Normal plasma dopamine- β -hydroxylase in non-treated and treated Parkinson patients

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Abstract
Plasma dopamine-.beta.-hydroxylase activity (DBH) was estimated in 50 drug-free Parkinson patients, 30 of whom had never been treated, in 26 patients treated chronically with L-dopa, and in 44 controls. Of the drug-free patients, 22 were examined again after 2 wk treatment with L-dopa plus decarboxylase inhibitor. No differences were found among the groups and no change in the enzyme activity occurred after treatment, although urinary homovanillic acid increased 20-fold. Low DBH activities could not be attributed to the age of onset or duration of illness, main symptom, depression, autonomic disturbances or duration of drug treatment. The only difference was found in patients with dementia associated to their illness, who showed low enzyme activities.