Angiotensin--forming enzyme active at the physiological Ph in the brain of normal and nephrectomized rats

Enzymatic activity generating angiotensin at pH 5.5 and 7.2 has been detected in different areas of the central nervous system (CNS) of the rat. Control animals and those subjected to bilateral nephrectomy 48 h before the experiment (Nx) were analyzed. The different areas of the CNS were studied by the incubation of tissue homogenates in the presence (enzyme concentration) or not (enzyme activity) of an excess of added angiotensinogen. Concentration was determined by incubation at pH 7.2 and 5.5 while activity was evaluated only at pH 7.2. The enzymatic renin-like concentration at both pHs did not change after Nx thus showing they do not depend on plasma and vascular renin. On the other hand the activity of the enzyme showed a significant increase in the cerebral cortex and cerebellum after Nx suggesting an increased concentration of renin substrate and/or different concentrations of inhibitors or activators of the enzymatic system in those areas.