Tyrosine metabolism: urinary excretion studies in Parkinsonism.

Vanilmandelic, homogentisic and homovanillic acid excretions were studied in parkinsonian patients on and off L-dopa. Vanilmandelic acid excretions were quantitated both by gas-chromatographic and calorimetric 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 L-dopa, the increase is much smaller than that of free homovanillic acid. The latter consistently accounts for some 18-20~/~ of the administered I,-dopa dose. While vanilmandelic acid excretions even under the influence of L-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 L-dopa. No correlation was observed between the clinical status or response to L-dopa of the patients and their excretion of acidic urinary catabolites.