Angiotensin II Concentration in Cerebrospinal Fluid after Intraventricular Injection of Angiotensinogen or Renin*

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Abstract
To determine if the brain enzyme which has renin-like activity in vitro can form angiotensin in vivo, angiotensin II concentration in cerebrospinal fluid (CSF) was measured before and at various intervals after injection of partially purified renin substrate (angiotensinogen) into the 3rd cerebral ventricle of anesthetized dogs. The injection increased CSF angiotensinogen concentration 3-fold, but CSF angiotensin II concentration, which was undetectable (< 6.25 fmol/ml) before injection, did not change. Arterial blood pressure was also unchanged after the injection. Both CSF angiotensin II concentration and arterial pressure increased after an intraventricular injection of renin. Angiotensin II is formed centrally after administration of exogenous renin but not after injection of angiotensinogen. Renin activity in the brain in vivo was not demonstrated.