MHPG Sulphate Research Articles

Comparison of influence of aerobic exercise, in water walking and yogic exercise, on 3-methoxy –4-hydroxy phenyl glycol-sulfate in depressed girls

Depression is a clinical disorder distinguished by physiological and psychological markers. Some studies have indicated that during depression some neural chemical transmitters including epinephrine are reduced. It seems that these chemical changes can cause depression symptoms. 3-metoxy-hydroxyphenyl glycol-sulphate (MHPG) is a metabolite of epinephrine that released from presynaptic nerve terminals of central nervous system and became sulphate in brain. It cross the blood-brain barrier and showed as a sulphate combination in urine. The propose of this proposal, was to determine the effect of 8 weeks of aerobic exercise, walking in water and yogic exercise on urine MHPG sulphate in the depressed girls.

Determination of 4-hydroxy-3-methoxyphenylethylene glycol 4-sulfate in human urine using liquid chromatography-tandem mass spectrometry.

A major metabolite of norepinephrine (NE) in brain is 4-hydroxy-3-methoxyphenylethylene glycol (MHPG). In many species, a large fraction of MHPG formed in brain is converted to the sulfate conjugate. Consequently, MHPG sulfate has been proposed as a biomarker for NE metabolism in the central nervous system. As part of the clinical trials of the monoamine oxidase inhibitor selegiline for treating cocaine addiction, we required a method for measuring urine concentrations of MHPG sulfate. Using a deuterium-labeled analogue as an internal standard, we developed a liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/ MS) method for determination of MHPG sulfate in human urine. Sample preparation involves simply diluting 50 microL of urine with 1 mL of ammonium formate buffer and adding the internal standard. The sample is centrifuged, the supernate is transferred to an autosampler vial, and 10 microL is injected into the LC-MS/MS system. Standard curves from 50 to 10,000 ng/mL are generated. Only one sample of 277 clinical samples analyzed had a concentration outside of this range. Precision (coefficient of variation) ranged from 1.9 to 9.7%, and accuracy ranged from 97 to 103% of expected values for controls prepared by spiking sulfatase-treated urine with MHPG sulfate.

Endocrine and neurochemical effects of (+)-PHNO, a dopamine D2 agonist

The naphthoxazine compound, (+)-PHNO, is a dopamine D2 receptor agonist which acts within the central nervous system. The effects of this drug on serum concentrations of corticosterone and prolactin and on brain concentrations of catecholamines and some of their metabolites were determined in male rats. Administration of (+)-PHNO in doses ranging from 3-300 micrograms/kg i.p. resulted in increased serum corticosterone, decreased serum prolactin and decreased concentrations of the dopamine metabolites, DOPAC and HVA, in the brain. At the higher doses of (+)-PHNO, concentrations of MHPG sulfate in the brain stem were increased and hypothalamic epinephrine concentrations were decreased. Pretreatment with centrally acting dopamine antagonists (spiperone or haloperidol) prevented the (+)-PHNO-induced changes in serum corticosterone, prolactin and brain catecholamines. In contrast, pretreatment with halopemide, a dopamine antagonist which penetrates poorly into the brain, was unable to block the effects of (+)-PHNO on serum corticosterone and brain catecholamines. These data show that (+)-PHNO, a dopamine agonist structurally unrelated to other dopamine agonists, acts centrally to affect serum corticosterone and brain catecholamines.

Relationships between catecholamine or 3-methoxy 4-hydroxy phenylglycol changes and the mental performance under submaximal exercise in man.

Eleven young students were tested to determine the relationship between the improvement of mental performances observed under prolonged submaximal work and central or peripheral catecholamine changes. The subjects pedaled a bicycle ergometer for 1 h at a work load individually calculated to approximate 75% of maximal oxygen uptake. The mental test, consisting of 1-h sessions of time-limited word tests and arithmetical calculations, required a high degree of concentration (vigilance and short-term memory). Catecholamines [epinephrine (E), norepinephrine (NE), dopamine (DA)], metanephrine (MN), normetanephrine (NMN) and the glucuronide conjugate of 3-methoxy 4-hydroxyphenylglycol (MHPG) were assayed in urine to assess peripheral activity: E and MN as indexes of adrenomedullary secretion, NE, NMN and MHPG glucuronide as markers of NE metabolism in sympathetic nerves. Urinary MHPG sulfate was determined as a possible marker of central noradrenergic metabolism. When compared to the effect of single tests, the combination of prolonged submaximal work and mental task induced significant increases in MHPG sulfate and E + MN excretions. Both these increases were correlated each to one another and also correlated to the number of discriminated words. Altogether, the present data show that prolonged submaximal work under mental load activates catecholamine systems and suggest that a relationship exists between adrenomedullary activation and the improvement of mental performance. Based on literature data, the possible modulatory role of peripheral E on mental processes and central noradrenergic activity is discussed.

Decrease in hypothalamic epinephrine concentration and other neurochemical changes produced by quinpirole, a dopamine agonist, in rats.

Quinpirole, (4 aR-trans)-4, 4a, 5, 6, 7, 8, 8a, 9-octahydro-5-propyl-1 H-pyrazolo [3, 4-g]quinoline, is a dopamine agonist selective for the D2 subtype of dopamine receptors. In rats, quinpirole at doses of 0.3 mg/kg i.p. and higher decreased hypothalamic epinephrine concentrations. The doses required for this effect are only slightly higher than the minimum doses that decreased the concentration of dopamine metabolites in cerebral hemispheres. At higher doses of quinpirole (2-3 mg/kg i.p.), dopamine concentration was increased and norepinephrine concentration was decreased in hypothalamus, and MHPG sulfate (the norepinephrine metabolite) concentration was increased in brain stem and in hypothalamus. All of these neurochemical effects of quinpirole were blocked by pretreatment with spiperone, a dopamine antagonist. The effects were not produced by SKF 38393, a selective D1 agonist, or by the dextrorotatory enantiomer of quinpirole, which lacks D2 agonist activity. The data support the interpretation that quinpirole, by activating D2 receptors, results in a decrease in dopamine metabolites, a decrease in hypothalamic epinephrine concentration, and an increased conversion of norepinephrine to MHPG sulfate in rat brain probably through enhanced norepinephrine release.

Pergolide elevation of MHPG sulphate concentration in rat hypothalamus blocked by spiperone and mimicked by other dopamine agonists

Pergolide increased the concentration of MHPG sulphate (3-methoxy-4-hydroxy-phenylethylene glycol sulphate) in rat hypothalamus, and the increase was prevented by pretreatment with spiperone, a dopamine antagonist. An increase in hypothalamic MHPG sulphate concentration similar to that caused by pergolide was found after injection of quinpirole, a 'partial ergoline' that is a selective D2 agonist not affecting alpha-adrenoceptors, and by (-)-N-propylnorapomorphine, a dopamine agonist not related to the ergolines. Although the increase in MHPG sulphate concentration produced by pergolide had earlier been assumed to result from blockage of alpha-adrenoceptors, the present data indicate that it is an effect produced by dopamine D2 receptor stimulation.

3-Methoxy-4-hydroxyphenylglycol in human cerebrospinal fluid

3-Methoxy-4-hydroxyphenylglycol (MHPG) free and sulphate conjugate concentrations were investigated in human lumbar cerebrospinal fluid from a group of 48 subjects of both sexes, using a sensitive and direct reversed-phase liquid chromatographic method with amperometric detection, improved with the adoption of 4-methoxy-3-hydroxyphenylglycol (iso-MHPG) as internal standard. The mean value of free MHPG was 7.30 ± 1.90 μg/1 (SD) and 8.10 ± 2.8 μl/1 in males (28) and females (20) respectively, and the MHPG sulphate conjugate represented about 5% of free metabolite in both sexes. In addition, the correlations between MHPG levels and patients' age and sex were also discussed, as were criteria for subject selection.

Human platelet phenol sulphotransferase: Assay procedure, substrate and tissue correlations

Procedures for the precise assay of human platelet phenol sulphotransferase activity were determined. The coefficient of variation of the assay was 5.8% when the enzyme activity was expressed per 10 8 platelets, and was 9.4% when it was expressed per mg soluble platelet protein. Mean platelet phenol sulphotransferase (PST) activity in samples from 102 randomly selected adults was 1.2 ± 0.4 units/10 8 platelets (mean ± S.D.), with a range from 0.2 to 2.9. The mean activity for umbilical cord blood platelet PST was 0.93 ± 0.3 units/10 8 platelets (mean ± S.D., n = 27). The substrate used routinely for the assay was 3-methoxy-4-hydroxyphenylglycol (MHPG). There was a significant correlation between the formation of MHPG sulfate by individual platelet preparations and the formation of sulfated product with each of the following substrates: tyramine ( r = 0.92, n = 21); dopamine ( r = 0.82, n = 16); 5-hydroxytryptamine ( r = 0.94, n = 20); acetaminophen ( r = 0.77, n = 17); and alphamethyldopa ( r = 0.77, n = 17) ( p < 0.001 for each). Platelet PST activity correlated significantly with human renal cortex PST activity ( r = 0.54, n = 20, p < 0.02). The correlation coefficient between platelet PST activity and jejunal mucosal enzyme activity in eight patients was 0.67. These results raise the possibility that human platelet PST activity measured with MHPG as substrate might reflect the enzyme activity in other tissues and the degree of sulfate conjugation of a variety of substrates.

Stereoselective excretion of (3-methoxy-4-sulphooxyphenyl)ethylene glycol (MHPG sulphate) in the dog.

3-Methoxy-4-hydroxyphenylethylene glycol (MHPG) labelled with six deuterium atoms ([2H6]MHPG) was infused into two female greyhound dogs. Plasma and urine were analyzed for endogenous MHPG and [2H6]MHPG and their conjugates by the technique of selected ion monitoring gas chromatography-mass spectrometry. This analysis showed that the major forms of MHPG and [2H6]MHPG in the plasma and urine of the greyhounds were the sulphate conjugates. However, the plasma concentration of [2H6]MHPG sulphate increased continuously during the infusion period and the renal clearance of this compound was found to be much less than that of the endogenous sulphate. The explanation that his was due either to saturation of a renal transport mechanism or to a deuterium isotope effect was eliminated. Stereochemical analysis showed that, while the [2H6]MHPG used for infusion was a racemic mixture of two stereoisomers, much more of the nature(-)stereoisomer of [2H6]MHPG sulphate was excreted in the dog urine. It was also shown that both the (+) and (-)stereoisomers of [2H6]MHPG sulphate were sulphoconjugated at the 4-position of the aromatic ring.

Phenolsulphotransferase in human tissue: Radiochemical enzymatic assay and biochemical properties

Phenolsulphotransferase (EC 2.8.2.1) (PST) is an important catecholamine and drug metabolizing enzyme. Optimal conditions have been determined for the accurate measurement of PST activity in the human platelet, human renal cortex, and human jejunum with a radiochemical microassay. 3-Methoxy-4-hydroxyphenylglycol (MHPG) and 35 S−3'-phosphoadenosine-5'-phosphosulfate ( 35 S-PAPS) were the substrates for the reaction. The apparent Michaelis-Menten ( K m ) values for MHPG with platelet, renal cortex, and jejunum were 1.09, 0.46 and 1.16 mmol/l, respectively. Apparent K m values for PAPS in the same tissues were 0.14, 0.13 and 0.21 μmol/l. The pH optimum of the reaction in all three tissues was approximately 6.2-6.8 with three different buffer systems. The coefficients of variation for the assay of platelet, renal cortex, and jejunal activities were 6.2%, 3.4% and 4.4%, respectively. Mean platelet PST activity in blood samples from 75 randomly selected adult subjects was 5.0 ± 1.72 nmol of MHPG sulfate formed per hour per mg of platelet protein (8.3 × 10 −5 ± 2.9 × 10 −5μmol · min −1 · mg −1, mean ± S.D.). There was a 5-fold intersubject variation in platelet PST activity within two standard deviations of the mean value. Experiments in which partially purified human erythrocyte PST was added to platelet, kidney and gut homogenates under these assay conditions provided evidence that endogenous PST inhibitors did not affect the observed enzyme activity.

A non-enzymic procedure for the quantitative analysis of (3-methoxy-4-sulphoxyphenyl)ethylene glycol (MHPG sulphate) in human urine using stable isotope dilution and gas chromatography—mass spectrometry

A method is described for the quantitative analysis of (3-methoxy-4-sulphoxyphenyl)-ethylene glycol (MHPG sulphate) in human urine, based on selected ion monitoring gas chromatography--mass spectrometry and using a specifically deuterium-labelled analogue of MHPG sulphate as internal standard. The procedure involves extraction of the urine sample on Amberlite XAD-2, followed by isolation of MHPG sulphate by column chromatography on Sephadex LH-20. Cleavage of the sulphate conjugate and formation of the MHPG tris(trifluoroacetate) derivative are carried out in a one-step reaction, without recourse to enzymic hydrolysis.

Metabolism of of catecholamines—Identification and quantification of 3-methoxy-4-hydroxyphenylglycol glucuronide in human urine

The glucuronic acid conjugate of 3-methoxy-4-hydroxyphenylglycol(MHPG) has been isolated from human urine and its identification is described. This compound has been found to be a metabolite of dl-MHPG- 3h and of DL-norepinephrine- 14C. The quantities of MHPG, MHPG sulfate and MHPG glucuronide which are present in normal human urine, and in the urine of patients with neuroblastoma, ganglioneuroma and pheochromocytoma, indicate that the glucuronic acid conjugate is a major metabolite of MHPG. In addition, MHPG and its conjugates are markedly increased in the urine of most patients with tumours of neural crest origin. This finding provides further evidence that MHPG is the major metabolite formed within these tumours, and the assay of urinary MHPG, especially after enzymatic hydrolysis of the glucuronide and sulfate conjugates, should be of value in the diagnosis of tumors of neural crest origin.