Estimation of Alternative Metabolic Pathways of Catecholamines in Man
The recent elucidation of the metabolic products of the catecholamines [1,2,3,4] has resulted in an understanding of the pathways of metabolism of these neurohumors. Figure 1 illustrates our current concept of these pathways. Norepinephrine may be N-methylated in some tissues to form epinephrine. Both norepinephrine and epinephrine may be deaminated to form 3,4-dihydroxymandelic aldehyde. This intermediate may undergo oxidation to 3,4-dihydroxymandelic acid (DHMA) or reduction to 3,4-dihydroxyphenylglycol (DHPG). Either of these catechols may then be O-methylated to form 3-methoxy-4-hydroxymandelic acid (VMA) or 3-methoxy-4-hydroxypheny lgly col (MHPG). Norepinephrine and epinephrine may both be O-methylated to form normetanephrine or metanephrine, respectively. Both of these 0-methylated amines form a common intermediate aldehyde which may undergo subsequent oxidation or reduction to form VMA or MHPG by an alternative route.
KeywordsMetabolic Product Adrenal Medulla Simultaneous Injection Autonomic Disorder Catecholamine Metabolism
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