Angiotensin II forming activity of vascular endothelial and smooth muscle cells

To clarify the role of vascular endothelial cells (VEC) and smooth muscle cells (VSMC) in the generation of angiotensin (Ang) II, we measured the Ang II forming activity of these cells in culture using synthetic Ang I and tridecapeptide renin substrate (13RS). Angiotensin converting enzyme (ACE) activity was demonstrated in both types of cells, and the Ang I converting activity was highly sensitive to an ACE inhibitor. Both VEC and VSMC were able to generate Ang II from 13RS independently of ACE and renin. The activity was partially inhibited by chymostatin. It is suggested that Ang I could be converted to Ang II not only by VEC but also by VSMC. Both VEC and VSMC possess alternate Ang II forming pathways independent of ACE and renin.