Effect of acute administration of large neutral and other amino acids on urinary excretion of catecholamines

Agharanya, Julius C.; Wurtman, Richard J.

doi:10.1016/0024-3205(82)90607-5

Cited by 25 publications

(19 citation statements)

References 10 publications

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“…This finding is consis tent with that observed following acute intra peritoneal administration of Tyr [2,3]. Carbidopa, a peripheral decarboxylase inhibitor, was used by these investigators to demon strate that the Tyr-induced enhancement of urinary catecholamine excretion was me diated peripherally.…”

Section: Discussionsupporting

confidence: 62%

“…Tyr is a sub strate whose hydroxylation is the rate-limit ing step in catecholamine synthesis [8], al though Tyr hydroxylase is not saturated with substrate under normal conditions [4], Hence, the synthesis of catecholamines can be enhanced by increasing the availability of Tyr in the brain (20,37], Several studies have now demonstrated that under certain experi mental conditions, CNS production and me tabolism of catecholamines follow the avail ability of Tyr [20,37,39], Furthermore, in creased urinary excretion of catecholamines has been demonstrated following an acute intraperitoneal administration of Tyr [2,3]. While it is difficult to argue against a modu lation of catecholamine metabolism by Tyr under acute experimental conditions using large doses of highly soluble Tyr conjugates, the physiologic relevance of this finding has been questioned [9,36].…”

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confidence: 99%

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Physiologic Responses to Chronic Dietary Tyrosine Supplementation in DOCA-Salt-Treated Rats

et al. 1986

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The antihypertensive effect of chronic administration of L-tyrosine (Tyr) was investigated in a two-part study. In the first experiment, adult male Sprague-Dawley rats were assigned to 1 of 4 treatment groups: (1) control diet plus unilateral nephrectomy (Nphx) and 0.15 M NaCl (Sal) as the sole drinking solution (C-CTRL); (2) control diet plus deoxycorticosterone acetate (DOCA, 268 μg/rat/day), Nphx, and Sal (C-DOCA); (3) control diet supplemented with 2.5% L-p-Tyr plus Nphx and Sal (Tyr-CTRL), and (4) Tyr plus DOCA, Nphx, and Sal (Tyr-DOCA). Systolic blood pressure (SBP) increased within 2 weeks after initiation of treatment with DOCA-salt and remained elevated throughout the duration (8 weeks) of the study (p < 0.001). Dietary administration of Tyr to DOCA-treated rats failed either to affect SBP in normotensive rats or the elevation of SBP in DOCA-treated rats. Dietary supplementation with Tyr induced a significant elevation in urinary excretion of free dopamine (week 1, 3, 5, and 7) and a decreased excretion of free norepinephrine (week 1) without regard to DOCA treatment. Metabolic reponsiveness (change in colonic temperature) and cardiovascular responsiveness (change in heart rate) to subcutaneous administration of the β-adrenergic agonist, isoproterenol, were significantly prolonged while α₂-adrenoceptor number (cerebral cortical membranes; ³H-yohimbine binding) was reduced in rats receiving Tyr. In the second experiment, similar rats were assigned to 1 of 3 treatment groups: (1) control diet plus Nphx and Sal, (2) control diet plus Nphx, DOCA and Sal, and (3) Tyr plus DOCA, Nphx, and Sal; however, Tyr was not started until DOCA-salt-induced hypertension developed (4 weeks). Neither acute (2.5 h post-meal) nor chronic (4 weeks) effects of administration of Tyr on SBP were noted. Thus, the Tyr-induced changes observed in these studies include a chronic increase in free dopamine, and a transient decrease in norepinephrine, excretion. No significant effects of Tyr on blood pressure of DOCA-salt-treated rats were observed.

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Section: Discussionsupporting

confidence: 62%

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confidence: 99%

Physiologic Responses to Chronic Dietary Tyrosine Supplementation in DOCA-Salt-Treated Rats

et al. 1986

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“…In the rat, manipulations of plasma amino acid concentrations have demonstrated that brain tyrosine concentrations are directly related to the ratio of the plasma concentration of tyrosine to the sum of the concentrations of the other LNAA (Fernstrom & Faller, 1978;Agharanya & Wurtman, 1982). On the basis of the evidence in experimental animals, the increment in this ratio in our study can be expected to have increased the uptake of tyrosine across the blood brain barrier and into the neurones.…”

Section: Dicussionsupporting

confidence: 54%

Modulation of the actions of tyrosine by α₂‐adrenoceptor blockade

Al-Damluji

Ross

Touzel

et al. 1988

British J Pharmacology

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1 Eight normal subjects were given, in double-blind, random order L-tyrosine 50, 250 and 500mg kg-1 and placebo orally. Plasma tyrosine concentrations rose in a dose-dependent manner, without affecting the concentrations of the other large neutral amino acids. Tyrosine stimulated the secretion of prolactin and thyrotrophin (TSH) but had no effect on the plasma concentrations of adrenocorticotrophic hormone (ACTH), cortisol, growth hormone or the gonadotrophins. 2 The lack of a stimulant effect of tyrosine on ACTH secretion was presumed to be due to activation of one of the negative feedback mechanisms that control the rate of synthesis and release of the catecholamines, and this hypothesis was tested by examining the effects of the a2-adrenoceptor antagonist idazoxan on the actions of tyrosine. 3 Seven normal males were given on 6 separate occasions tyrosine 250 and 500mg kg~and placebo orally following pretreatment with saline and idazoxan (O.1mgkg-1 i.v.). Following pretreatment with idazoxan, tyrosine stimulated the secretion of ACTH and noradrenaline in a dose-dependent manner, although neither tyrosine nor idazoxan on their own had any effect on the secretion of either substance. 4 The lack of effect of tyrosine when given on its own appears to be due, partly, to activation of a2-adrenoceptors, which inhibit the release of noradrenaline. Idazoxan caused a small increase in systolic blood pressure, both when given on its own and in combination with tyrosine. Neither tyrosine nor idazoxan had any significant effect on the state of behavioural arousal, as measured by visual analogue scales, or on the secretion of growth hormone or the gonadotrophins.

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“…Increasing the plasma tyrosine ratio can accelerate catecholamine synthesis and release Carlsson and Lindqvist, 1978) thereby exerting physiologic effects such as increasing blood pressure during hemorrhagic shock (Conlay et al, 1981) and decreasing blood pressure in spontaneously hypertensive rats (Sved et aI., 1979). Agharanya et al (1982) demonstrated that a 76% rise in plasma tyrosine was associated with an 82% rise in the tyrosine LNAA ratio, a 55% rise in the brain tyrosine concentration, and a doubling in urinary catecholamine excretion. In contrast, Schweiger et al (1985) demonstrated that a decrease in the tyrosine/LNAA ratio of 63% decreased brain tyrosine by 27%, and was associated with a 30% decrease in brain norepinephrine release.…”

Section: Discussionmentioning

confidence: 97%

Effects of running the Boston marathon on plasma concentrations of large neutral amino acids

Conlay

Wurtman

G-Coviella

et al. 1989

J. Neural Transmission

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Plasma large neutral amino acid concentrations were measured in thirty-seven subjects before and after completing the Boston Marathon. Concentrations of tyrosine, phenylalanine, and methionine increased, as did their "plasma ratios" (i.e., the ratio of each amino acid's concentration to the summed plasma concentrations of the other large neutral amino acids which compete with it for brain uptake). No changes were noted in the plasma concentrations of tryptophan, leucine, isoleucine, nor valine; however, the "plasma ratios" of acid patterns may influence neurotransmitter synthesis.

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Effect of acute administration of large neutral and other amino acids on urinary excretion of catecholamines

Cited by 25 publications

References 10 publications

Physiologic Responses to Chronic Dietary Tyrosine Supplementation in DOCA-Salt-Treated Rats

Physiologic Responses to Chronic Dietary Tyrosine Supplementation in DOCA-Salt-Treated Rats

Modulation of the actions of tyrosine by α₂‐adrenoceptor blockade

Effects of running the Boston marathon on plasma concentrations of large neutral amino acids

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Effect of acute administration of large neutral and other amino acids on urinary excretion of catecholamines

Cited by 25 publications

References 10 publications

Physiologic Responses to Chronic Dietary Tyrosine Supplementation in DOCA-Salt-Treated Rats

Physiologic Responses to Chronic Dietary Tyrosine Supplementation in DOCA-Salt-Treated Rats

Modulation of the actions of tyrosine by α2‐adrenoceptor blockade

Effects of running the Boston marathon on plasma concentrations of large neutral amino acids

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Modulation of the actions of tyrosine by α₂‐adrenoceptor blockade