Tyrosine metabolism: Urinary excretion studies in parkinsonism

Abstract

Vanilmandelic, homogentisic and homovanillic acid excretions were studied in parkinsonian patients on and off -dopa.Vanilmandelic acid excretions were quantitated both by gas-chromatographic and colorimetric methods. A marked increase in the excretion of this acid was demonstrated in the parkinsonian patient as compared to controls. Although Vanilmandelic excretion rises under the influence of -dopa, the increase is much smaller than that of free homovanillic acid. The latter consistently accounts for some 18-20% of the administered -dopa dose. While vanilmandelic acid excretions even under the influence of -dopa correlate well with the patients' weight, no such correlation could be obtained with homovanillic acid.Homogentisic acid could not be detected in urine specimens of patients either on or off -dopa. No correlation was observed between the clinical status or response to -dopa of the patients and their excretion of acidic urinary catabolites.