A. Boulton, G. Marjerrison
Mar 10, 1972
Citations
0
Influential Citations
41
Citations
Quality indicators
Journal
Nature
Abstract
P-TYRAMINE is a normal constituent of human urine1–8, excreted in free and conjugated forms2,4,8. The level of excretion is quantitatively evaluated by separating the phenolicamine fraction (isolated by absorption onto a ‘Biorad AG50W-X2’ column1) overnight in isopropylether: methylethyl ketone : acetic acid : water 9 : 1 : 5 : 5 (v/v) on a Whatman No. 2 paper strip followed by conversion to the 1-nitroso-2-naphthol fluorophore and photodensitometric evaluation9. This procedure has shown that approximately 60% of Parkinson patients excrete more unconjugated urinary p-tyramine than does a control group4,8,10. Food precursors rich in p-tyramine were shown to increase the levels of conjugated p-tyramine and its principal acid metabolite p-hydroxyphenylacetic acid (both free and bound forms)4,8,11. These three metabolites increased so as to account almost stoichometrically for the ingested amine4. Sterilization of the intestinal tract with neomycin and succinyl sulphathiazole in a patient with Parkinson's disease caused a considerable increase in both free and bound forms of both amine and acid4. These findings suggest that a proportion of conjugated p-tyramine and total p-hydroxyphenylacetic acid arise from exogenous sources whereas most of the free urinary p-tyramine is endogenous8. This observation is confirmed in the work of several others5–7 although Perry et al.7 interpret their findings differently. A more convincing demonstration of the validity of our hypothesis followed from an assessment of the urinary free and bound p-tyramine and p-hydroxyphenylacetic acid excreted in urine after oral and intravenous administration of p-hydroxyphenyl(ethylamine-2-14C)-hydrochloride. In a control population only a tiny proportion of ingested p-tyramine, even when substantially supplemented with cold amine, is excreted in the urine in the free form (Table 1). After intravenous injection, however, a variable but significant amount of unconjugated amine is excreted.