[Determination of four biogenic amine metabolites in urine by high-performance liquid chromatography]

OBJECTIVE

To establish a method for simultaneously determining vanilmandelic acid (VMA), 5-hydroxyindoleacetic (5-HIAA), 3, 4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in urine by high-performance liquid chromatography (HPLC).

METHODS

After being filtered with a 0.45 µm membrane syringe filter, the urinary samples were injected directly into the HPLC system using a C18 chromatographic column and a fluorescence detector. The excitation and emission wavelengths were chose as 280 nm and 315 nm, respectively, and the urinary samples were carried with a mobile phase of methanol-0.1 mol/L phosphate buffered solution (V/V = 20:80) at a flow rate of 1.0 ml/min and an injection volume of 20 µl.

RESULTS

Using the method reported here, the correlation coefficients of VMA, 5-HIAA, DOPAC, and HVA were 0.9999, 0.9998, 0.9997, 0.9999, respectively, over linear ranges of 0-2.5, 0-2.0, 0-2.0, and 0-2.5 µg/ml, the minimum detectable concentrations were 0.006, 0.008, 0.012, and 0.0082 µg/ml, the average precisions were 4.2%, 3.7%, 4.9%, and 3.6%, and the recovery rates were 91%∼102%, 93%∼101%, 94%∼101%, and 89%∼ 102%.

CONCLUSION

This determination method is simple, efficient, accurate, and sensitive for the simultaneous detection of VMA, 5-HIAA, DOPAC, and HVA in urine.

Quantification of biogenic amines by microchip electrophoresis with chemiluminescence detection

A highly sensitive microchip electrophoresis (MCE) method with chemiluminescence (CL) detection was developed for the determination of biogenic amines including agmatine (Agm), epinephrine (E), dopamine (DA), tyramine, and histamine in human urine samples. To achieve a high assay sensitivity, the targeted analytes were pre-column labeled by a CL tagging reagent, N-(4-aminobutyl)-N-ethylisoluminol (ABEI). ABEI-tagged biogenic amines after MCE separation reacted with hydrogen peroxide in the presence of horseradish peroxidase (HRP), producing CL emission. Since no CL reagent was added to the running buffer, the background of the CL detection was extremely low, resulting in a significant improvement in detection sensitivity. Detection limits (S/N=3) were in the range from 5.9x10(-8) to 7.7x10(-8) M for the biogenic amines tested, which were at least 10 times lower than those of the MCE-CL methods previously reported. Separation of a urine sample on a 7 cm glass/poly(dimethylsiloxane) (PDMS) microchip channel was completed within 3 min. Analysis of human urine samples found that the levels of Agm, E and DA were in the ranges of 2.61x10(-7) to 4.30x10(-7) M, 0.81x10(-7) to 1.12x10(-7) M, and 8.76x10(-7) to 11.21x10(-7) M (n=4), respectively.

Liquid chromatography method for detecting native fluorescent bioamines in urine using post-column derivatization and intramolecular FRET detection

Liquid chromatography (LC) with fluorescence detection is described for simultaneous determination of native fluorescent bioamines (indoleamines and catecholamines). This is based on intramolecular fluorescence resonance energy transfer (FRET) in an LC system following post-column derivatization of native fluorescent bioamines' amino groups with o-phthalaldehyde (OPA). OPA fluorescence was achieved through an intramolecular FRET process when the molecules were excited at maximum excitation wavelength of the native fluorescent bioamines. Bioamines separated by reversed-phase LC on ODS column were derivatized with OPA and 2-mercaptoethanol. This method provides sufficient selectivity and sensitivity for the determination of normetanephrine, dopamine, tyrosine, 5-hydroxytryptamine, tryptamine, and tryptophan in healthy human urine without prior sample purification.

Amino acid profiling in urine by capillary zone electrophoresis - mass spectrometry

Analysis of amino acid profiles in urine and plasma is an essential part of modern clinical diagnostic routine. Here we present an approach for the analysis of amino acids in urine by capillary electrophoresis/time-of-flight (TOF) mass spectrometry. At first a method combining improved separation, high dynamic range, and high sensitivity is presented. Detection limits in the mid nM-range are achieved through the use of pH-mediated stacking injection in combination with modern TOF detection technology. The method can be easily applied to detect differences in the amino acid profile in urine in a clinical context. Moreover, beside amino acids low molecular weight amines, peptides and related metabolites can be profiled. As a proof of concept, urine samples from patients suffering from osteoarthritis have been analyzed. Finally, the introduction of multivariate data analysis in the work flow was evaluated on spiked urine samples and real clinical material.

Determination of Catecholamines and Indoleamines in Human Urine Based on Intramolecular Excimer-forming Derivatization and Fluorescence Detection

A liquid chromatographic (LC) determination of catecholamines and indoleamines is described. This is based on intramolecular excimer-forming fluorescence derivatization with 4-(1-pyrene)butanoyl chloride, followed by reversed-phase LC. The analytes, containing an amino moiety and phenolic hydroxyl moieties in a molecule, were converted to the corresponding polypyrene-labeled derivatives by one-step derivatization. They afforded intramolecular excimer fluorescence, which can clearly be discriminated from the normal fluorescence emitted from reagent blanks. The detection limits (S/N = 3) for catecholamines and indoleamines were femto-mole levels per 20-microL injection. Furthermore, this method was applied to a urine assay.

Sample injection in capillary electrochromatography by heart-cut technique

The splitter working in heart-cut regime was used for sample injection in capillary electrochromatography. The principle was implemented in an automated microgradient system allowing to inject from microlitre down to nanolitre volumes with high repeatability and minimal extra-column band broadening. The apparatus is able to deliver discrete volumes of liquids at a preset volumetric flow rate and to stop and restore the flow at any moment. This brings a high degree of liquid manipulation flexibility. An extremely low split ratio is sufficient during the analysis, which saves mobile phase consumption substantially. The key parameters influencing the function of the heart-cut splitter were characterised. The function of the apparatus was demonstrated under isocratic, preconcentration and gradient capillary electrochromatography separation conditions. In all cases the statistic evaluation of the main parameters was performed, showing that high repeatability of retention times, peak heights and areas was achieved.

Evaluation of the nocturnal levels of urinary biogenic amines in men exposed overnight to 50-Hz magnetic field

The aim of this study was to determine whether exposure to magnetic fields might affect human health and to look for possible effects of acute exposure (9 hours) to 50-Hz magnetic fields (10 microT) on the urinary concentration of biogenic amines. Thirty-two young men (20-30 years old) were divided into two groups (sham-exposed and exposed group) of 12 to 16 subjects each. All subjects participated in two 24-hour experiments to evaluate the effects of both continuous and intermittent exposure to magnetic fields. The subjects were exposed to the magnetic field from 2300 to 0800, while lying down. Total urine (from 2300 to 0800) was collected at 0800. The results (expressed as a ratio of biogenic amine excretion to creatinine excretion (nmol/mmol)) did not differ significantly between sham-exposed and exposed men for any of the parameters measured: adrenaline, noradrenaline, dopamine, dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid. These results suggest that nocturnal exposure to either continuous or intermittent 50-Hz magnetic fields of 10 microT does not affect, at least under our experimental conditions, the nocturnal excretion of biogenic amines in healthy young men.

Amplification of small analytes in polymer solution by capillary electrophoresis

We report concentration methods for the analysis of small solutes by capillary electrophoresis in conjunction with laser-induced native fluorescence using a Nd:YAG laser. After injecting samples, poly(ethylene oxide) (PEO) in the anode reservoir entered a capillary filled with Tris-borate buffer. When migrating in PEO solution, the analytes slowed down and stacked at the interface between the sample zone and PEO solution. As a result, the limits of detection (LODs) down to 8 pM for 2-naphthalenesulfonic acid and 70 pM for L-tryptophan have been achieved when injecting at 30 cm height for 120 s and 230 s, respectively. Such low LODs are partially due to the effects of NaCl in the samples and PEO on the fluorescence characteristics of the analytes. In addition, the concentrations of NaCl and PEO have great impacts on the migration of the analytes and electroosmotic flow, thereby affecting resolution and speed. Without pretreatment, the determinations of five important markers in urine samples and two acids in a cerebrospinal fluid sample have been performed separately, with the relative standard deviations of the concentrations less than 3.6%. Furthermore, by applying a short plug of low-pH buffer after injection, the analysis of greater volumes of the urine sample has been carried out, resulting in detecting more peaks.

Measurement of nitrite and nitrate in plasma, serum and urine of humans by high-performance liquid chromatography, the Griess assay, chemiluminescence and gas chromatography-mass spectrometry: interferences by biogenic amines and N(G)-nitro-L-arginine analogs

In this paper, the HPLC method for the measurement of nitrite and nitrate in serum of humans newly reported by E1 Menyawi et al. is discussed, especially in regard to the extremely low nitrate levels measured in serum of healthy humans. From the discussion, it is concluded that: (1) Biogenic amines at physiological concentrations do not significantly interfere with the batch Griess assay. (2) The HPLC method of E1 Menyawi et al. does not reveal accurate levels for serum nitrate. (3) In serum and plasma of healthy humans, nitrate ranges within 15-70 microM. (4) Exogenous NG-nitro-L-arginine analogs can interfere with the measurement of nitrate in human plasma and urine by the batch Griess assay, chemiluminescence and GC-MS; interferences can be effectively eliminated by solid-phase extraction on cation-exchangers.

Monoamine oxidase A deficiency: biogenic amine metabolites in random urine samples

We have recently described an association between abnormal behaviour and monoamine oxidase A (MAO-A) deficiency in several males from a single large Dutch kindred. A characteristically abnormal excretion pattern of biogenic amine metabolites was present in 24-hour urine of affected males. Because of this strikingly abnormal metabolite pattern observed in 24 hour urine samples of MAO-A deficient males we hypothesized that it should be possible to diagnose this condition by examining random urine samples. We therefore studied multiple urine samples obtained over a two-week study period from two males with selective MAO-A deficiency. The results demonstrate that the characteristic abnormalities in the excretion of biogenic amines and their metabolites were faithfully present in every one of 12 independent samples obtained from the MAO-A deficient males over the two-week study period. We conclude that MAO-A deficiency can be reliably diagnosed by measuring the ratio of normetanephrine (NMN) to VMA (or that of NMN to MHPG) in random urine samples.

Differential trace amine alterations in individuals receiving acetylenic inhibitors of MAO-A (clorgyline) or MAO-B (selegiline and pargyline)

Marked, dose-dependent elevations in the urinary excretion of phenylethylamine, para-tyramine, and meta-tyramine were observed in depressed patients treated for three or more weeks with 10, 30, or 60 mg/day of the partially-selective inhibitor of MAO-B, selegiline (l-deprenyl). In comparative studies with other, structurally similar acetylenic inhibitors of MAO, pargyline, an MAO-B > MAO-A inhibitor used in doses of 90 mg/day for three or more weeks, produced elevations in these trace amines which were similar to those found with the highest dose of selegiline studied. Clorgyline, a selective inhibitor of MAO-A used in doses of 30 mg/day for three or more weeks (a dose/time regimen previously reported to reduce urinary, plasma, and cerebrospinal fluid 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) > 80%, indicating a marked inhibitory effect on MAO-A in humans in vivo) produced negligible changes in trace amine excretion. In comparison to recent studies of individuals lacking the genes for MAO-A, MAO-B, or both MAO-A and MAO-B, the lack of change in trace amine excretion in individuals with a mutation affecting only MAO-A is in agreement with the observed lack of effect of clorgyline in the present study. Selegiline produced larger changes in trace amines--at least at the higher doses studied--than found in individuals lacking the gene for MAO-B, in agreement with other data suggesting a lesser selectivity for MAO-B inhibition when selegiline was given in doses higher than 10 mg/day. Overall, trace amine elevations in individuals receiving the highest dose of deprenyl or receiving pargyline were approximately three to five-fold lower than the elevations observed in individuals lacking the genes for both MAO-A and MAO-B, suggesting that these drug doses yield incomplete inhibition of MAO-A and MAO-B.

Effects of Celastrus paniculatus on passive avoidance performance and biogenic amine turnover in albino rats

The effects of an indigenous drug, Celastrus oil, extracted from the seeds of Celastrus paniculatus on learning and memory in a two compartment passive avoidance task was studied in albino rats. The effects on the contents of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) in the brain and on the levels of their metabolites both in the brain and urine were also assessed. Significant improvement was observed in the retention ability of the drug treated rats compared with the saline administered controls. The contents of NE, DA and 5-HT and their metabolites in the brain were significantly decreased in the drug treated group. The urinary metabolite levels were also significantly decreased except for total 3-methoxy-4-hydroxyphenyl glycol. These data indicate that Celastrus oil causes an overall decrease in the turnover of all the three central monoamines and implicate the involvement of these aminergic systems in the learning and memory process.

Obsessive-compulsive symptom clusters and urinary amine correlates in Tourette syndrome

This study was conducted to identify clusters of obsessive-compulsive characteristics in Tourette syndrome subjects and to explore their neurochemical correlates. Patients completed a 40-item questionnaire assessing obsessive-compulsive symptoms. Each subject had a 24-hour urine specimen collected and analyzed for a variety of biogenic amines and their metabolites. Factor analysis identified eight symptom clusters, the majority of which appeared to reflect obsessive symptoms. Consistent relationships were observed between symptom clusters and levels of catecholamine and indolamine amines and metabolites. Overall, the primary metabolite of serotonin, 5-hydroxyindoleacetic acid, appeared to be the most highly correlated with the individual obsessive-compulsive symptoms.

Urinary excretion of bioactive amines and their metabolites in psychiatric patients receiving phenelzine

Phenelzine [2-phenylethylhydrazine] (PLZ), a potent inhibitor of monoamine oxidase (MAO)-A and -B, is used widely in psychiatry. We have studied the effects of PLZ administration on urinary excretion of several bioactive amines and their metabolites in psychiatric patients. Urine samples (24-hour) were collected prior to treatment and again at 2 and 4 weeks of treatment with PLZ (30-90 mg daily in divided doses). Amines and metabolites analyzed included 2-phenylethylamine (PEA), m- and p-tyramine (m- and p-TA), phenylacetic acid (PAA), m- and p-hydroxyphenylacetic acid (m- and p-OH-PAA), tryptamine (T), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), normetanephrine (NME), 3-methoxy-4-hydroxyphenylglycol (MHPG), 3-methoxytyramine (3-MT), and homovanillic acid (HVA). Levels of PEA, p-TA, 5-HT, and T were elevated during treatment with PLZ, but no significant changes in urinary excretion of the acid metabolites PAA, p-OH-PAA, and 5-HIAA were observed. Urinary levels of the noradrenaline metabolites NME and MHPG were increased and decreased, respectively; a similar pattern was observed with the dopamine metabolites 3-MT and HVA. There was an elevation in levels of m-TA and a decrease in its acid metabolite m-OH-PAA during the treatment with PLZ.

The effect of the MAO-A selective inhibitor brofaromine on the plasma and urine concentrations of some biogenic amines and their acidic metabolites in bulimia nervosa

1. Brofaromine or placebo were administered to female bulimia nervosa patients over a period of eight weeks. Plasma and urinary trace amines, their acidic metabolites and the acidic metabolites of the catecholamines and serotonin were assessed prior to treatment and at four and eight weeks after commencement of treatment. 2. The levels of both plasma and urinary homovanillic and vanilmandelic acids declined significantly during the first four weeks of treatment with brofaromine and then partially recovered to pre-drug levels by the eighth week. 5-Hydroxyindoleacetic acid levels were not affected by drug treatment at the times assessments were made. Urinary tryptamine increased significantly during the first four weeks of brofaromine treatment then partially recovered towards pre-drug levels by the eighth week. No effect from placebo treatment was observed.

[The content of free amino acids and biogenic amines in the urine of hypertension patients]

Contents of free amino acids and some biogenic amines were studied in hypertonic patients at the age of 40-50 years. The study demonstrates quantitative changes in levels of free amino acids and some biogenic amines caused by disorders of protein metabolism. The data obtained may be used for diagnosis of hypertonic diseases.

Influence of a serotonin- and dopamine-rich diet on platelet serotonin content and urinary excretion of biogenic amines and their metabolites

Using high-performance liquid chromatography and gas chromatography, we reevaluated the 24-h influence of a serotonin- and dopamine-rich diet on platelet serotonin and serotonin, 5-hydroxyindoleacetic acid (5-HIAA), and major catecholamine metabolites in the urine of 15 healthy adults. Although there were significant responses in urinary free serotonin and catecholamine metabolites, their concentrations did not exceed the upper limits of the reference ranges for any of the participants. For urinary 5-HIAA, pronounced effects were observed within 2-4 h. After 6-8 h, results for 11 participants exceeded the upper limit of the reference range. The median recovery of dietary serotonin as urinary 5-HIAA was 20% and subject to a large range (1-50%). There was no significant change in platelet serotonin. We conclude that, using specific analytical methods, no dietary restrictions need be imposed to diagnose catecholamine (metabolite)-producing tumors. For diagnosis of carcinoids on the basis of urinary 5-HIAA it is appropriate to completely abstain from serotonin-containing foods for greater than or equal to 12 h before testing. Platelet serotonin is a more sensitive marker for carcinoids that produce only small amounts of serotonin, and is unaffected by dietary serotonin.

Urinary amines in adults with Tourette's syndrome

Urinary amines and their metabolites were examined in 32 adults who met DSM-III-R diagnostic criteria for Tourette's Syndrome. These patients were compared with a control group that was of similar age and sexual representation. Analyses revealed significantly lower levels of 3-methoxy-4-hydroxyphenylglycol and serotonin as well as the metabolites of several "trace" amines including indoleacetic acid and m- and p-hydroxyphenylacetic acid. These findings persisted when Tourette's Syndrome patients taking medications were eliminated from the analyses. These data are consistent with reports of neurotransmitter abnormalities in children with Tourette's Syndrome. The differences in several trace amine metabolites suggest that the pathophysiology in this disorder is complex and involves a number of neurotransmitter and neuromodulator systems.

Biogenic amines in anorexia nervosa: circadian rhythm in urinary excretion and influence of posture and physical task load on plasma catecholamines

To investigate the sympathetic response in anorexia nervosa (AN) patients to stimuli occurring in normal life, biogenic amines were studied in 10 female outpatients. As control groups 10 lean and 10 normal weight healthy female subjects were included. It was hypothesized that the lean control group would have intermediate values between the AN patients and the normal weight controls. The AN patients and the lean controls had a mean underweight of 33.1% and 13.7%, respectively. For the excretion in 24-hr urine, differences among the groups were observed for several compounds, unexpectedly the values being lowest for the patients and highest for the lean controls. Furthermore, the lean controls had a higher excretion of a number of compounds in diurnal than in nocturnal urine, whereas this effect was absent or reversed for the AN patients and intermediate for the normal weight controls. Plasma norepinephrine was highest in the patients and lowest in the lean controls. The catecholamine response to postural changes and physical exercise did not differ among the groups. The results obtained indicate neither a (linear) relationship between underweight and the metabolism of biogenic amines nor a disturbed response to sympathetic stimulation in AN, but suggest an altered metabolism of biogenic amines in patients suffering from AN.

Quality assurance for biogenic amines with authentic patient specimens

The measurement of biogenic amines and metabolites is essential for diagnosis and follow-up of neural crest tumors. A Quality Assurance programme involving the distribution of urine specimens obtained from patients with neural crest and related tumors was conducted by the Australian Association of Clinical Biochemists' Working Party on Biogenic Amines in 1988. Fifty laboratories participated in the programme and measured a number of analytes with a variety of methods. These included high performance liquid chromatography with electrochemical detection (HPLC-EC), spectrophotometry, fluorescence, fluorescence polarization immunoassay (Abbott TDX) and gas chromatography--mass spectroscopy (GC-MS). The results of this survey indicated that fluorimetric methods for catecholamines are unreliable as they are subject to interference particularly by Labetalol. Twice as many laboratories utilized catecholamines rather than metanephrines for detection of pheochromocytoma. 5-HIAA appears to be the analyte measured with the least accuracy, particularly with spectrophotometric methods of analysis. Several laboratories would have failed to diagnose some neural crest tumors and need to improve their performance.

Urinary amines in Tourette's syndrome patients with and without phenylethylamine abnormality

Previous data indicated a subgroup of Tourette's syndrome patients with a beta-phenylethylamine (PEA) level that was lower than all subjects in a control group matched for age and education. The current study compared the subgroups of Tourette's syndrome patients (n = 28) from the previous study with 20 control subjects in regard to other amines and metabolites. Patients with low levels of PEA were also found to have lower levels of 3-methoxy-4-hydroxy-phenylglycol, normetanephrine, serotonin, m-tyramine, and p-tyramine. There was also some evidence of dopaminergic abnormalities in the low-PEA subgroup. These data provide suggest a role of PEA in the pathophysiology of some patients with Tourette's syndrome. This effect may be mediated through other neurotransmitter systems.

Marked amine and amine metabolite changes in Norrie disease patients with an X-chromosomal deletion affecting monoamine oxidase

Urinary and plasma amines and amine metabolites were quantified in two individuals with Norrie disease resulting from a deletion in chromosomal region Xp11.3, recently reported to be associated with absence of the gene encoding monoamine oxidase (MAO)-A and nondetectable MAO-A activity in fibroblasts and MAO-B activity in platelets. Marked (four-to 100-fold) elevations in levels of urinary phenylethylamine, o-tyramine, and m-tyramine (which are preferential substrates for MAO-B) and marked reductions (90%) in levels of 3-methoxy-4-hydroxyphenylglycol (a deaminated metabolite of norepinephrine, a preferential substrate for MAO-A) in urine and plasma confirmed the presence of a systemic, functionally significant reduction in the activities of both MAO isozymes. The magnitude of these changes, which are equivalent to those found in subjects taking MAO-inhibiting antidepressants, suggests that early initiation of dietary and drug restrictions may be clinically important in these and other patients with X-chromosomal mutations involving MAO. These findings further support the proposition that the MAOA and MAOB genes are located in close proximity on the X chromosome. Negligible changes in the metabolites of dopamine and serotonin raise the possibility that other metabolic pathways are of importance for their production, that dietary or intestinal bacterial sources contribute substantially to the presence of these amine metabolites in urine, or both.

Analysis of biogenic amines and their metabolites in biological tissues and fluids by gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS)

GC-NICIMS has been employed in the analysis of biogenic amines and their metabolites in human urine and human, bovine and porcine aqueous and vitreous humour. Several new chemical derivatization procedures have been developed in order to analyse these compounds. Concentrations of octopamines and synephrines were determined in urine from treated and untreated hypertensive subjects and normotensive individuals; there were no significant differences in concentrations of these metabolites between these groups. Human urine contained several dihydroxy-phenylethylamines which have not been reported as natural metabolites before and also 5- and 6-hydroxydopamine in relatively large amounts. Aqueous and vitreous humour contained very low quantities of noradrenaline, tyramine and dopamine but measurements were inconsistent because sometimes the levels were below the limits of detection. Metabolites of a number of biogenic amines were readily detected in aqueous and vitreous humour.

Effects of chlorpromazine on hypothalamic aminergic neurons and stress responses in moderate cold

Guinea-pigs were treated with chlorpromazine or 0.9% NaCl and exposed to +4 degrees C or +23 degrees C for 2 h. Hypothalamic noradrenaline (NA), dopamine (DA), 5-hydroxytryptamine (5-HT), 3-methoxy-4-hydroxyphenylethylene-glycol (MHPG), homovanillinic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were determined by high-performance liquid chromatography. Serum and urinary catecholamines, muscle and liver glycogen and blood glucose were also measured. Chlorpromazine caused deep hypothermia at this moderately cold temperature and slight hypothermia at room temperature. Cold increased the activity of noradrenergic and serotonergic neurons, as indicated by the increase in hypothalamic MHPG and 5-HIAA and also the MHPG:NA and 5-HIAA:5-HT ratios. A tendency towards drug-induced inhibition of hypothalamic serotonergic neurons was seen, although this was not significant. A drug-induced inhibition of noradrenergic neurons could not be ruled out. Increased drug-induced turnover of DA was observed in the cold, and a tendency in the same direction was seen at room temperature. Excretion of DA into the urine was induced by chlorpromazine. The hypothermic guinea-pigs had low serum catecholamines, indicating diminished sympathetic activity, but high urinary catechols, a sign of cold stress.

Chromatographic approaches to signal and selectivity enhancement for determination of biogenic amines by liquid chromatography with amperometric detection

A variety of chromatographic approaches are detailed for enhancement of signal and selectivity for determination of biogenic amines by HPLC with amperometric detection. Microbore HPLC columns offer significant signal enhancement due to the reduced elution volume. Selection of novel surfactants such as N-methyl oleoyl taurate allows conversion of reverse phase materials to strong cation exchangers, adding selectivity. Large injection volumes can be applied to these columns due to their strong cationic nature using a noneluting matrix. Additional sensitivity can be obtained by using a mobile phase of relatively high pH to take advantage of intramolecular cyclization.

A comparison of the gas chromatographic and mass spectrometric properties of the pentafluoropropionyl and heptafluorobutyryl derivatives of the methyl, trifluoroethyl, pentafluoropropyl and hexafluoroisopropyl esters of twelve acidic metabolites of biogenic amines

The gas chromatographic and mass spectrometric properties of the methyl, trifluoroethyl, pentafluoropropyl and hexafluoroisopropyl esters of the pentafluoropropionyl and heptafluorobutyryl derivatives of twelve important acidic metabolites of biogenic amines have been investigated. The optimum derivatization conditions for the different classes of metabolites have been established and the byproducts formed in some of the derivatizations have been identified. Under certain derivatizing conditions, back-exchange of deuterium in the labelled internal standards was observed. No single derivative appears to be ideally suitable for the simultaneous quantitative analysis by GC/MS of all twelve metabolites, so extracts of plasma and urine were split and a combination of the methyl or trifluoroethyl esters of the pentafluoropropionyl derivatives were used.

N-propargylbenzylamine, a major metabolite of pargyline, is a potent inhibitor of monoamine oxidase type B in rats in vivo: a comparison with deprenyl

In an effort to explore the contribution of the metabolites of pargyline towards the in vivo inhibition of monoamine oxidase (MAO), the effects of pargyline and its major metabolites on the production and metabolism of a number of biogenic amines were studied in rats. The administration of pargyline gave rise to three major ethyl acetate extractable metabolites: benzylamine, N-methylbenzylamine and N-propargylbenzylamine (NPB). Only NPB demonstrated in vivo monoamine oxidase inhibitory properties at an acute dose of 30 mg kg-1. The acute effects of pargyline, NPB, and deprenyl on urine and brain concentrations of a number of biogenic amines (phenylethylamine (PEA), m- and p-tyramine, noradrenaline (NA), dopamine, and 5-hydroxytryptamine (5-HT) and their metabolites were evaluated. Increased urine and brain concentrations of PEA were considered to represent in vivo inhibition of type B MAO while decreased concentrations of NA and 5-HT metabolites were regarded as indicators of an in vivo inhibition of MAO type A. NPB, like deprenyl and pargyline, significantly increased urine and brain PEA while only pargyline reduced 5-HT metabolism, suggesting that the metabolism of pargyline to NPB may contribute towards the MAO type B inhibitory effects of pargyline in vivo. Since the therapeutic benefits of MAO inhibitors in clinical practice usually require some period of chronic treatment, the chronic effects of repeated 14 daily doses of the above MAO inhibitors on central and peripheral biogenic amines were evaluated at the following times: during treatment, one day and five days after termination of treatment. The biochemical changes observed during the course of chronic NPB, pargyline and deprenyl treatments generally follow the expected in vitro characteristics of these drugs, but the detailed changes observed suggest clear differences. For example, the in vivo effect of pargyline on urine 5-hydroxyindoleacetic acid excretion was considerably weaker than its effect on the excretion of NA and dopamine metabolites. These changes are opposite to the in vitro effects of pargyline on 5-HT, dopamine and NA oxidative deamination. Inhibitions of the metabolism of all the amines studied were clearly observed during chronic MAOI treatments, but these effects were less evident five days after the end of treatment, suggesting an almost normal metabolism of biogenic amines. It is concluded that while MAO inhibitors may be the primary compound responsible for MAO inhibition, the effects of their metabolites in some cases may also play equally important roles in the regulation of monoamines both in the periphery and the brain. Thus, as demonstrated here, NPB was found to be as potent as pargyline and deprenyl with regard to its in vivo MAO type B inhibitory properties.

High-performance liquid chromatography of biogenic amines and metabolites in brain, cerebrospinal fluid, urine and plasma

A method for high-performance liquid chromatographic separation and electrochemical detection of biogenic amines and metabolites in a variety of biological matrices is described. The method employs either homogenization, precipitation or dilution followed by direct injection of the samples and permits the chromatographic resolution of dopamine, norepinephrine, epinephrine, serotonin (5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in brain; 3-methoxy-4-hydroxyphenylglycol, DOPAC, 5-HIAA and HVA in cerebrospinal fluid; 5-HIAA, HVA and 5-HT in plasma; and 5-HIAA and HVA in urine. Alterations in chromatographic conditions, voltammetry and in vivo pharmacological manipulations are employed to verify the identity of the putative neurotransmitter and metabolite peaks in the biological samples.

Simultaneous analysis of twelve biogenic amine metabolites in plasma, cerebrospinal fluid and urine by capillary column gas chromatography-high-resolution mass spectrometry with selected-ion monitoring

A procedure is described for the simultaneous determination of twelve acidic and alcoholic metabolites of trace and catecholic biogenic amines in plasma, cerebrospinal fluid and urine by capillary column gas chromatography--high-resolution mass spectrometry. Protein precipitation with sulphosalicylic acid, derivatization with two different reagent systems, final sample clean-up with a buffer wash and a program for automatically changing the reference mass of the mass spectrometer to suit each group of compounds as they are eluted from the column, are the main novel features of the procedure. A brief description of the synthesis of the deuterium-labelled internal standards is provided. The procedure is applied to biological samples and a comparison to reported values is given.

Effects of intraventricular injections of 6-hydroxydopamine on amine metabolites in rat brain and urine

The effects in rats of intraventricular injections of 6-hydroxydopamine (6-OHDA) on the urinary excretion 1-3 weeks later of 3-methoxy-4-hydroxyphenethylene glycol (MHPG), 3,4-dihydroxyphenethanol (DHPE), 3-methoxy-4-hydroxyphenethanol (MHPE), p-hydroxyphenylglycol (pHPG), homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were examined. The excretion of MHPG was decreased to 63 and 71% of control on days 7 and 14, respectively, but had returned to control levels by day 23, even though the brain levels were decreased by 87%. Free and total HVA excretion was reduced on both days 7 and 23, but free and total DOPAC was reduced only on day 7. Based on these data, it can be estimated that about 39% of the free and 46% of the total HVA in urine originates in the CNS. The excretion of conjugated HVA was decreased by 70-80%, but this decrease does not support the notion that the conjugated form of HVA is derived principally from the brain and thus serves as a better marker of brain dopamine metabolism, since the level of this metabolite in the brain was not correspondingly decreased but was instead increased. Urinary DOPAC levels were generally more variable and derived to a greater extent from the periphery; therefore, DOPAC appears to be less suitable than HVA as a marker of brain dopamine. The results also indicate that as much as 35% of the urinary MHPG may originate in the CNS, although compensatory changes in catecholamine metabolism in either the brain or in the periphery may have somewhat influenced this estimate. The results also suggest that at least as much pHPG as MHPG in urine derives from the CNS. The data are consistent with the idea that the neutral dopamine metabolites largely derive from the brain, but the relatively small depletion in their brain levels produced by 6-OHDA prevented the exact proportion being determined accurately.

Pharmacokinetics of oral moclobemide in healthy human subjects and effects on MAO-activity in platelets and excretion of urine monoamine metabolites

The plasma concentrations of the MAO-inhibitor moclobemide (Ro 11-1163) were determined in six healthy male subjects after oral (tablets) administration. Effects on MAO activity in platelets and excretion of monoamine metabolites in urine were investigated. The design of the study was a double-blind cross-over study with single oral doses of placebo, 50, 100 and 200 mg of moclobemide. The elimination profile of the drug showed that the half life of the unchanged drug ranged between 1 and 2 h except in one subject with a half-life of about 4 h. The mean bioavailability calculated using flow model concepts was F = 0.43 after 50 mg, F = 0.47 after 100 mg and F = 0.59 after 200 mg. The outlier with a t 1/2 of 4 h was found to have a bioavailability of more than 0.80 after all 3 doses. The slightly increasing bioavailability with higher doses was interpreted as evidence of saturable hepatic first-pass elimination of the drug. MAO activity in platelets was measured before and 2, 6 and 24 h after drug administration. No inhibition of platelet MAO was obtained at any point in time or dose level, as to be expected since moclobemide preferentially inhibits MAO A. Urine excretion of the monoamine metabolites homovanillic acid (HVA), dihydroxyphenylacetic acid (DOP-AC), 3-methoxy-4-hydroxy-phenylglycol (MOPEG) and 5-hydroxyindoleacetic acid (5-HIAA) was followed during 48 h after placebo, 50 and 200 mg of moclobemide. Time but not dose contributed significantly to the variability in excretion of the monoamine metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of urinary excretion of biogenic amine metabolites in epilepsy

Urinary total catecholamines, their metabolites, and a metabolite of serotonin have been investigated in 20 patients with epilepsy, and in 10 controls. The levels of total catecholamines, vanillyl mandelic acid and 5-hydroxyindole acetic acid in epileptics were not significantly different from the controls. However, the mean 3-methoxy-4-hydroxyphenylglycol, excretion in cases of epilepsy was significantly increased as compared to the control group. It is concluded that a central catecholaminergic disturbance is involved in the pathogenesis of epilepsy.

CSF and urinary biogenic amines and metabolites in depression and mania. A controlled, univariate analysis

Levels of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in the CSF, and norepinephrine (NE), epinephrine (E), vanillylmandelic acid, normetanephrine, metanephrine, and MHPG in the urine, were measured in 151 hospitalized patients with affective disorders and in 80 healthy controls following a two-week drug-free period. Unipolar and bipolar depressed subjects differed only in NE and E levels. Compared with controls, depressed subjects had higher CSF MHPG levels, women had higher 5-HIAA levels, and men had lower HVA levels. All urinary metabolites were elevated in depression and mania, with the exception of MHPG. The patterns of NE-E differences discriminated among the forms of affective disorders. These data suggest an imbalance of monoamine transmission in depression, characterized by the hyperactive sympathetic nervous system and adrenal medulla. However, MHPG may not be the measure of choice to reflect this imbalance, necessitating measurement of total body monoamine output.

Study of neurotransmitters in premature infants with or without apnea of prematurity

Twelve-hour urinary excretion of 4-hydroxy-3-methoxymandelic acid (VMA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) was studied in 20 premature infants, 8 without apnea and 12 with apnea. All infants were studied at 1-3 days of postnatal age (before apnea). Nonapneic infants were restudied at 10-15 days of postnatal age. Apneic infants were also restudied 24 h after apnea. Apnea was not associated with decreased urinary excretion of VMA and MHPG. Only HVA, when expressed as microgram/kg body weight, was significantly lower after the onset of apnea. This difference disappeared when HVA was expressed as microgram/mg creatinine. We suggest that apnea of prematurity may not be related to the immaturity of catecholamine pathways.

Excretion of biogenic amine metabolites in anorexia nervosa

Urinary metabolites of catecholamines and indoleamines have been investigated in 16 patients with anorexia nervosa (AN) and 13 controls using a HPLC-method. Vanillic mandelic acid, 3-methoxy-4-hydroxyphenylglycol, homovanillic acid, 3,4-dihydroxyphenylacetic acid, 5-hydroxyindole acetic acid and indoleacetic acid were significantly decreased in the pre-treatment phase. In four patients long-term treatment including parenteral and enteral nutrition together with psychological methods resulted in an increase in the levels of these substances and this correlated with increased weight gain and urinary creatinine. It is concluded that both central and peripheral disturbances are involved in AN, particularly with regard to biogenic amine metabolism.

Metabolism of (-) deprenyl to amphetamine and methamphetamine may be responsible for deprenyl's therapeutic benefit: a biochemical assessment

The urinary excretion of some important phenylethylamines, catecholamines, their metabolites, amphetamine, and methamphetamine were measured in parkinsonian patients on Sinemet (L-dopa plus carbidopa, a peripheral dopadecarboxylase inhibitor) and depressed patients after chronic (-) deprenyl treatment. Deprenyl was efficiently metabolized to amphetamine and methamphetamine. It increased the excretion of phenylethylamine and of m- and p-tyramine, and reduced the output of norepinephrine metabolites, but failed to alter the excretion of dopamine-deaminated metabolites. These changes were attributed more to amphetamine and methamphetamine than to inhibition of monoamine oxidase type B. Sinemet treatment alone increased the excretion of dopamine, 3-methoxytyramine, and their respective deaminated metabolites, 3, 4-dihydroxyphenylacetic acid and homovanillic acid. It is concluded that conversion of deprenyl to amphetamine and methamphetamine may contribute to some of the therapeutic benefits of deprenyl.

Gas chromatographic-mass spectrometric analysis of amine metabolites in urine

An analytical method for the separation and identification of amine metabolites in human urine has been developed using a gas chromatograph-mass spectrometer-computer system. The sample preparation consists of organic solvent extraction, adsorption on a cation-exchange resin, evaporation, and acylation. N-3-Hydroxypropyl-1, 4-diaminobutane was identified for the first time in urine. Methylguanidine, guanidine, putrescine, cadaverine, p-tyramine, 3-methoxytyramine, spermidine, and spermine were detected in normal urine with good gas chromatographic separation.

A study on the acute effect of amphetamine on the urinary excretion of biogenic amines and metabolites in monkeys

1 The effects of an acute dose (3 mg/kg) of amphetamine on the urinary excretion of phenylethylamine (PEA), p-tyramine, their metabolites, catecholamine metabolites and p-hydroxymandelic acid, a major metabolite of p-octopamine were evaluated in the monkey. Amphetamine excretion was also measured. 2 Amphetamine was slowly eliminated from the body, being found in the urine at least six days after administration. 3 Amphetamine increased the excretion of PEA and decreased that of its major metabolite, phenylacetic acid (PAA). This pattern of changes is similar to that previously found in the urine of chronic schizophrenics. 4 The excretion of the dopamine metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC) was markedly reduced, that of vanilmandelic acid (VMA) remained unchanged while 3-methoxy-4-hydroxyphenylglycol (MHPG) was increased on the day of drug administration and persisted for at least a further six days. A similar extended effect on the excretion of p-hydroxymandelic acid (it was reduced) was also observed. 5 The excretion of p-tyramine but not its metabolite, p-hydroxyphenylacetic acid, was decreased by amphetamine during treatment and returned to normal levels six days later. 6 From the results obtained, it was concluded that amphetamine effects on behaviour cannot exclusively be attributed to its influence on catecholamines and that other biogenic amines may be involved. 7 Since PEA elicits many behavioural changes similar to those seen with amphetamine, and since amphetamine increases PEA excretion, we suggest that amphetamine may exert some of its behavioural responses through the release of PEA.

Detection of urinary primary amines through negative chemical ionization mass spectrometry of fluorescamine derivatives

We report the successful detection of urinary biogenic amines by a procedure which involves isolation of the amines on CG-50 cation exchange resin, derivatization of the amines with fluorescamine while on the resin, followed by direct probe negative chemical ionization mass spectrometry screening of the resin extract. This isolation procedure allowed the detection of tyramine, octopamine, normetanephrine, 3-methoxytyramine and a variety of aliphatic amines. Norepinephrine, dopamine and serotonin were chemically reactive under these conditions and were not detectable at physiological concentrations.

Urinary acid metabolites of biogenic amines in schizophrenic patients

A hypothesis is presented that only pure type B monoamine oxidase (MAO) amine substrates and their oxidized metabolites should be altered in mental patients, especially paranoid chronic schizophrenics. If urinary pH is rigorously controlled, it is predicted that 24-hour urinary amine levels (free and total) of pure type B MAO substrates will be elevated and their corresponding acid metabolites reduced, especially under excess substrate conditions in vivo. The usual 50 percent decrease in platelet MAO, which is reported to be in some schizophrenic patients in vitro, should especially show biochemical functional deficits in vivo when the organism is stressed with a suitable amine or amino acid substrate given as a diagnostic load. Such an approach amy be useful in demonstrating a functional biochemical deficit and the biological significance of low platelet MAO activity (a type B MAO) seen in some psychiatric patients.