Cerebrospinal fluid levels of angiotensin-converting enzyme in Alzheimer's disease, Parkinson's disease and progressive supranuclear palsy.

Angiotensin-converting enzyme (ACE, E.C. 3.4.15.1) has been identified as a normal constituent of human cerebrospinal fluid (CSF). ACE activity in CSF from adult subjects without known neurologic disorder correlated positively (P = 0.002) with age between 50 and 90 years. Patients with moderate degrees of senile dementia of the Alzheimer's type and comparably demented patients with Parkinson's disease or progressive supranuclear palsy exhibited mean levels of ACE activity that were decreased 41, 27 and 53% respectively, compared to the mean level in an age and sex-matched group of neurologically intact individuals. These results raise the possibility that ACE activity in CSF may be an index of neuronal dysfunction in certain central neurodegenerative disorders.