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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 45 (1985), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: An increase of free 3,4-dihydroxyphenylethylamine (DA, dopamine) in the rat brain such as is found following 3,4-dihydroxyphenylalanine (L-DOPA) administration or an intraventricular injection of free dopamine did not result in DA sulfate formation, despite the presence of phenolsulfotransferase activity in various regions of the brain and the high affinity of DA for this enzyme. However, when rats were pretreated with pargyline, a monoamine oxidase inhibitor, the same treatment with L-DOPA or free DA led to active synthesis of DA sulfate. The increase in DA sulfate was significantly correlated with the degree of monoamine oxidase inhibition and directly proportional to free DA concentrations in the hypothalamus (r = 0.86), striatum (r = 0.54), and brain-stem (r = 0.89). The highest ratio of DA sulfate to free DA was found in the hypothalamus, suggesting that sulfoconjugation is most active in this region. Prior treatment of rats with 6-hydroxydopamine did not decrease DA sulfate concentrations, indicating that sulfoconjugation occurs most likely in extraneuronal tissues not destroyed by the neurotoxin. The results are compatible with the notion that phenolsulfotransferase may be highly compartmentalized and that inhibition of monoamine oxidase allows the newly generated free DA to become accessible to the sulfoconjugating enzyme, resulting in increase in DA sulfation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of subeutaneous injection of l-β-3,4-dihydroxyphenylalanine (l-DOPA) on the concentrations of the catecholamines and catecholamine sulfates in the central and peripheral nervous Systems of the rat were studied. The results showed that free 3,4-dihydroxyphenylethylamine (DA, dopamine) increased rapidly and markedly in the hypothalamus and striatum after l-DOPA but DA sulfate did not change. Increased concentrations of DA sulfate were detected in the CSF and in the plasma, where it reached a concentration of 130.8 ± 12.8 ng/ml at 2 h, seven times the level of free DA (19.1 ± 2.9 ng/ml). In the kidney the ratio of DA sulfate to free DA was reversed in favor of free DA. Urine samples of l-DOPA-treated rats showed a higher increase of free DA than DA sulfate, but free norepinephrine (NE) and NE sulfate remained unchanged. Concentrations of free DA and free NE in the adrenal glands of l-DOPA-treated rats showed no change. Adrenal DA sulfate and NE sulfate were not detectable in the control and l-DOPA-treated rats, suggesting that the adrenal glands lack the capacity to take up or store catecholamines and their sulfate counterparts from the plasma.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In the present study, we found that large quantities of dopamine (DA) glucuronide were present in rat cerebrospinal fluid (CSF), plasma, and urine, whereas the glucuronides of norepinephrine (NE) and epinephrine (E) were almost undetectable. The high urinary excretion of DA glucuronide was in a range comparable to that of homovanillic acid (HVA). Sulfates of DA, NE, and E were measurable in all three body fluids, but only in small quantities. The measured DA glucuronide was predominantly of endogenous origin, as the feeding of sucrose instead of routine diet did not reduce the urinary output of DA glucuronide. Adrenalectomy but not peripheral sympathectomy induced by chronic guanethidine injection substantially decreased plasma DA glucuronide concentrations, indicating that the adrenals serve as an important source of endogenous DA glucuronide. The data suggest that glucuronidation constitutes an important metabolic pathway for endogenous DA of central and peripheral origin in rats; this route, however, is exclusive to DA and appears to play a negligible role for NE and E.
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  • 4
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We determined free and sulfoconjugated catecholamines (CA) in adrenals of several species by reverse-phase high performance liquid chromatography (HPLC) with electrochemical detection. The two main adrenal CA, free epinephrine (E) and norepinephrine (NE) from eight species (guinea-pig, rat, dog, mice, bovine, cat, green-monkey and human) were considerably different both in the total amount as well as their relative proportions. Free dopamine (DA) content also differed from species to species but this CA was present in a relatively constant proportion, representing about 1% of the total free CA. Phenolsulfotransferase (PST) activity was present in all of the adrenals. Sulfoconjugated CA, however, were only selectively present: E and NE sulfate were entirely absent but in most of these species DA sulfate was detected in a proportion corresponding to 1–10% of the total (free + sulfoconjugated) DA. The adrenal DA sulfate concentrations did not parallel the adrenal PST activity, indicating that this enzyme can not be considered to be an index of the CA sulfates present in this organ.
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 32 (1967), S. 1230-1231 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 61 (1993), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes, via its metabolite 1-methyl-4-phenylpyridinium (MPP+), parkinsonism in humans, monkeys, and mice but not in rats. When incubated with mouse brain homogenates, [3H]-MPP+ is recovered in relatively large concentrations in the brain cell nucleus. Although isolated cell nuclei from rat and mouse brain contain uptake systems for dopamine (DA), only brain cell nuclei from mice avidly take up [3H]MPP+. This nuclear uptake is ATP dependent and can be blocked by ouabain and Nethylmaleimide. It is not, however, affected by neuronal and vesicular blockers such as benztropine. mazindol, and reserpine. Selective uptake of MPP+ into brain cell nuclei may provide a new avenue for future investigation into the complex modes of action of the neurotoxin MPTP.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This study analyzed dopamine (DA) and norepinephrine (NE) in the synaptic vesicles and cytoplasm of brains of rats of 2 months and 14 months. The data revealed a clear NE increase in the synaptic vesicles of the 14-month-old rats, contrasting with NE in the cytoplasmic fraction of the rat brain, which remained unchanged with age. Synaptic vesicles from different regions of rat brain, including those from the striatum, consistently exhibited higher NE than DA concentrations, suggesting that they are predominantly noradrenergic. In the brain, DA concentrations in vesicular and cytoplasmic fractions did not vary with age, whereas in the superior cervical ganglia DA and NE concentrations increased in the older rats. L-3,4-Dihydroxyphenylalanine administration significantly increased DA without affecting NE in the ganglia of rats of all ages. In the brain, such a treatment significantly raised DA only in the synaptic vesicles of the older rats, suggesting an increased facilitation of DA transport into the synaptic vesicles with age, which may account for the higher vesicular NE in the older rats.
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The relationship between phenolsulfotransferase (PST) and catechol-O-methyltransferase (COMT) in the metabolism of free 3,4-dihydroxyphenylethylamine (DA, dopamine) in the rat brain was studied. In rats not pretreated with a monoamine oxidase (MAO) inhibitor a huge increase of free DA in the brain, following an intraperitoneal injection of L-3,4-dihydroxyphenylalanine (L-DOPA) or an intraventricular injection of free DA, did not lead to any noticeable change in DA sulfate or 3-methoxytyramine (3-MT), which remained undetectable by the present HPLC method. However, in rats previously treated with the MAO inhibitors pargyline or tranylcypromine, the same L-DOPA or free DA treatment resulted in significant increases in both 3-MT and DA sulfate in the hypothalamus, brainstem, and striatum. This response of COMT and PST was not affected by prior treatment of the rats with 6-hydroxydopamine, which suggests that O-methylation and sulfoconjugation occur outside adrenergic neurons not destroyed by the neurotoxin. Inhibition of COMT activity did not lead to any increase in DA sulfate, which showed that despite their common mode of action (both enzymes react preferentially at the same hydroxyl group in the DA molecule), the two enzymes are not competitive. After MAO inhibition there were strong correlations between an increase in DA sulfate and 3-MT on the one hand, and between free DA and 3-MT on the other. Because 3-MT is a marker of central DA release, these data suggest that inhibition of MAO activity not only affects DA metabolism by this enzyme but also influences DA release in the rat brain.
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