Method for measuring endogenous 3-O-methyldopa in urine and plasma.
The present report describes a method using column liquid chromatography with electrochemical detection for assaying concentrations of 3-O-methyldopa in urine and plasma. The technique combines a one-step sample preparation scheme with post-column flow-through electrodes in series, allowing adequate chromatographic separation of 3-O-methyldopa from other endogenous substances in urine. The validity of the method was confirmed by markedly decreased urinary 3-O-methyldopa levels after administration of an inhibitor of catechol-O-methyltransferase to rats, radioactivity in chromatographic fractions corresponding to 3-O-methyldopa in urine of rats undergoing infusion of [3H]-L-DOPA, and correlations between excretion rates of 3-O-methyldopa and catechols in humans. In healthy humans, urinary excretion of 3-O-methyldopa averaged 974 +/- 707 (S.D.) nmol per day, and plasma levels of 3-O-methyldopa averaged 89 +/- 32 nmol/l. The method should be useful in studies about the metabolism of endogenous and exogenous DOPA.
Armando
I
I
Clinical Neuroscience Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Grossman
E
E
Hoffman
A
A
Goldstein
D S
DS
D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods*; D004563:Electrochemistry; D006801:Humans; D051381:Rats; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000097:blood / Q000652:urine
D014443:Tyrosine; C008404:3-methoxytyrosine