Assessment of O-methylated catecholamine levels in plasma and urine for diagnosis of autonomic disorders.

Abstract

The term 'metanephrines' is used to indicate the two catechol 3-O-methylated metabolites of epinephrine (E) and norepinephrine (NE): metanephrine and normetanephrine (NMN). The corresponding 3-O-methylated metabolite of dopamine is usually referred to as 3-methoxytyramine rather than 3-methoxydopamine and is not generally considered a "metanephrine". O-Methylation occurs outside the sympathetic neuron and neuroeffector junction. Metanephrines are products of the enzyme catechol-O-methyltransferase (COMT). Subsequent conjugation with sulfate or deamination by monoamine oxidase (MAO) followed by reduction to vanilmandelic acid (VMA) facilitates urinary excretion. For the clinician, measurement of normetanephrine provides an index of norepinephrine released during sympathetic nervous system activity, whereas metanephrine concentration provides an indication of adrenal medullary metabolism of epinephrine prior to its discharge into the circulation. Plasma epinephrine concentration is the preferable index of adrenal medullary epinephrine discharge. Pheochromocytomas, with their protean clinical manifestations, may be diagnostic challenges, but assay of metanephrines, especially plasma metanephrine, can be particularly helpful in diagnosis. These COMT metabolites may also help in elucidation of still undiscovered genetic and acquired disorders of catecholamine metabolism.

• Authors: Timothy Oeltmann, Robert Carson, John R Shannon, Terry Ketch, David Robertson
• Journal: Autonomic neuroscience : basic & clinical (Auton Neurosci) Vol. 116 Issue 1-2 Pg. 1-10 (Nov 30 2004) ISSN: 1566-0702 [Print] Netherlands
• PMID: 15556832 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S., Review)

Chemical References

• Biomarkers
• Catecholamines
• Metanephrine
• Catechol O-Methyltransferase

Topics

• Animals
• Autonomic Nervous System Diseases (blood, diagnosis, urine)
• Biomarkers (blood, urine)
• Catechol O-Methyltransferase (physiology)
• Catecholamines (metabolism)
• Humans
• Metanephrine (blood, urine)
• Models, Chemical
• Models, Neurological