The rate of incorporation of amino acids into brain proteins during infusion in the rat

Seta, Kiichiro; Sansur, M.; Lajtha, Ábel

doi:10.1016/0005-2787(73)90103-2

Cited by 59 publications

(18 citation statements)

References 23 publications

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“…According to Seta, Sansur, and Lajtha (1973) the "half-life" of brain proteins is some 4-14 days. If we take a value of 7 days this means a requirement for the rabbit of about 3 g of protein in 7 days or about 0.4 glday.…”

Section: Utilization Of Amino Acidsmentioning

confidence: 99%

Ventriculo–cisternal perfusion of twelve amino acids in the rabbit

et al. 1982

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The clearances of twelve amino acids from the ventricles during ventriculo-cisternal perfusion in the rabbit have been measured; uptake by the brain was also measured and this permitted the separate computation of loss to brain and loss to blood during the perfusion. Clearance under carrier-free conditions was greater than when a concentration of 5mM unlabeled amino acid was present in the perfusion fluid. Brain uptake was also usually reduced by the presence of unlabeled amino acid due presumably to suppression of accumulation by brain cells. Reduction of transport across the blood-brain barrier would tend to increase brain uptake, and there was some evidence for a balance between the two opposing tendencies. Inhibition of clearance of a given labeled amino acid could be brought about by unlabeled amino acids of different molecular species. In general, the amino acids fell into three categories: neutral, acidic, and basic, and there was some overlap between them; of the neutral amino acids the A- and L-classification of Christensen was valid, although once again there was some overlap. If, during ventriculo-cisternal perfusion of a labeled amino acid, the activity of this labeled amino acid in the blood was raised well above that in the inflowing perfusion fluid, the labeled amino acid continued to be cleared from the perfusion fluid, suggesting uphill transport. On this basis it was suggested that the normally low concentrations of amino acids in the cerebrospinal fluid (CSF), by comparison with those in plasma, were due to an active transport from the CSF to the blood. Substrate-facilitated transport, whereby the penetration of labeled amino acid into the perfusion fluid from blood could be accelerated by adding unlabeled amino acid to the perfusion fluid, or vice versa, was demonstrated.

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Section: Utilization Of Amino Acidsmentioning

confidence: 99%

Ventriculo–cisternal perfusion of twelve amino acids in the rabbit

et al. 1982

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“…The 3-fold increase in brain contents of homocarnosine in the malnourished monkeys in comparison to the control animals is difficult to explain, and probably reflects either increased synthesis as a result of increased substrate availability and elevated activity of carnosine synthetase [L-histidine: 8-alanine ligase (AMP); EC 6.3.2.1 I] or decreased metabolism resulting from reduced activity of the catabolic enzyme, carnosinase (aminoacyl-L-histidine hydrolase : EC 3.4.3.3). The brain is metabolically active and exhibits rapid renewal of proteins in spite of very little cell turnover (SETA et al, 1973). The findings reported here assume special significance in the light of reports of several human cases (See SANO, 1970;STIFEL and HERMAN, 1971, for reviews) in whom severe neurological disorders were associated with high levels of homocarnosine in the CSF (PERRY et al, 1967), blood (PERRY et al, 1967, brain (SCRIVER et al, 1966) and urine (BESSMAN and BALDWIN, 1962;LEVENSON et al, 1964;PERRY et al, 1967).…”

Section: Resultsmentioning

confidence: 99%

ACCUMULATION OF HISTIDINE, 3‐METHYLHISTIDINE, AND HOMOCARNOSINE IN THE BRAINS OF PROTEIN‐CALORIE DEFICIENT MONKEYS¹

Enwonwu

Worthington

1973

Journal of Neurochemistry

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Abstract— Seventeen monkeys (M. nemestrina and M. fascicularis) aged 10 months to about 5 yr were divided into two groups and fed either an adequate protein diet (20% casein) or a low‐protein diet (2% casein). The diets were supplied to the animals in restricted amount (200 g/animal in two daily rations). In one experiment, the malnourished animals were initially fed a diet containiing 8 per cent protein and the protein content of the diet was gradually reduced over a period of 9 months, to 2 per cent. After about 3 months on the 2 per cent protein diet, the malnourished monkeys showed growth failure, severe anorexia, peri‐ocular oedema, tremors of the head and limbs, atrophy of several visceral organs, fatty liver, hypoalbuminaemia, and depressed serum levels of many essential amino acids with an elevation of the ratio of non‐essential to essential amino acids. These features are consistent with protein‐calorie malnutrition. Examination of the brains revealed significant alterations in the levels of glycerophosphoethanolamine (—40 per cent), glutamic acid (—25 per cent), histidine (+230 per cent), homocamosine (+185 per cent), 3‐methyl‐histidine (+147 per cent), lysine (+55 per cent), phenylalanine (+33 per cent) and tyrosine (+26 per cent) in comparison to findings on the well‐fed monkeys. The possible implications of elevated cerebral contents of homocarnosine in malnourished monkeys are discussed in the light of several reported human cases in whom neurological disorders are associated with increased histidine‐containing dipeptides in the brain, CSF, blood and urine.

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“…For example, Shahbazian et ai. (1987), using e4C]valine, reported the cerebral protein synthesis rate to be 0.6%/h, while Seta et al (1973) have found that the turnover per hour varied from 0.3 to 0.7% depending on the amino acid considered, with half-lives ranging between 4.5 and 9 days.…”

Section: Discussionmentioning

confidence: 99%

Regional Cerebral l-[¹⁴C-Methyl]Methionine Incorporation into Proteins: Evidence for Methionine Recycling in the Rat Brain

Planas

Prenant

Mazoyer

et al. 1992

J Cereb Blood Flow Metab

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Summary:The specific activity (SA) of free methionine was measured in plasma and in different regions of the rat brain at 15, 30, or 60 min after intravenous infusion of L-[I4C-methyl]methionine. Within these time periods, an apparent steady state of labeled free methionine in plasma and in brain was reached. However, the brain-to-plasma free methionine SA ratio was found to be �0.5, showing that an isotopic equilibrium between brain and plasma was not attained. This suggests the presence of an endog enous source of brain free methionine (likely originating from protein breakdown), in addition to the plasma Attempts to measure the regional rate of protein synthesis in the brain with positron emission tomog raphy (PET) have been made using several llC _ labeled amino acids, principally L-[llC-methyl] methionine (Bustany et ai., 1983(Bustany et ai., , 1985 Ericson et ai., 1987) and L-[1 _ 11C]leucine (Phelps et ai., 1984; Hawkins et ai., 1989). L-[llC-Methyl]Methionine is currently employed in PET for the evaluation of local amino acid uptake in various physiological and pathologic conditions of the human brain (Comar et ai., 1981; Bergstrom et ai., 1987a,b; Mosskin et ai., 1987; Hatazawa et ai., 1989; Mineura et ai., 1991; O'Tuama et aI., 1991). Yet for neither methionine nor leucine has a satisfactory model been so far developed that would allow the estimation of local rates of cerebral protein synthesis (Smith et ai., 1988; Hargreaves-Wall et aI., 1990). This is mostly due to the fact that amino acids derived from pro tein breakdown in the human brain might be recy cled for protein synthesis. Recycling has been shown to occur in the rat brain by the presence of a pool of leucine (and other amino acids) (Seta et ai., 1973; Smith et ai., 1988; Hargreaves-Wall et ai., 1990) and a pool of leucyl-tRNA (Smith et ai., 1988; Hargreaves-Wall et ai., 1990) and valyl-tRNA (Smith et ai., 1991) that do not readily exchange with the plasma. No similar studies have been made with 14C-methyl-or IIC-methyl-Iabeled methionine, although the absence of amino acid recycling has been reported in a recent study using L-esS]methio nine (Grange et ai., 1991a,b).In the present work we examined the fate of L-e4C-methyl]methionine in the plasma and in sev eral regions of the rat brain after systemic infusion. We measured the concentrations of the labeled frac tions, i.e., free methionine, metabolites, and pro teins, and the endogenous content of free methio-

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The rate of incorporation of amino acids into brain proteins during infusion in the rat

Cited by 59 publications

References 23 publications

Ventriculo–cisternal perfusion of twelve amino acids in the rabbit

Ventriculo–cisternal perfusion of twelve amino acids in the rabbit

ACCUMULATION OF HISTIDINE, 3‐METHYLHISTIDINE, AND HOMOCARNOSINE IN THE BRAINS OF PROTEIN‐CALORIE DEFICIENT MONKEYS¹

Regional Cerebral l-[¹⁴C-Methyl]Methionine Incorporation into Proteins: Evidence for Methionine Recycling in the Rat Brain

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The rate of incorporation of amino acids into brain proteins during infusion in the rat

Cited by 59 publications

References 23 publications

Ventriculo–cisternal perfusion of twelve amino acids in the rabbit

Ventriculo–cisternal perfusion of twelve amino acids in the rabbit

ACCUMULATION OF HISTIDINE, 3‐METHYLHISTIDINE, AND HOMOCARNOSINE IN THE BRAINS OF PROTEIN‐CALORIE DEFICIENT MONKEYS1

Regional Cerebral l-[14C-Methyl]Methionine Incorporation into Proteins: Evidence for Methionine Recycling in the Rat Brain

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ACCUMULATION OF HISTIDINE, 3‐METHYLHISTIDINE, AND HOMOCARNOSINE IN THE BRAINS OF PROTEIN‐CALORIE DEFICIENT MONKEYS¹

Regional Cerebral l-[¹⁴C-Methyl]Methionine Incorporation into Proteins: Evidence for Methionine Recycling in the Rat Brain