inhibited mouse peritoneal macrophage migration in an in vitro assay. These data support the contention that components of the angiotensin system are in the granuloma and may serve a function in regulation of the inflammation.