The excretion of dopamine and dopamine metabolites in Parkinson's disease and the effect of diet thereon.

Abstract

Abstract Excretion rates of free and conjugated dopamine and of its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, were determined in a group of 34 patients with Parkinson's disease and a group of 20 controls. Over a period of 6 consecutive days, 24 hour urine specimens were collected from each person. All persons received an unrestricted mixed diet for the first period of 3 days and an infant formula preparation (Lactum, Mead Johnson Laboratories, Evansville, Ind.) for the second period of 3 days. Parkinsonian patients consistently excreted less free dopamine than the control persons, a difference which persisted during the milk diet. No difference was found in the excretion of conjugated dopamine when the patients and the male controls were compared. The excretion of homovanillic and 3,4-dihydroxyphenylacetic acids tended to be slightly lower in the patients but the difference was not consistently significant. Replacement of the mixed diet by the milk diet resulted in a decrease in the excretion of all the compounds estimated in both patients and controls, and this effect was significant with few exceptions. It is suggested that the reduction in the excretion of free dopamine in the patients is connected with a prolonged history of medication and that the effect of the diet is mainly due to a reduction of protein intake.