High degree of conversion of angiotensin I to angiotensin II in the mesenteric circulation of the isolated perfused terminal ileum of the cat.

Conversion of AI to AII has been studied in the mesenteric circulation of the isolated perfused cat terminal ileum. Infusion of AI through the mesenteric circulation induced a significantly potentiated response when the venous return was superfused over the rat colon and the rabbit aortic strip. Addition of converting-enzyme inhibitor, SQ 20881 to the perfusion medium competitively prevented the potentiation of AI on the assay organs without altering its direct effects. The percent conversion of AI to AII was found to be 68 in the mesenteric circulation. In contrast, infusion of AII through the mesenteric circulation has lost about 40% of its biological activity as measured on the same assay organs. SQ 20881 abolished the inactivation of AII in the mesenteric circulation. It is concluded that the mesenteric circulation of the isolated perfused cat terminal ileum is one of the major conversion areas of AI to AII. SQ 20881 prevented the conversion of AI to AII as well as abolishing the inhibition of AII passing through the mesenteric circulation.