Methodological issues in the measurement of urinary MHPG

The urinary MHPG/creatinine ratio and its relationship to platelet monoamine oxidase activity in abstinent alcoholics

This study was designed to assess the baseline noradrenergic turnover of subgroups of postwithdrawal abstinent alcoholics and healthy controls. The method chosen was an overnight fasting urine sample of the breakdown product of norepinephrine, MHPG, related to urinary creatinine. A comparison was made with platelet monoamine oxidase activity and also within subgroups of the study population. This study found no difference between alcoholics and controls, nor between subgroups of postwithdrawal alcoholics in their level of urinary MHPG corrected for creatinine, and no significant correlation with major subject characteristics or with platelet monoamine oxidase. There was a trend, however, towards a significant correlation with duration of abstinence from alcohol, and there was a correlation with a history of fighting when drinking alcohol, but not with sociopathic traits overall. Within the type 2 alcoholics there was a significant correlation with a history of fighting when drinking and a negative correlation with behavioral tolerance to alcohol. It is possible that only the subset of type 2 alcoholics with certain antisocial characteristics have noradrenergic abnormalities. Although no statistical difference was found between the different groups under study, the information is helpful in increasing understanding of the noradrenergic system in abstinent alcoholics.

Separate determination of human urinary conjugated and unconjugated 3-methoxy-4-hydroxyphenylethyleneglycol

A new determination procedure for human urinary 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) was established. In addition to the previously established solid-phase extraction method for unconjugated MHPG, another solid-phase extraction method for conjugated MHPG was developed. Unconjugated MHPG was adsorbed on a Sep-Pak Diol cartridge and selectively recovered by elution with ethyl acetate. The eluate was evaporated and the residue was redissolved and analyzed by reversed-phase high-performance liquid chromatography with fluorimetric detection. Conjugated (sulfate plus glucuronide) MHPG was adsorbed on a Sep-Pak Accell QMA cartridge and quantitatively eluted with 0.2 M NaCl. After enzymatic hydrolysis, deconjugated MHPG was extracted using a Sep-Pak Diol cartridge and analyzed in the same manner as unconjugated MHPG. The new method is simple and rapid and can quantitate conjugated and unconjugated MHPG discriminatively.

Biogenic amines and their metabolites in body fluids of normal, psychiatric and neurological subjects

The biogenic monoamines and their metabolites have been isolated, identified and quantified in human body fluids over the past forty years using a wide variety of chromatographic separation and detection techniques. This review summarizes the results of those studies on normal, psychiatric and neurological subjects. Tables of normal values and the methods used to obtain them should prove to be useful as a reference source for benchmark amine and metabolite concentrations and for successful analytical procedures for their chromatographic separation, detection and quantification. Summaries of the often contradictory results of the application of these methods to psychiatric and neurological problems are presented and may assist in the assessment of the validity of the results of experiments in this field. Finally, the individual, environmental and the methodological factors affecting the concentrations of the amines and their metabolites are discussed.

Effects of long-term storage on the concentrations of the unconjugated acidic metabolites of the trace amines, indoleamines and catecholamines

The concentrations of urinary phenylacetic, m- and p-hydroxyphenylacetic, mandelic (MA), p-hydroxymandelic, indoleacetic, homovanillic, vanillylmandelic, 5-hydroxyindoleacetic and 3,4-dihydroxyphenylacetic (DOPAC) acids and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) and the concentrations of the above plasma acids (except MA, MHPG and DOPAC) were determined by gas chromatography-mass spectrometry with selected-ion monitoring at the time of receipt of the samples and after three, six and nine months storage at -18 degrees C. The samples were not treated in any way before storage. The concentrations of most of the urinary metabolites declined significantly (analysis of variance) over the nine-month storage period, whereas most of the plasma metabolites did not.

The TRH test and urinary MHPG in unipolar depression

Twenty-five men and 26 women with major unipolar depression were evaluated by the TRH test and urinary MHPG excretion. A significant positive correlation between TSH response to TRH and urinary MHPG was found in the men, though not in the women. These findings suggest that at least for depressed men, central norepinephrine deficiency may be the neurobiological substrate of blunted TSH responses to TRH.

Methodological issues in the measurement of serum TSH--implications for psychiatry

The TSH response to TRH has been reported to be blunted in endogenous depression. We compared two radioimmunoassay (RIA) techniques of TSH in 21 subjects (7 psychiatric inpatients, 14 normal controls) to determine whether differences in assay could account for discrepancies in the reported prevalence rates of blunted TSH responses in depression. A highly significant correlation (p less than 0.001) was found between the delta MAX TASH values of the two assays. The mean delta MAX TSH of one assay was significantly greater than the mean of the second assay. One assay yielded 6 blunted TSH responses to TRH, while the other yielded 9 such responses. Different TSH assay methods might account for discrepancies of the prevalence rates of blunted TSH response in depression.

Monoamine metabolites as predictors of antidepressant response: a critique

Monoamine metabolite measurements are being increasingly used for making nosological, symptomatological and pharmacological profiles of the affective disorders. A number of unresolved methodological issues question the validity of using baseline metabolite levels for predicting treatment response. Some studies show correlations between baseline metabolite levels and response to treatment with specific antidepressant agents. Effects of antidepressant treatment on metabolite levels may be useful in predicting drug response.

Depressive symptom patterns and urinary MHPG excretion

Twenty-four hour urinary excretion of 3-methoxy-4-hydroxyphenyl-glycol (MHPG) was analyzed in 48 unipolar and 19 bipolar depressed patients and 16 healthy controls. All patients were interviewed using the Schedule for Affective Disorders and Schizophrenia. Various symptoms and descriptive variables were correlated univariately with urinary MHPG in two random groups, and those items showing a trend in both splits were further reduced by a multiple regression technique, first on each split separately and finally on the pooled sample. Urinary MHPG correlated significantly both in uni- and multivariate tests with age (positively, but only in females), altered motor activity (summed scores of agitation and retardation during the worst week of present or recent depression), and with existence of at least one suicide attempt before the present depressive episode (last items negatively). There were no differences between unipolar and bipolar patients, or between any patient group and the healthy controls. Males excreted about 25% more MHPG than females. Levels of MHPG in urine and cerebrospinal fluid were highly significantly intercorrelated.