Angiotensin-converting enzyme is present in the subfornical organ and other circumventricular organs of the rat.

Angiotensin-converting enzyme (ACE, kininase II, EC 3.4.15.1) activity was measured by a radiochemical assay in isolated circumventricular organs of the rat. ACE activity was unevenly distributed, with a 100-fold difference between the lowest (subcommisural) and the highest (subfornical organ) activities. Our results suggest that angiotensin II could be locally formed in circumventricular organs and especially in the subfornical organ. The high angiotensin-converting enzyme activity in the subfornical organ could indicate a physiological role of endogenous angiotensin II in this structure.