Alteration of the angiotensin cascade by schistosome ova

In schistosomiasis mansoni, the parasite ova lodge in the microvasculature of organs and induce granulomas. It is assumed that factors derived from the ova activate circulating mediators that help initiate the inflammation. Components of the angiotensin system are in plasma and may have a role in inflammation. Therefore, whether ova could alter plasma angiotensin metabolism was determined. Incubation of 1 ml of plasma with up to 1,000 ova increased plasma AII (angiotensin II) concentration as measured by radioimmunoassay. HPLC analysis of [125I]AI (angiotensin I) metabolism in plasma suggested that ova can increase the conversion of AI to AII. Ova did not alter plasma angiotensin-converting enzyme activity. The ova themselves did not contain or release components of the angiotensin system during culture. It is concluded that interaction of ova with plasma can affect the angiotensin cascade.