Application of Magnetic Core-Shell Imprinted Nanoconjugates for the Analysis of Hordenine in Human Plasma-Preliminary Data on Pharmacokinetic Study after Oral Administration

In this paper, we developed and validated a new analytical method to determine the pharmacokinetic profile of hordenine in plasma samples of human volunteers after oral administration of hordenine-rich dietary supplements. For this purpose, a magnetic molecularly imprinted sorbent was fabricated and characterized. The application of a magnetic susceptible material facilitates pretreatment step while working with a highly complex sample, reducing time and costs. An optimized, fast, and reliable separation step was combined with liquid chromatography tandem mass spectrometry, providing an analytical method for analysis of hordenine in human plasma after dietary supplement intake. The method was validated (lower limit of quantification of 0.05 μg/L), enabling the pharmacokinetic profile of hordenine to be determined. The highest concentration of hordenine was noted after 65 ± 14 min, reaching the value of 16.4 ± 7.8 μg/L. The average t1/2 was 54 ± 19 min. The apparent volume of distribution was 6000 ± 2600 L (66 ± 24 L/kg when adjusted for weight).

Absorption, Biokinetics, and Metabolism of the Dopamine D2 Receptor Agonist Hordenine (N,N-Dimethyltyramine) after Beer Consumption in Humans

Hordenine, a natural constituent of germinated barley, is a biased agonist of the dopamine D2 receptor. This pilot study investigated the biokinetics of hordenine and its metabolites in four volunteers consuming beer equal to 0.075 mg hordenine/kg body weight. A new ultrahigh-performance liquid chromatography method coupled to electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) method determined maximum plasma concentrations of 12.0-17.3 nM free hordenine after 0-60 min. Hordenine phase-II metabolism was first dominated by sulfation, but later by glucuronidation. The elimination half-lives in plasma were 52.7-66.4 min for free hordenine and about 60/80 min longer for hordenine sulfate and hordenine glucuronide. Urinary excretion peaked 2-3.5 h after consumption and accumulated to 3.78 μmol within 24 h, corresponding to 9.9% of the ingested dose. The observed hordenine levels in plasma seem too low to provoke direct interaction with the dopamine D2 receptor related to food reward, but synergistic or additive effects with alcohol or N-methyltyramine may occur.

Abnormal Platelet Trace Amine Profiles in Migraine With and Without Aura

Trace amines, including tyramine, octopamine and synephrine, are closely related to classic biogenic amines. In one study, where these substances were found elevated in plasma of migraineurs, it was hypothesized that trace amine metabolism is deranged in migraine. To confirm these findings, we studied, using a multichannel electrochemical high-performance liquid chromatography system, the concentrations of trace amines in platelets of migraine without aura (MoA) and migraine with aura (MA) patients in headache-free period, compared with controls. Platelet concentrations of trace amines, although elevated in both migraine types, showed a different profile in MoA and MA. Octopamine was significantly higher in MoA sufferers (0.69 ± 0.43 ng/108 platelets) compared with both control subjects (0.22 ± 0.16 ng/108 platelets) and MA patients (0.39 ± 0.37 ng/108 platelets). Synephrine was significantly higher in MA patients (0.72 ± 0.44 ng/108 platelets) with respect to both controls (0.33 ± 0.25 ng/108 platelets) and MoA sufferers (0.37 ± 0.29 ng/108 platelets). These results strengthen the hypothesis that tyrosine metabolism is deranged in migraine and may participate in its pathophysiology.

Is migraine a risk factor for the occurrence of eating disorders? Prevalence and biochemical evidences

The eating disorders (ED), anorexia nervosa (AN) and bulimia nervosa (BN), are severe psychiatric and somatic conditions occurring mainly in young woman. Although the aetiology is largely unknown, same evidences suggest that biological and psychological factors play a relevant role in the pathogenesis, along with monoamine, indole and same hypothalamic hormonal dysfunctions. Migraine is characterized by similar metabolic and psychological anomalies suggesting that a possible relationship exists between the two pathological conditions. To understand the possible relationship between migraine and ED, we have investigated the prevalence of migraine and the other primary headaches in a large group of AN and BN patients. In addition, we have studied the role of tyrosine metabolism in the same group of AN and BN young woman sufferers. In particular, we measured plasma levels of elusive amines: tyramine (Tyr) and octopamine (Oct) and catecholamines: noradrenalin (NE), dopamine (DA). The results of this study show that the prevalence of migraine in the woman affected by ED is very high (<75 %). The levels of Tyr and DA were higher and levels of NE were lower in the ED patients in respect to the control subjects. These biochemical findings suggest that abnormalities of limbic and hypothalamic circuitries play a role in the pathogenesis of ED. The very high prevalence of migraine in our group of ED sufferers and the biochemical profile of migraine, similar to that of ED patients shown in this study, suggest that migraine may constitute a risk factor for the occurrence of ED in young females. This hypothesis is supported by the onset of migraine attacks that initiated, in the majority of the patients, before the occurrence of ED symptoms.

The role of tyrosine metabolism in the pathogenesis of chronic migraine

OBJECTIVE

The pathogenesis of chronic migraine (CM) remains largely unknown. We hypothesized that anomalies of tyrosine metabolism, found in migraine without aura (MwwA) patients, play an important role in the transformation of MwwA into CM, since the increase in the number of MwwA attacks is the most predisposing factor for the occurrence of CM.

METHODS

To test our hypothesis we measured the plasma levels of dopamine (DA), noradrenaline (NE) and trace amines, including tyramine (TYR) and octopamine (OCT), in a group of 73 patients with CM, 13 patients with chronic tension-type headache (CTTH) and 37 controls followed in the Headache Centers of the Neurology Departments of Asti, Milan and Vicenza hospitals in Italy.

RESULTS

The plasma levels of DA and NE were several-fold higher in CM patients compared with control subjects ( P  > 0.001). The plasma levels of TYR were also extremely elevated ( P  > 0.001); furthermore, these levels progressively increased with the duration of the CM.

CONCLUSIONS

Our data support the hypothesis that altered tyrosine metabolism plays an important role in the pathogenesis of CM. The high plasma levels of TYR, a potent agonist of the trace amine associated receptors type 1 (TAAR1), may ultimately down-regulate this receptor because of loss of inhibitory presynaptic regulation, therein resulting in uncontrolled neurotransmitter release. This may produce functional metabolic consequences in the synaptic clefts of the pain matrix implicated in CM.

Dietary fructan carbohydrate increases amine production in the equine large intestine: implications for pasture-associated laminitis

Pasture-induced laminitis in the horse is associated with the overconsumption of fermentable carbohydrate, in the form of simple sugars, fructans, or starch. The fermentation of carbohydrate in the cecum and large intestine results in the production of lactic acid and other toxins or "laminitis trigger factors." Vasoactive amines have been suggested as possible initiating factors. The aim of this study was to feed a commercially available form of fructan carbohydrate (inulin, 3 g/kg of BW per day) to normal ponies and to ponies predisposed to laminitis, to mimic a change from a basal hay diet to lush spring-summer pasture. Five normal and 6 laminitis-prone, native-breed ponies were acclimated to a basal hay diet before the inclusion of inulin and chopped dried grass. Blood samples, fecal samples, and foot temperature measurements were taken throughout the study. Amines were measured in the feces and plasma by HPLC and liquid chromatography-mass spectrometry, respectively. The pH of the fecal samples decreased from 6.89 +/- 0.11 on the hay diet to a minimum of 6.18 +/- 0.11 with the addition of inulin (P <0.05). An increase was observed in the fecal concentrations of a number of amines, including tryptamine (2.5-fold increase, P <0.05) and tyramine (2-fold increase, P <0.05). No changes were noted in plasma amine concentrations or plasma D- or L-lactate, indicating that there may be a threshold of hindgut pH change before mucosal damage can result in the release of these factors into the circulation. No differences in pH or any of the measured compounds were observed between the group of normal ponies and those predisposed to laminitis. This indicates that differences in the intestinal microflora do not account for this predisposition. However, the results from this study indicate that moderate increases in dietary fructan carbohydrate can produce increases in bacterial fermentation products and other compounds in the large intestine, which may be relevant to the pathogenesis of acute laminitis in ponies on pasture.

Quantitation of clovamide-type phenylpropenoic acid amides in cells and plasma using high-performance liquid chromatography with a coulometric electrochemical detector

A high-performance liquid chromatography (HPLC) method was developed for measuring the concentrations of clovamide-type phenylpropenoic acid amides (N-caffeoyldopamine and N-caffeoyltyramine) in cell and plasma samples. The separation was performed on a Nova-Pak C18 column using an isocratic buffer with a coulometric electrochemical detector with four electrode channels. Using the HPLC method, N-caffeoyldopamine and N-caffeoyltyramine could be detected with good peak resolutions at respective retention times (4 and 6.4 min). The calibration curves were linear over the ranges (0.1 and 100 microM), and their lower limit of detection was as little as 100 fmol. For quantifying N-caffeoyldopamine and N-caffeoyltyramine in cell and plasma samples, the samples were extracted by extraction methods with more than 95% recoveries. After extraction, the amides were detected with the same sensitivity, peak resolutions, and retention times. Using this method, plasma concentrations of N-caffeoyltyramine were determined in blood samples collected at 12, 24, 30, 36, 48, 60, and 75 min after the oral administrations of N-caffeoyltyramine (0.5 mg and 2 mg/30 g body weight). This HPLC method with an electrochemical detector is the first reported method able to quantify N-caffeoyldopamine and N-caffeoyltyramine in biological samples with excellent detection limits, peak resolutions, discrete retention times, and consistent reproducibility.

Elevated levels of circulating trace amines in primary headaches

BACKGROUND

Trace amines, including tyramine, octopamine, and synephrine, are closely related to classic biogenic amines. They have been hypothesized to promote migraines and other types of primary headaches, but there is no direct evidence supporting this hypothesis.

METHODS

Using a multichannel electrochemical high-performance liquid chromatography system, the authors evaluated whether changes in circulating trace amines occur in subjects with migraine (with or without aura) during headache-free periods as well as in patients with cluster headache (CH) during the remission and active phases as compared with healthy control subjects.

RESULTS

Plasma levels of all trace amines were significantly higher in CH patients, in both the remission and the active phases, when compared with control subjects or subjects with migraine. In addition, intraplatelet levels of octopamine, synephrine, and tyramine were higher in CH patients than in control subjects. In migraine patients, plasma levels of octopamine and synephrine were higher compared with controls, although in migraine with aura, the difference was not significant.

CONCLUSIONS

Whereas the elevation of plasma trace amine levels in both migraine and CH supports the hypothesis that disorders of biogenic amine metabolism may be a characteristic biochemical trait in primary headache sufferers, the observation that such alterations are more prominent in patients with CH than migraine patients suggests that they may reflect sympathetic or hypothalamic dysfunction.

Seasonal changes in plasma concentrations of cecum-derived amines in clinically normal ponies and ponies predisposed to laminitis

OBJECTIVE

To measure concentrations of amines formed in the cecum of clinically normal ponies, determine amine concentrations in plasma samples collected in spring and winter, and compare concentrations of amines and serotonin in plasma samples obtained from clinically normal ponies and ponies predisposed to laminitis.

SAMPLE POPULATION

Cecal contents obtained from 10 ponies euthanatized at an abattoir and blood samples obtained from 42 adult ponies.

PROCEDURE

Cecal contents were assayed for amines by high-performance liquid chromatography (HPLC). Blood samples were collected at various times of the year from 20 ponies predisposed to acute laminitis and 22 clinically normal ponies. Plasma serotonin concentration was measured by HPLC, and tryptamine (TRP), tyramine (TYR), phenylethylamine (PEA), and isoamylamine (IAA) were measured by liquid chromatography-mass spectrometry.

RESULTS

15 amines were identified in cecal contents. Plasma TRP, TYR, PEA, and IAA concentrations ranged from 10pM to 100nM in both groups of ponies. Plasma concentrations of serotonin or other amines did not differ between clinically normal ponies and those predisposed to laminitis; however, significantly higher concentrations of TRP, PEA, and IAA were found in samples obtained in the spring, compared with winter samples.

CONCLUSIONS AND CLINICAL RELEVANCE

Various amines are found in the cecum of ponies, several of which can be detected in the plasma. Concentrations increase significantly in the spring and may reach concentrations close to the threshold for causing vasoconstriction. Release of amines from the cecum into the systemic circulation may contribute to hemodynamic disturbances in horses and ponies with acute laminitis.

HPLC electrochemical detection of trace amines in human plasma and platelets and expression of mRNA transcripts of trace amine receptors in circulating leukocytes

We evaluated, using a multi-channel electrochemical HPLC system, whether trace amines are detectable in plasma and platelets of healthy control subjects. To this end, levels of tyramine, octopamine and synephrine were assessed in samples obtained from eight males and eight females, age matched and free from drugs. In plasma, octopamine was detectable in all subjects, synephrine in 15 and tyramine in six out of 16 subjects. Likewise, detectable levels of octopamine together with synephrine were, in contrast to tyramine, found within platelets of most individuals. Intracellular levels of the amines significantly diminished following platelet activation (ADP or collagen). In addition, circulating leukocytes from these same subjects are herein shown to express mRNA transcripts for the recently discovered 'trace amine receptors' (TAR-1, -3, -4 and -5). Thus, although baseline plasma levels of octopamine tyramine or synephrine may vary among healthy individuals, the observation that platelets store and actively release these trace amines suggests that they may be effectors involved in platelet-mediated signaling events in the bloodstream.

Tyramine pharmacokinetics and reduced bioavailability with food

Tyramine challenge studies have demonstrated that it requires approximately twice the amount of tyramine administered with a meal compared to administration after a fast to elicit the same effect, suggesting a reduction in bioavailability of tyramine when administered with food. The pharmacokinetics of tyramine when administered in a fasted versus a fed state were studied. A single 200-mg dose of tyramine was administered orally to healthy subjects both after an overnight fast and during a meal. Systemic exposure to tyramine was reduced by 53% (p < 0.05), and the maximum concentration of tyramine was reduced by 72% (p < 0.05) when the dose was administered during a meal. Tyramine maximum serum concentration was observed between 20 minutes and 1 hour when the dose was administered after an overnight fast and appeared to be delayed and/or prolonged by administration during a meal. Tyramine oral clearance was 135 +/- 55.4 L/min, maximum observed serum concentration was 37.7 +/- 26.01 ng/mL, and tyramine elimination half-life was 0.533 (range: 0.330-0.668) hours after administration to fasted subjects. Tyramine bioavailability was significantly reduced when administered with a meal compared to after a fast. The results suggest that larger amounts of dietary tyramine will be required to induce a pressor response equivalent to that following encapsulated tyramine administered in the fasted state.

Stacking for nonaqueous capillary electrophoresis

Nonaqueous capillary electrophoresis (NACE) is a useful mode in CE for separation and quantification of hydrophobic compounds. However, because of the low conductivity of most of the organic solutions, stacking is not used often in this technique and the sample volume is very limited. As a result of the small sample volume, the detection limits are poor. Furthermore, NACE is affected greatly by the presence of salts in the sample. Here, we show that transient isotachophoresis (t-ITP) can be used easily in this type of electrophoresis to enhance the detection limits and also to reverse the deleterious effects of salts in the sample. Several factors, which affect the stacking in this type of electrophoresis, are described. For example, the presence of salts in the organic solvent, type of sample introduction, and the solvent for the terminating ion were all found to have profound effects on the degree of concentration. Furthermore, the separation time can be shortened by t-ITP.

Analysis and prediction of absorption profile including hepatic first-pass metabolism of N-methyltyramine, a potent stimulant of gastrin release present in beer, after oral ingestion in rats by gastrointestinal-transit-absorption model

The prediction method for the plasma concentration-time profile of N-methyltyramine (NMT), a potent stimulant of gastrin release present in beer after oral ingestion in rats was examined using the previously developed Gastrointestinal (GI)-Transit-Absorption Model, with the addition of a process of hepatic first-pass metabolism. Phenol red was used as a nonabsorbable marker for estimation of the GI transit rate constant for eight segments in the GI tract. The first order absorption rate constant for each segment was estimated by means of a conventional in situ closed loop method. The results of in situ absorption experiments showed that NMT is well absorbed in the small intestine, especially in the duodenum and jejunum. Using the GI-Transit-Absorption Model, it was demonstrated that more than 90% of orally ingested NMT is absorbed in the small intestine, and that the substantial absorption site for NMT in vivo is the lower jejunum and the ileum. However, the observed bioavailability was only 39.0%. The in vitro metabolism study clarified that NMT is metabolized in the liver, but not in the small-intestinal mucosa. With the hepatic intrinsic clearance value (2.0 liters/h) calculated from the rate of metabolism in vitro, the hepatic availability was estimated to be 0.510 on the basis of a well stirred model, which was validated by two other methods to calculate the hepatic availability of NMT. The plasma concentration-time curve and bioavailability of NMT after oral ingestion were well predicted by the GI-Transit-Absorption Model with the hepatic first-pass metabolism process.

Agonistic behaviour and biogenic amines in shore crabs Carcinus maenas

To investigate the role of certain neurohormones in agonistic behaviour, fights were staged between pairs of size-matched male shore crabs Carcinus maenas, and blood samples were taken immediately after the contests had been resolved. Samples were also taken from these crabs at rest (before and after fighting) and after walking on a treadmill. A control group of crabs also had samples taken on each experimental day. Concentrations of tyramine, dopamine, octopamine, serotonin (5-HT) and norepinephrine were determined in each blood sample using a gas chromatography/mass spectrometry (GC-MS) system. Norepinephrine was not detectable in any of the samples, but the standards were recovered. Tyramine values were not significantly different between the control group and the fought group, so tyramine does not appear to be important in agonistic behaviour. A comparison between the control and fought groups shows that fighting had an effect on the concentrations of octopamine, dopamine and 5-HT, but exercise only had an effect on octopamine levels, which showed a reduction from resting values in both winners and losers. Resting and post-fight concentrations of octopamine, dopamine and 5-HT were higher in winners than in losers. 5-HT concentration increased in the blood of fought crabs from resting values, whereas dopamine concentration decreased. In winners, octopamine concentrations decreased from resting values, but in losers octopamine levels increased from resting concentrations. The escalatory behaviour or intensity of fighting performed by winners and losers was related to dopamine levels but not to those of octopamine or 5-HT. Therefore, there appears to be a link between relative concentrations of these three amines (dopamine, octopamine and 5-HT) and fighting ability; the effects are not simply a result of activity. The better competitors have higher concentrations of these three amines at rest and after fighting.

Catecholamine handling in the porcine heart: a microdialysis approach

Experimental findings suggest a pronounced concentration gradient of norepinephrine (NE) between the intravascular and interstitial compartments of the heart, compatible with an active neuronal reuptake (U1) and/or an endothelial barrier. Using the microdialysis technique in eight anesthetized pigs, we investigated this NE gradient, both under baseline conditions and during increments in either systemic or myocardial interstitial fluid (MIF) NE concentration. At steady state, baseline MIF NE (0.9 +/- 0.1 nmol/l) was higher than arterial NE (0.3 +/- 0.1 nmol/l) but was not different from coronary venous NE (1.5 +/- 0.3 nmol/l). Local U1 inhibition raised MIF NE concentration to 6.5 +/- 0.9 nmol/l. During intravenous NE infusions (0.6 and 1.8 nmol. kg(-1). min(-1)), the fractional removal of NE by the myocardium was 79 +/- 4% to 69 +/- 3%, depending on the infusion rate. Despite this extensive removal, the quotient of changes in MIF and arterial concentration (DeltaMIF/DeltaA ratio) for NE were only 0.10 +/- 0.02 for the lower infusion rate and 0.11 +/- 0.01 for the higher infusion rate, whereas U1 blockade caused the DeltaMIF/DeltaA ratio to rise to 0.21 +/- 0.03 and 0.36 +/- 0.05, respectively. From the differences in DeltaMIF/DeltaA ratios with and without U1 inhibition, we calculated that 67 +/- 5% of MIF NE is removed by U1. Intracoronary infusion of tyramine (154 nmol. kg(-1). min(-1)) caused a 15-fold increase in MIF NE concentration. This pronounced increase was paralleled by a comparable increase of NE in the coronary vein. We conclude that U1 and extraneuronal uptake, and not an endothelial barrier, are the principal mechanisms underlying the concentration gradient of NE between the interstitial and intravascular compartments in the porcine heart.

Pressor effect of oral tyramine during treatment with befloxatone, a new reversible monoamine oxidase-A inhibitor, in healthy subjects

The interaction between tyramine and befloxatone, a new selective, reversible monoamine oxidase-A (MAO-A) inhibitor, was studied in a single-blind, parallel-group study in 30 healthy male volunteers whose fasting tyramine 30 dose (Tyr30) was 400 or 600 mg. Each subject completed a placebo run-in period followed by a befloxatone period. Befloxatone was given in repeated doses according to one of three regimens: befloxatone 20 mg once daily at the end of a meal rich in tyramine or befloxatone 10 or 20 mg twice daily 2 hours before a meal rich in tyramine. Subjects were given increasing daily doses of tyramine mixed with the meal, until a systolic blood pressure increase of at least 30 mm Hg was achieved (Tyr30). The mean Tyr30 decreased from 1220 mg (range, 600-1800 mg) during placebo to 290 mg (range, 150-500 mg) during befloxatone 20 mg once daily, 250 mg (range, 100-300) during befloxatone 10 mg twice daily, and 155 mg (range, 100-250 mg) during befloxatone 20 mg twice daily; corresponding to a potentiation factor of 5.2-, 6.5-, and 7.9-fold, respectively. The extent and the duration of the systolic blood pressure increase did not significantly differ between the placebo and the befloxatone regimens, except for a longer duration with the 20-mg twice daily regimen. These results are similar to those reported with the therapeutic dosage of other selective MAO-A inhibitors. They suggest that there would be little risk of hypertensive crisis in patients treated in clinical studies with befloxatone, and thus dietary restrictions appear to be unnecessary when the drug is given in a regimen of up to 20-mg once daily after meals.

Kinetics and metabolism of p-tyramine during monoamine oxidase inhibition by mofegiline

The effects of monoamine oxidase B (MAO-B) inhibition by mofegiline on the pharmacokinetics of p-tyramine and its major metabolite, p-hydroxyphenylacetic acid, were investigated in 24 healthy male volunteers. p-Tyramine doses were administered before and after a 14-day treatment period of 1, 12, or 24 mg mofegiline or placebo. Normalized p-tyramine for area under the plasma concentration-time curve after treatment were not significantly different from their respective before-treatment values for any of the dose groups. The relative bioavailability of p-tyramine after treatment was not significantly different from before treatment, although a tendency to a greater bioavailability was seen with the 12 and 24 mg doses. There were no significant differences between pharmacokinetic parameters for p-hydroxyphenylacetic acid. The data suggest that mofegiline maintains its selectivity for MAO-B in the intestine and liver at doses up to and including 24 mg. Therefore these doses would not be expected to be associated with the hypertensive crises normally associated with the "cheese effect."

Analysis of biogenic amines in plasma of hypertensive patients and a control group

Procedures were developed for the determination of 17 circulating amines using gas chromatography-negative ion chemical ionisation mass spectrometry. The amines were quantified against their appropriate deuterated isotopomers. The mean concentrations and ranges of catecholamines and trace amines were high compared with previous studies. In comparison with nonhypertensives, plasma from hypertensives had higher concentrations of the following amines: noradrenaline (t = 4.0%); normetanephrine (t = 6.1%) and metanephrine (t = 1.9%). There were no significant differences between 5HT levels in plasma from hypertensives and controls. The following trace amines could be detected in variable amounts in plasma: p-tyramine, m-tyramine, p-octopamine, m-octopamine, p-synephrine, m-synephrine, and salsolinol. The trace amines melatonin, N-acetyl 5HT, tryptamine, 6-hydroxymelatonin and 5-methoxytryptamine could not be detected in plasma with limits of detection lying in the range 20-100 pg ml-1.

Determination of regional distributions of phenylethylamine and meta- and para-tyramine in rat brain regions and presence in human and dog plasma by an ultra-sensitive negative chemical ion gas chromatography-mass spectrometric (NCI-GC-MS) method

Using a new ultrasensitive method the trace biogenic amines, phenylethylamine, meta-tyramine and para-tyramine have been quantitated in brain regions obtained from a single rat. Phenylethylamine concentrations in ng/g wet tissue (mean +/- std. error) were as follows: caudate 2.71 +/- 0.73, hypothalamus 0.45 +/- 0.15, cerebellum 0.09 +/- 0.02, olfactory bulb 0.35 +/- 0.11, stem 0.13 +/- 0.03, hippocampus 0.20 +/- 0.11, cortex 0.69 +/- 0.13 and the rest (remainder of the brain) 2.81 +/- 0.41. Mean whole brain was 1.23 +/- 0.19 ng/g, in agreement with previous measurements. meta-Tyramine concentrations (ng/g) were: caudate 2.69 +/- 0.19, hypothalamus 0.32 +/- 0.16, cerebellum 0.07 +/- 0.04, olfactory bulb 0.09 +/- 0.04, stem 0.04 +/- 0.01, hippocampus 0.07 +/- 0.02, cortex 0.18 +/- 0.15 and the rest 0.15 +/- 0.06, with a mean whole brain value of 0.26 +/- 0.05 ng/g and para-tyramine concentrations were: caudate 8.99 +/- 1.60, hypothalamus 0.93 +/- 0.13, cerebellum 0.78 +/- 0.27, olfactory bulb 0.70 +/- 0.13, stem 0.90 +/- 0.36, hippocampus 0.40 +/- 0.06, cortex 1.78 +/- 0.28 and the rest 2.38 +/- 0.12 and mean whole brain was 1.90 +/- 0.25 ng/g. In human plasma the concentrations of the three amines were found to be 31.3 +/- 3.4 pg/ml, 5.3 +/- 1.6 pg/ml and 66.0 +/- 9.9 pg/ml respectively and in dog blood 95.3 +/- 4.6 pg/ml, 24.0 +/- 7.6 pg/ml and 486 +/- 43 pg/ml respectively. When monoamine oxidase inhibitors were added to the blood immediately after collection there were no significant increases in the amine levels indicating that MAO-B is not present in plasma in significant quantities.

Hepatic removal of 125I-DLT gelatin after burn injury: a model of soluble collagenous debris that interacts with plasma fibronectin

The decline of plasma fibronectin after surgery, trauma, and burn, as well as during severe sepsis after injury, appears to limit hepatic Kupffer cell phagocytic activity. Intravenous infusion of gelatin-coated particles to simulate blood-borne particulate collagenous tissue debris in the circulation after injury also depletes plasma fibronectin. We used soluble gelatin conjugated with 125I-labeled dilactitol tyramine (DLT-gelatin) as a model of soluble collagenous tissue debris. We studied its blood clearance as well as organ localization in normal and postburn rats. Fibronectin-deficient plasma harvested early after burn exhibited limited ability to support in vitro phagocytic uptake of the gelatinized microparticles by Kupffer cells in liver tissue from normal rats. However, Kupffer cells in liver tissue from normal and postburn rats phagocytized the test particles at a normal rate when incubated in normal plasma. The DLT-gelatin ligand bound to fibronectin in a dose-dependent manner as verified by its capture with anti-fibronectin coated plastic wells when coincubated with purified fibronectin. By gel filtration chromatography, the binding of fibronectin with the DLT-gelatin ligand was readily detected, resulting in the formation of a high-molecular-weight complex. In normal animals the plasma clearance and liver localization of 125I-DLT-gelatin was competitively inhibited by infusion of excess nonradioactive gelatin. The blood clearance and liver localization of the soluble gelatin ligand were also impaired after burn injury during periods of fibronectin deficiency similarly to the pattern observed with gelatin-coated microparticles. By autoradiography, the cellular site for the uptake of the 125I-DLT-gelatin was primarily but not exclusively hepatic Kupffer cells; 125I-DLT-asialofetuin and 125I-DLT-ovalbumin were removed by hepatocytes and sinusoidal endothelial cells, respectively. Thus, gelatin conjugated with 125I-DLT can be used to simulate blood-borne soluble collagenous tissue debris after burn. It rapidly binds to plasma fibronectin before its hepatic Kupffer cell removal, and its blood clearance is markedly delayed after burn injury during periods of plasma fibronectin deficiency.

Pharmacokinetic and pharmacodynamic interaction between toloxatone, a new reversible monoamine oxidase-A inhibitor, and oral tyramine in healthy subjects

We examined the influence of toloxatone, a new reversible monoamine oxidase-A inhibitor used in the treatment of depression, on tyramine-induced pressor effect in healthy volunteers. The maximum increase in systolic blood pressure produced by four single oral doses of tyramine administered during a meal and ranging from 100 mg to 800 mg was compared during repeated (3 to 5 days) administration of placebo, 200 mg toloxatone three times a day and 400 mg toloxatone three times a day in a single-blind, three-period crossover study. Toloxatone by itself had no significant influence on blood pressure. During administration of toloxatone, no significant increase in tyramine-induced increase in systolic blood pressure was observed for tyramine doses of 200 mg or less that are consistently higher than those associated with normal food intake. However, toloxatone increased the tyramine-induced increase in blood pressure after 400 mg tyramine (400 mg toloxatone three times a day) and 800 mg tyramine (200 mg toloxatone three times a day and 400 mg toloxatone three times a day). This pharmacodynamic interaction could be explained by an increase in tyramine systemic bioavailability in the presence of toloxatone. It is concluded that interaction between tyramine in meals and toloxatone is unlikely to occur in patients after long-term administration of the drug at therapeutic dosages.

Inulin-125I-tyramine, an improved residualizing label for studies on sites of catabolism of circulating proteins

Residualizing labels for protein, such as dilactitol-125I-tyramine (125I-DLT) and cellobiitol-125I-tyramine, have been used to identify the tissue and cellular sites of catabolism of long-lived plasma proteins, such as albumin, immunoglobulins, and lipoproteins. The radioactive degradation products formed from labeled proteins are relatively large, hydrophilic, resistant to lysosomal hydrolases, and accumulate in lysosomes in the cells involved in degradation of the carrier protein. However, the gradual loss of the catabolites from cells (t1/2 approximately 2 days) has limited the usefulness of residualizing labels in studies on longer lived proteins. We describe here a higher molecular weight (Mr approximately 5000), more efficient residualizing glycoconjugate label, inulin-125I-tyramine (125I-InTn). Attachment of 125I-InTn had no effect on the plasma half-life or tissue sites of catabolism of asialofetuin, fetuin, or rat serum albumin in the rat. The half-life for hepatic retention of degradation products from 125I-InTn-labeled asialofetuin was 5 days, compared to 2.3 days for 125I-DLT-labeled asialofetuin. The whole body half-lives for radioactivity from 125I-InTn-, 125I-DLT-, and 125I-labeled rat serum albumin were 7.5, 4.3, and 2.2 days, respectively. The tissue distribution of degradation products from 125I-InTn-labeled proteins agreed with results of previous studies using 125I-DLT, except that a greater fraction of total degradation products was recovered in tissues. Kinetic analyses indicated that the average half-life for retention of 125I-InTn degradation products in tissues is approximately 5 days and suggested that in vivo there are both slow and rapid routes for release of degradation products from cells. Overall, these experiments indicate that 125I-InTn should provide greater sensitivity and more accurate quantitative information on the sites of catabolism of long-lived circulating proteins in vivo.

Effect of moclobemide, a new reversible monoamine oxidase inhibitor, on absorption and pressor effect of tyramine

We determined in healthy subjects the pressor effect and the plasma level of free tyramine in response to intravenous and oral tyramine doses before and after therapeutic doses (3 X 100 mg/day) of moclobemide, a new reversible, preferential type A monoamine oxidase (MAO) inhibitor. In fasting subjects moclobemide increased the pressor effect of intravenously and orally administered tyramine; the tyramine dose-pressor curve was shifted to the left by factors of 2.4 and 4.1, respectively. No increase in systolic blood pressure occurred at free plasma tyramine concentrations lower than 70 ng/ml before, and 20 ng/ml after, moclobemide. Peak plasma tyramine concentrations increased dose-dependently after oral tyramine; after moclobemide similar peak plasma concentrations of tyramine were obtained with 2.6 times smaller doses of tyramine. Thus, the potentiation by moclobemide of the pressor effect of oral tyramine appears to be due to inhibition of tyramine first-pass metabolism, as well as to inhibition of tyramine catabolism by MAO within adrenergic nerve terminals. The peak concentrations of free tyramine in plasma and the concomitant increase of systolic blood pressure were significantly (p less than 0.01) smaller when tyramine was administered with a meal (before or after moclobemide) than when given with tap water. We conclude that at doses of 3 X 100 mg/day moclobemide induces only a mild potentiation of the pressor effect of tyramine. This potentiation is virtually absent under natural conditions when tyramine is given with a meal.

Phenylalanine: total amino acid ratio in 45 burn patients

In 45 burn patients serum amino acids together with liver enzymes and other serum parameters were determined. Phe levels, Phe:Tyr and Phe:TAA ratios were correlated with the clinical course of the patient's condition. Based on empirical data, an increase in the Phe:TAA ratio of over 3% was found to be the best indicator of a critical period in the clinical course. An increase in the Phe:TAA ratio above 3% accompanied the signs of sepsis. If the patient recovered, the ratio decreased. Ratios which kept constant or even increased--indicating a possible fatal clinical outcome--were found to be alarming. In our experience Phe levels or Phe:Tyr ratios did not have indicative functions.

The effects of amiflamine, a reversible MAO-A inhibitor, on the first pass metabolism of tyramine in dog intestine

The effects of amiflamine on tyramine deamination were studied using isolated loops of intestine in anesthetized dogs. In the pretreatment experiment, dogs were dosed with amiflamine (3.5 mg/kg/day) once daily for 3 days, with the study being carried out 3 hr after the final dose. [14C] Tyramine (50 mg and 50 microCi) in 10 ml of normal saline was introduced into the isolated loops of gut, and tyramine and p-hydroxyphenylacetic acid in the venous blood were separated by HPLC and measured by scintillation spectrometry. In the untreated dogs, approximately 15% of the tyramine passed through the gut wall unchanged. When tyramine and amiflamine (0.06 to 3.5 mg/kg) were administered simultaneously to the gut loop, about 27 to 65% of the tyramine passed through the gut wall unchanged. On the contrary, after pretreatment with amiflamine for 3 days, percentage of tyramine passing through the gut wall was not increased in comparison with the control. These results suggest that pretreatment with amiflamine does not produce drug concentrations in the lining cells of the gut sufficient to effectively inhibit the deamination of oral tyramine, which is administered at least 3 hr after the final dose of amiflamine.

High-performance liquid chromatography with amperometric determination of plasma tyramine

A method for the measurement of tyramine in human plasma is described. It is based on tetraphenylboron ion-pair extraction and reversed-phase ion-pairing liquid chromatography with amperometric detection. Tyramine can be reliably measured in the range 5-200 ng/ml with an absolute limit of detection of 0.50 ng/ml at a signal-to-noise ratio of 2.0. Correction for variable recovery is made by using a tritiated tyramine internal standard. This assay is suitable for studies on the bioavailability of ingested tyramine and should thus have a role in the development of safer monoamine oxidase inhibitor drugs.

Measurement of tyramine in human plasma, utilising ion-pair extraction and high-performance liquid chromatography with amperometric detection

An assay for plasma tyramine has been developed which uses ion-pair extraction, reversed-phase ion-pair high-performance liquid chromatography and amperometric detection. Tritiated tyramine is used as the internal standard. The method can measure down to 0.5 ng/ml of tyramine in 1 ml of human plasma and is thus suitable for monoamine oxidase inhibitor studies involving oral dosing with tyramine.

Tyrosine's pressor effect in hypotensive rats is not mediated by tyramine

Tyrosine, the amino acid precursor of catecholamines, increases blood pressure (BP) in hemorrhaged hypotensive rats. Since tyrosine may also be decarboxylated to form tyramine, which releases norepinephrine from sympathetic terminals, we tested the hypothesis that tyramine formation might mediate tyrosine's ability to increase BP. Three lines of evidence indicate that tyrosine does not act via this mechanism: pretreatment with reserpine blocked tyramine's but not tyrosine's pressor activity; pretreatment with hexamethonium left tyramine's effect intact but blocked the pressor response to tyrosine; and plasma tyramine did not increase after an hemodynamically-active dose of tyrosine (100 mg/kg).

Hypercatecholaminemia in Reye's syndrome

To evaluate the role of catecholamines in Reye's syndrome, a specific and sensitive radioenzymatic assay was used to study plasma and CSF concentration of dopamine, norepinephrine, and epinephrine in 14 patients with liver-biopsy-proven Reye's syndrome. The results (median and range) revealed significant (P less than .04, P less than .0024, and P less than .030, respectively) elevation in plasma dopamine (131, 0 to 1,193 pg/mL), norepinephrine (1,455, 20 to 5,271 pg/mL), and epinephrine (345, 7.6 to 2,504 pg/mL) at the onset of the disease when compared with the level of these neurotransmitters in a group of hospitalized patients without hepatic disorders. There was a positive correlation between plasma catecholamines and stage of coma on admission (r = .54 to .86; P less than .001 to .024). Furthermore, the concentration of dopamine, norepinephrine, and epinephrine in the CSF increased significantly during the development of cerebral edema in all patients with Reye's syndrome as compared with concentrations in a control population. Hypercatecholaminemia may contribute to the encephalopathy of Reye's syndrome.

Pressor sensitivity to tyramine in patients with headache: relationship to platelet monoamine oxidase and to dietary provocation

The pressor responses to oral and intravenous tyramine were not different from controls in migrainous patients with or without a history of attacks triggered by foods. However, patients who reported a dietary trigger were more likely to develop headache after tyramine administration than those without such a dietary history. Pressor responses to intravenous tyramine in patients with cluster headache were indistinguishable from controls. A group of five males with platelet monoamine oxidase activity one standard deviation or more below that of male controls required less intravenous tyramine to raise blood pressure by 30 mm Hg than males with monoamine oxidase levels within one standard deviation of the controls. This finding suggests that platelet monoamine oxidase activity to some extent reflects that of total body monoamine oxidase A plus B.

Platelet monoamine oxidase and erythrocyte catechol-o-methyltransferase activity in alcoholism and controlled abstinence

This study substantiates previous reports that low platelet monoamine oxidase (MAO) activity is associated with alcoholism. Catechol-o-methyltransferase (COMT) activity in erythrocytes of alcoholics did not differ from that of controls. In 20 male alcoholics low platelet MAO activity was found during the first 3 days after hospitalization. The MAO activity increased in the next 2 weeks of abstinence and then tended to decrease again.

Platelet monoamine oxidase activity and trace acid levels in plasma of agoraphobic patients

Platelet monoamine oxidase activity and plasma trace acid levels in 29 patients classified as agoraphobics was estimated. MAO activity towards p-tyramine and beta-phenylethylamine was found to be significantly higher in agoraphobics than in non-agoraphobic depressed patients and healthy controls. In addition plasma p-hydroxyphenylacetic acid levels were low in both agoraphobic and depressed patient groups. All patients were also assessed by Spielberger State Anxiety and the short form of the Beck Depression Inventory scales. No significant correlations could be found between platelet MAO activity or plasma trace acid levels and the psychological scores.

A study of the catabolism of trace amines in mentally disordered individuals with particular reference to agoraphobic patients with panic attacks

Platelet MAO activity toward several trace amine substrates and the plasma levels of some trace acids have been investigated. Compared to controls, the agoraphobic patients were found to have significantly increased MAO activity. The substrate specificity in some of the patients appeared to be altered. The plasma levels of p-HPA and m-HPA were significantly lower than those of the control groups.

Correlative relationship between biochemical activity and aggressive behaviour

Correlative relationships were investigated between biogenic trace amines and histories of violence among offenders incarcerated in two federal penitentiaries. Plasma levels of unconjugated (U) and conjugated (C) trace acids (PAA, mHPA and pHPA) and platelet MAO activity to the substrates PE, TRYP and TA were assessed. A pilot study (N = 26) revealed a lower activity of MAO to TRYP among violent offenders. The factor analytically derived scale, Prison Disturbance, correlated with mHPA (U) .77 (p less than .001), mHPA(C) -.42 (p less than .05) and PAA (U) -.37 (p less than .10), controlling for time incarcerated. In the principal investigation (N = 103), PAA(C) (p less than .01), pHPA (U) (p less than .05) levels, and MAO activity to TRYP (p less than .05) were lower among violent offenders. Factor scores of biochemical activity produced even more significant results. However, when these results were cross validated with data from the pilot study, only minimal relationships were maintained.

Trace acid levels in the plasma and MAO activity in the platelets of violent offenders

The plasma concentrations of the unconjugated and conjugated so-called "trace acids," phenylacetic acid (PAA), m- and p-hydroxyphenylacetic acid (mHPA, pHPA), and platelet monoamine oxidase (MAO) activity were measured in 103 male prisoners detained in a psychiatric institution. Twenty-three had been convicted of violent crimes, 18 of sexual offenses, 24 of armed robbery, 27 of nonviolent property offenses, and 11 of miscellaneous nonviolent offenses. Unconjugated pHPA and conjugated PAA were found to be significantly reduced in the violent offenders when compared with those of the "nonviolent" groups. The levels of pHPA were also found to be low in sexual offenders. Platelet MAO activities to phenylethylamine, tryptamine, and p-tyramine between any of the categories of prisoners were not significantly different.

Platelet monoamine oxidase activity and plasma levels of non-catecholic phenylethylamines in insulin-dependent diabetic subjects

The activity of blood platelets monoamine oxidase (MAO) was significantly reduced in a group of insulin-dependent diabetics when compared to sex- and age-matched controls. This enzymatic change was accompanied by a dramatic increase in the plasma levels of phenylethylamine, whereas no significant changes were observed for the concentration of either p-tyramine or phenylethanolamine. Levels of the o- and m-isomers of tyramine were below detectable limits (less than 0.050 ng/ml). A possible role of the MAO/monoamine system in the pathophysiology of diabetes is discussed.

Functional distinction between serotonin uptake and serotonin-induced shape change receptors in rat platelets

Tyramine and dopamine are taken up by rat platelets through the serotonin uptake mechanism while phenethylamine is not taken up. This indicates that an aromatic hydroxyl group is a structural requirement for the uptake of phenethylamine derivatives by rat platelets. Although none of these phenethylamine derivatives induce platelet shape change, they inhibit serotonin-induced shape change and serotonin uptake with the same relative potency (tyramine greater than phenethylamine greater than or equal to dopamine). This suggests that the receptors controlling serotonin uptake and serotonin-induced shape change have a common structural component that binds phenethylamine derivatives. However, the fact that phenethylamine derivatives activate the serotonin uptake mechanism but do not induce platelet shape change suggests that serotonin uptake and serotonin-induced shape change are mediated by two distinct activation sites of serotonin receptors.

Alterations in trace amine and trace acid concentrations in isolated aggressive mice

We have used an animal model of aggression, the isolation syndrome in mice, to examine the possible role of the trace amines, beta-phenylethylamine (PEA), meta-tyramine (m-TA) and para-tyramine (p-TA) in aggressive behaviour. The brain, plasma and urinary levels of PEA, m-TA and p-TA, and their respective major acid metabolites, phenylacetic acid (PAA), meta-hydroxyphenylacetic acid (m-HPA) and para-hydroxyphenylacetic acid (p-HPA) were measured in isolated aggressive mice (after fighting), and in group housed controls. The urinary levels of PEA, m-TA, PAA, m-HPA and p-HPA, and the plasma levels of PAA and p-HPA were significantly lower in isolated aggressive mice. Similarly, the whole brain levels of PEA, p-TA, PAA and p-HPA tended to be reduced. In contrast, the brain levels of m-TA and m-HPA tended to increase. It should be noted, however, that the present procedure did not dissociate the stress and aggression components of the isolation syndrome, and, therefore, further experiments are required to determine whether the observed neurochemical changes are functionally related to increased aggression.

Simultaneous radioenzymatic determination of phenylethylamine, phenylethanolamine, tyramine and octopamine in plasma of patients with hepatic encephalopathy

A sensitive radioenzymatic assay for the simultaneous determination of phenylethylamine, phenylethanolamine, tyramine and octopamine in plasma samples is reported. After extraction with ethanol, the amines are subjected to enzymatic N-methylation with labelled S-adenosylmethionine, preceded in the case of phenylethylamine and of tyramine, by an enzyme-catalyzed beta-hydroxylation step. The procedure is completed by extraction with toluene containing different amounts of isoamylalcohol, followed by controlled evaporation of the solvent. A generalized and highly significant increase in the concentration of all the four amines was found in plasma samples from patients suffering from hepatic encephalopathy.

Evidence for central hypertyraminemia in hepatic encephalopathy

In mongrel dogs, the effect of end-to-side portacaval shunt on plasma, cerebrospinal fluid (CSF) and brain tyramine, tyrosine, dopamine, norepinephrine, and epinephrine were studied. It was found that the level of tyramine in plasma, CSF, and selected brain regions increased steadily after the construction of the shunts. These elevations became more pronounced when the dogs manifested symptoms of hepatic encephalopathy. In postshunted dogs with stage II and III hepatic encephalopathy, tyramine concentration in corpus striatum (1,312 +/- 371), hypothalamus (400 +/- 67.0), and midbrain (660 +/- 78.7 ng/g) was significantly (P less than 0.05) higher than the level in dogs with stage 0 and I hepatic encephalopathy and sham-operated dogs serving as controls (corpus striatum, 831 +/- 140; hypothalamus, 167 +/- 40.0; and midbrain, 132 +/- 37.4 ng/g). This was followed by a concomitant depletion of dopamine and norepinephrine in these brain regions (postshunt: dopamine 104 +/- 20.0, 3,697 +/- 977, and 105 +/- 14.1; norepinephrine 521 +/- 71.6, 81.6 +/- 13.7, and 218 +/- 31.7 ng/g; vs. sham group: dopamine 532 +/- 83.1, 8,210 +/- 1,126, and 192 +/- 35.0; norepinephrine 1,338 +/- 425, 124 +/- 21.3, and 449 +/- 89.7 ng/g) of encephalopathic dogs with portacaval shunt. Furthermore, tyramine, tyrosine, dopamine, and norepinephrine levels in plasma and CSF increased markedly as clinical features in the dogs' behavior characteristic of hepatic encephalopathy occurred, including hypersalivation, ataxia, flapping tremor, somnolence, and coma. Cerebral hypertyraminemia and a defect in sympathetic neurotransmission may contribute to the development of hepatic encephalopathy of liver disease.