Abstract

Procedure for the quantification of 3-methoxy-4-hydroxyphenethyleneglycol (MHPG) and vanilmandelic acid (VMA) in human serum are described. MHPG was selectively acetylated then determined as its 4-acetyl-di-trifluoroacetyl derivative and VMA as its di-pentabluoropropionyl-methyl ester. Deuterium-labeled MHPG and VMA were used as internal standards. Each of these metabolities and the resprective internal standards was recorded by double ion monitoring respectively, and the ratios were determined for specificity. Assay sensitivities of 1.0 ng/ml for MHPG and 2.0 ng/ml for VMA were achieved using 0.5 ml of serum. Total and free MHPG concentrations in human serum were determined to be 16.5 ng/ml +/- 4.4 (S.D.) and 4.6 ng/ml +/- 1.0 respectively from 10 normal male subjects. Free VMA concentrations were 7.0 ng/ml +/- 1.5; thus the ratio of MHPG/VMA was calculated to be 2.4 +/- 0.7 in these subjects. Of these two major normal metabolites of norepinephrine, MHPG is regarded to be largely derived from the central nervous system while VMA is from the periphery. The procedures are highly specific as well as simple and sensitive enough to permit simultaneous measurement of these two metabolites in a series of multiple samples from an individual.