Some observations on the estimation of 3‐methoxytyramine in brain tissue

Guldberg, H. C.; Sharman, D. F.; P, Tegerdine

doi:10.1111/j.1476-5381.1971.tb07136.x

Cited by 26 publications

(3 citation statements)

References 13 publications

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“…Euler & Floding, 1955) or cysteine (e.g. Guldberg et al, 1971). However, in the present assay the redox potentials established by such combinations were unsuitable; in these cases the yellow ferricyanide colour disappeared almost instantaneously, in contrast to its slow disappearance when using sulphites.…”

Section: Theoretical Considerationsmentioning

confidence: 73%

“…Although 3-methoxytyramine is incompletely separated from dopamine in the present Dowex 50 procedure, its interference in the present assay (12-20%) is considerably less than after iodine oxidation (48%-personal observation of the method by Carlsson & Lindqvist, 1962). The overall interference by 3-methoxytyramine of less than 4% is acceptable for most purposes, since the ratio of dopamine to its major metabolite is normally high, and is rarely reversed 2A even after monoamine oxidase inhibition (Carlsson & Waldeck, 1964;Guldberg, Sharman & Tegerdine, 1971). Dopamine can be completely separated from noradrenaline and adrenaline on Dowex 50 columns (Bertler et al, 1958).…”

Section: Discussionmentioning

confidence: 84%

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The determination of dopamine by a modification of the dihydroxyindole fluorimetric assay

Atack

1973

British J Pharmacology

249

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Summary1. A simplified sensitive fluorimetric assay for dopamine based on the hydroxyindole principle is described. Oxidation of dopamine by ferricyanide and subsequent tautomerization both occur in the same, strongly alkaline, ethanolic solution in the presence of metabisulphite. The reaction is selfregulating, and since times of additions of reagents are relatively unimportant and the final fluorescence is very stable, a large number of samples can be assayed together.2. The method was developed for assaying dopamine in N-ethanolic (50%)-HCI eluates, after purification on a strongly acidic cation exchange column as previously described (Atack & Magnusson, 1970). Portions, up to 1 ml volume, of the 3 5 ml eluate can be taken. No preliminary, time-consuming, neutralization step is required before oxidation. Fluorescence intensity shows a linear re!ation with concentration for 1-5,000 ng of dopamine per 1-6 ml of final solution, both in pure solutions and in column eluates. 3. Fluorescence readings from biological material are given, with evidence for their reproducibility. These, together with other data, demonstrate the relative accuracy of the 'tissue blank' and indicate that amounts of dopamine greater than 3 ng per column can confidently be detected, and amounts greater than 10 ng can be measured quantitatively. 4. Fluorescence spectra are presented for the fluorophore derived from authentic dopamine, and from suspected dopamine extracted from spinal cord of normal rats and rats treated with reserpine plus an inhibitor of synthesis.Values for the concentration of dopamine of 20 and <3 ng/g, respectively, were obtained.

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Section: Theoretical Considerationsmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 84%

The determination of dopamine by a modification of the dihydroxyindole fluorimetric assay

Atack

1973

British J Pharmacology

249

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“…3-Methoxydopa was assayed in parallel 1 ml aliquots of the eluates by a method similar to that described for homovanillic acid by Anden et al (1963), for 3-methoxydopamine by Guldberg et al (1971) and for 3-methoxydopa by Fahn et al (1972). To a 1 ml sample eluate, 1 ml of concentrated (335/a) ammonia containing 20 ,ug potassium ferricyanide/ ml; two minutes later 0.1 ml of cysteine solution (1 mg/ml) was added.…”

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confidence: 99%

Plasma concentrations of L-dopa and 3-methoxydopa and improvement in clinical ratings and motor performance in patients with Parkinsonism treated with L-dopa alone or in combination with amantadine.

Pilling¹,

Baker²,

Iversen³

et al. 1975

Journal of Neurology, Neurosurgery & Psychiatry

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SYNOPSIS Six patients with idiopathic Parkinsonism were treated with a combination of amantadine and L-dopa and after 12 to 24 weeks amantadine was replaced by placebo for a six week period in a double-blind trial. Although there was a tendency for clinical disability ratings and scores on objective ratings of motor skills to deteriorate initially after amantadine removal, there was no significant deterioration in clinical improvement or motor performance during the period of amantadine withdrawal. Amantadine withdrawal also failed to cause any significant change in plasma concentrations of L-dopa or its metabolite 3-methoxy-dopa in these patients. In a group of 27 patients seen regularly as outpatients measurements of plasma L-dopa failed to correlate significantly with either oral dose or with clinical improvement scores. The plasma concentration of 3-methoxy-dopa, however, was on average 2.8 times higher than that of L-dopa, and there was a significant correlation between plasma levels of this metabolite and clinical improvement. It is suggested that 3-methoxy-dopa may contribute significantly to the therapeutic actions of L-dopa in Parkinsonism.Amantadine and L-dopa are in widespread use, either singly or in combination, in the treatment of patients with Parkinsonism. The combination of amantadine and L-dopa has been claimed to be more effective than L-dopa alone, although not all trials have confirmed this synergism (for review see Parkes et al., 1973). Amantadine has also been shown to decrease the daily L-dopa therapeutic dosage requirements and it has been suggested that amantadine may decrease the extracerebral metabolism of L-dopa, thus rendering more drug available to the central nervous system (Peaston et al., 1973). In the present study we present clinical and biochemical findings in a group of patients treated with the combination preliminary experiments showed that both compounds were stable under these storage conditions. Plasma samples (4 ml) were deproteinized by addition of 4 ml ice-cold O.4N perchloric acid, and stand-

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The Turnover of Catecholamines

Sharman¹

1981

Central Neurotransmitter Turnover

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Some observations on the estimation of 3‐methoxytyramine in brain tissue

Cited by 26 publications

References 13 publications

The determination of dopamine by a modification of the dihydroxyindole fluorimetric assay

The determination of dopamine by a modification of the dihydroxyindole fluorimetric assay

Plasma concentrations of L-dopa and 3-methoxydopa and improvement in clinical ratings and motor performance in patients with Parkinsonism treated with L-dopa alone or in combination with amantadine.

The Turnover of Catecholamines

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