Angiotensin-converting enzyme activity of the brain and the aorta in experimental hypertensive rats

Angiotensin-converting enzyme activity in six areas of the brain (cerebral cortex, midbrain, thalamus, hypothalamus, striatum, and cerebellum) and subcellular fractions of the aorta (homogenate, mitochondria, microsomes, and supernatant) was determined in both normotensive and renal hypertensive rats [Goldblatt one-clip, one-kidney (1-c, 1-k) and one-clip, two-kidney (1-c, 2-k) hypertensive, and two-clip, two-kidney (2-c, 2-k) hypertensive rats]. Converting-enzyme activity was relatively high in the thalamus and relatively low in the cerebellum in normotensive and renal hypertensive rats. The enzyme activity in the hypothalamus of Goldblatt 1-c, 2-k rats was significantly higher than that of normotensive and other renal hypertensive rats. However, there was no significant difference in the enzyme activity in each brain area among normotensive, Goldblatt 1-c, 1-k hypertensive and 2-c, 2-k hypertensive rats. The enzyme activity of the supernatant from aortic subcellular fractions was extremely high in normotensive and renal hypertensive rats. However, the enzyme activity in all aortic fractions from Goldblatt 1-c, 2-k rats was significantly higher than that of normotensive and other renal hypertensive rats. There was no significant difference in the enzyme activity among normotensive, Goldblatt 1-c, 1-k hypertensive and 2-c, 2-k hypertensive rats. Therefore, it is likely that increased angiotensin-converting enzyme activity in the brain and the aorta may play a role in the initiation or the maintenance of hypertension in Goldblatt 1-c, 2-k hypertensive rats.