Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 274, Issue 4, pp 404–409 | Cite as

Demethylation of l-3-methoxytyrosine in vivo

  • G. Bartholini
  • A. Pletscher


After administration of purified l-14C-3-methoxytyrosine (l-14C-3-MTO) to rats, the fractions of labelled amino acids, catecholamines and phenolcarboxylic acids of urine and brain have been separated by column chromatography. Prior to performing the quantitative determinations, the individual metabolites of each urinary fraction and of the cerebral catecholamine fraction were isolated by paper chromatography using different systems. Susbtantial amounts of 14C-3,4-dihydroxyphenylacetic acid (14C-DOPAC) as well as some 14C-3,4-dihydroxyphenylalanine (14C-DOPA) and traces of dopamine (DA) appeared in the urine. Furthermore, small amounts of 14C-DA and 14C-norepinephrine were found in the brain with two different chromatographic systems. The urinary excretion of 14C-DOPAC and 14C-DA was increased by pretreatment with dopacetamide, an inhibitor of catechol-3-O-methyl-transferase. A possible contamination of the l-14C-3-MTO with traces of l-14C-DOPA as a major source of the dihydroxylated metabolites has been ruled out. It is concluded that part of l-3-MTO undergoes demethylation in vivo and that the finding of DA in brain and urine after administration of l-3-MTO is not an artifact.

Key words

l-3-Methoxytyrosine Demethylation l-DOPA Dopamine 


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Copyright information

© Springer-Verlag 1972

Authors and Affiliations

  • G. Bartholini
    • 1
  • A. Pletscher
    • 1
  1. 1.Research DepartmentF. Hoffmann-La Roche & Co. LtdBaselSwitzerland

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