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Someya S, Tohyama S, Kameda K, Tanosaki S, Morita Y, Sasaki K, Kang MI, Kishino Y, Okada M, Tani H, Soma Y, Nakajima K, Umei T, Sekine O, Moriwaki T, Kanazawa H, Kobayashi E, Fujita J, Fukuda K. Tryptophan Metabolism Regulates Proliferative Capacity of Human Pluripotent Stem Cells. iScience 2021; 24:102090. [PMID: 33615198 PMCID: PMC7878994 DOI: 10.1016/j.isci.2021.102090] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/09/2020] [Accepted: 01/18/2021] [Indexed: 11/27/2022] Open
Abstract
Human pluripotent stem cells (hPSCs) have a unique metabolic signature for maintenance of pluripotency, self-renewal, and survival. Although hPSCs could be potentially used in regenerative medicine, the prohibitive cost associated with large-scale cell culture presents a major barrier to the clinical application of hPSC. Moreover, without a fully characterized metabolic signature, hPSC culture conditions are not optimized. Here, we performed detailed amino acid profiling and found that tryptophan (TRP) plays a key role in the proliferation with maintenance of pluripotency. In addition, metabolome analyses revealed that intra- and extracellular kynurenine (KYN) is decreased under TRP-supplemented conditions, whereas N-formylkynurenine (NFK), the upstream metabolite of KYN, is increased thereby contributing to proliferation promotion. Taken together, we demonstrate that TRP is indispensable for survival and proliferation of hPSCs. A deeper understanding of TRP metabolism will enable cost-effective large-scale production of hPSCs, leading to advances in regenerative medicine. TRP is the only AA that enables enhanced hPSC proliferation by supplementation hPSCs proliferate with pluripotency after long-term culture in TRP supplementation The proliferative properties of hPSCs are independent of AhR signaling TRP-derived NFK contributes to enhanced hPSC proliferation
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Affiliation(s)
- Shota Someya
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Shugo Tohyama
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan.,Department of Organ Fabrication, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Kotaro Kameda
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Sho Tanosaki
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Yuika Morita
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Kazunori Sasaki
- Human Metabolome Technologies, Inc., Tsuruoka, Yamagata 997-0052, Japan
| | - Moon-Il Kang
- Human Metabolome Technologies, Inc., Tsuruoka, Yamagata 997-0052, Japan
| | - Yoshikazu Kishino
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Marina Okada
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Hidenori Tani
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Yusuke Soma
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Kazuaki Nakajima
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Tomohiko Umei
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Otoya Sekine
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Taijun Moriwaki
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Hideaki Kanazawa
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Eiji Kobayashi
- Department of Organ Fabrication, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Jun Fujita
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan.,Endowed Course for Severe Heart Failure Treatment II, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, Shinjuku, Tokyo 160-8582, Japan
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Abstract
The composition of the free amino acid pools in various brain tumors and in normal brains obtained at surgery or at autopsy is determined with an automatic amino acid analyzer and the results statistically evaluated. The tumors have lower ratios of GABA in the pools than the normal brain; tumors with higher GABA ratios are found in those which are in close contact with and have an invasive nature to brain tissue. In gliomas, the more malignant a tumor becomes, the more different the composition in that tumor is from that in normal brain tissue. But conversely, the ratio of GABA is highest in glioblastoma. The composition of the pool in oligodendroglioma is not significantly different from that in the normal brain. Metastatic brain tumors show the highest ratios of phenylalanine, tyrosine and methionine in the pool among the tumors and the normal brain. From the viewpoint of the composition of the free amino acid pools, like from that of the histological aspects, brain tumors seem to be classified into four groups: glioma, neurinoma, meningioma and metastatic tumors.
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Abstract
Uptake of 1 microM [3H]L-glutamate by cultured 3T3 fibroblasts was strongly dependent on extracellular Na+; it was reduced by elevated concentrations of K+ (60 mM) but it was not influenced by variations in the concentration of Ca2+ (0-9.6 mM). D- and L-Asparate, D- and L-threo-3-hydroxyaspartate DL-threo-3-methylaspartate and a few other glutamate derivatives and analogues inhibited the uptake but several close analogues of L-glutamate (including D-glutamate) had no effect, implying that the uptake system is highly structurally selective. The recently identified inhibitor of glutamate uptake in synaptosomal preparations, L-trans-pyrrolidine-2,4-dicarboxylate, was also among the inhibitors. Apparent Km of the uptake was found to be less than 10 microM. The present observations indicate that Na(+)-dependent 'high-affinity' uptake of L-glutamate may appear in structures which are apparently unrelated to glutamatergic synaptic transmission in the CNS.
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Affiliation(s)
- V J Balcar
- Department of Anatomy, University of Sydney, NSW, Australia
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4
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Pow DV, Baldridge W, Crook DK. Activity-dependent transport of GABA analogues into specific cell types demonstrated at high resolution using a novel immunocytochemical strategy. Neuroscience 1996; 73:1129-43. [PMID: 8809830 DOI: 10.1016/0306-4522(96)00097-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have raised antisera against the GABA analogues gamma-vinyl GABA, diaminobutyric acid and gabaculine. These analogues are thought to be substrates for high-affinity GABA transporters. Retinae were exposed to micromolar concentrations of these analogues in the presence or absence of uptake inhibitors and then fixed and processed for immunocytochemistry at the light and electron microscopic levels. Immunolabelling for gamma-vinyl GABA revealed specific labelling of GABAergic amacrine cells and displaced amacrine cells in retinae of rabbits, cats, chickens, fish and a monkey. GABA-containing horizontal cells of cat and monkey retinae failed to exhibit labelling for gamma-vinyl GABA, suggesting that they lacked an uptake system for this molecule. In light-adapted fish, gamma-vinyl GABA was readily detected in H1 horizontal cells; similar labelling was also observed in light-adapted chicken retinae. The pattern of labelling in the fish and chicken retinae was modified by dark adaptation, when labelling was greatly reduced in the horizontal cells, indicating the activity dependence of GABA (analogue) transport. Intraperitoneal injection of gamma-vinyl GABA into rats resulted in its transport across the blood-brain barrier and subsequent uptake into populations of GABAergic neurons. The other analogues investigated in this study exhibited different patterns of transport; gabaculine was taken up into glial cells, whilst diaminobutyric acid was taken up into neurons, glial cells and retinal pigment epithelia. Thus, these analogues are probably substrates for different GABA transporters. We conclude that immunocytochemical detection of the high-affinity uptake of gamma-vinyl GABA permits the identification of GABAergic neurons which are actively transporting GABA, and suggest that this novel methodology will be a useful tool in rapidly assessing the recent activity of GABAergic neurons at the cellular level.
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Affiliation(s)
- D V Pow
- Department of Physiology and Pharmacology, University of Queensland, Brisbane, Australia
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Griffiths R, Grieve A, Dunlop J, Damgaard I, Fosmark H, Schousboe A. Inhibition by excitatory sulphur amino acids of the high-affinity L-glutamate transporter in synaptosomes and in primary cultures of cortical astrocytes and cerebellar neurons. Neurochem Res 1989; 14:333-43. [PMID: 2569673 DOI: 10.1007/bf01000036] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A detailed kinetic study of the inhibitory effects of L- and D-enantiomers of cysteate, cysteine sulphinate, homocysteine sulphinate, homocysteate, and S-sulpho-cysteine on the neuronal, astroglial and synaptosomal high-affinity glutamate transport system was undertaken. D-[3H] Aspartate was used as the transport substrate. Kinetic characterisation of uptake in the absence of sulphur compounds confirmed the high-affinity nature of the transport systems, the Michaelis constant (Km) for D-aspartate uptake being 6 microM, 21 microM and 84 microM, respectively, in rat brain cortical synaptosomes and primary cultures of mouse cerebellar granule cells and cortical astrocytes. In those cases where significant effects could be demonstrated, the nature of the inhibition was competitive irrespective of the neuronal versus glial systems. The rank order of inhibition was essentially similar in synaptosomes, neurons and astrocytes. Potent inhibition (Ki approximately Km) of transport in each system was exhibited by L-cysteate, and L- and D-cysteine sulphinate whereas substantially weaker inhibitory effects (Ki greater than 10-1000 times the appropriate Km value) were exhibited by the remaining sulphur amino acids. In general, inhibition: (i) was markedly stereospecific in favor of the L-enantiomers (except for cysteine sulphinate) and (ii) was found to decrease with increasing chain length. Computer-assisted molecular modelling studies, in which volume contour maps of the sulphur compounds were superimposed on those of D-aspartate and L-glutamate, demonstrated an order of inhibitory potency which was, qualitatively, in agreement with that obtained quantitatively by in vitro kinetic studies.
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Affiliation(s)
- R Griffiths
- Department of Biochemistry and Microbiology, University of St. Andrews, Fife, Scotland, U.K
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Balcar VJ, Schousboe A, Spoerri PE, Wolff JR. Differences between substrate specificities of l-glutamate uptake by neurons and glia, studied in cell lines and primary cultures. Neurochem Int 1987; 10:213-7. [DOI: 10.1016/0197-0186(87)90130-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/1986] [Accepted: 09/13/1986] [Indexed: 11/28/2022]
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Walum E, Westermark B, Pontén J. Growth dependent induction of high affinity gamma-amino-butyric acid transport in cultures of a normal human brain cell line. Brain Res 1981; 212:215-8. [PMID: 7225857 DOI: 10.1016/0006-8993(81)90054-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Dense, growth inhibited cultures of the human putative glial cell line U-787CG were found to take up gamma-aminobutyric acid (GABA) via a high-affinity transport mechanism (Km = 1.2 microM) not detectable in sparse, rapidly growing cultures. The uptake of GABA was essentially the same in young and old dense cultures indicating that the induction of the high-affinity GABA transport was dependent on cell density and/or growth rate rather than time in culture after trypsinization.
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8
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Martin DL, Shain W. High affinity transport of taurine and beta-alanine and low affinity transport of gamma-aminobutyric acid by a single transport system in cultured glioma cells. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(18)50286-6] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Binding and Iontophoretic Studies on Centrally Active Amino Acids—A Search for Physiological Receptors. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1979. [DOI: 10.1016/s0074-7742(08)60638-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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11
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Hertz L. Functional interactions between neurons and astrocytes I. Turnover and metabolism of putative amino acid transmitters. Prog Neurobiol 1979; 13:277-323. [PMID: 42117 DOI: 10.1016/0301-0082(79)90018-2] [Citation(s) in RCA: 525] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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12
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Stewart RM, Rosenberg RN. Physiology of glia: glial-neuronal interactions. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1979; 21:275-309. [PMID: 43846 DOI: 10.1016/s0074-7742(08)60641-8] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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Hertz L, Schousboe A, Boechler N, Mukerji S, Fedoroff S. Kinetic characteristics of the glutamate uptake into normal astrocytes in cultures. Neurochem Res 1978; 3:1-14. [PMID: 683409 DOI: 10.1007/bf00964356] [Citation(s) in RCA: 188] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Kinetics for uptake and release of glutamate were measured in normal, i.e., nontransformed, astrocytes in cultures obtained from the dissociated, cortex-enriched superficial parts of the brain hemispheres of newborn DBA mice. The uptake kinetics indicated a minor, unsaturable component together with an intense uptake following Michaelis-Menten kinetics. The Km (50 micrometer) was reasonably comparable to the corresponding values in brain slices and in other glial preparations. The Vmax (58.8 nmol min-1 mg-1 protein) was, however, much higher than that observed in glial cell lines or peripheral satellite cells, and also considerably higher than that generally reported for brain slices. The release of glutamate was much smaller than the uptake, and only little affected by an increase of the external glutamate concentration, suggesting a net accumulation of glutamate rather than a homoexchange. Such an intense accumulation of glutamate into normal astrocytes may play a major role in brain metabolism and may help keep the extracellular glutamate concentration below excitatory levels.
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14
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Hösli L, Hösli E. Action and uptake of neurotransmitters in CNS tissue culture. Rev Physiol Biochem Pharmacol 1978; 81:135-88. [PMID: 25483 DOI: 10.1007/bfb0034093] [Citation(s) in RCA: 106] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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15
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16
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Archer EG, Breakefield XO, Sharata MN. Transport of tyrosine, phenylalanine, tryptophan and glycine in neuroblastoma clones. J Neurochem 1977; 28:127-35. [PMID: 833588 DOI: 10.1111/j.1471-4159.1977.tb07718.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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17
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Stewart RM, Martuza RL, Baldessarini RJ, Kornblith PL. Glutamate accumulation by human gliomas and meningiomas in tissue culture. Brain Res 1976; 118:441-52. [PMID: 1009428 DOI: 10.1016/0006-8993(76)90311-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The rapid accumulation of radioactive glutamate was studied in human brain tumor cells grown in tissue culture. The MGH-LM line of human astrocytoma demonstrated both a high (apparent Km = 20 muM) and a low (apparent Km = 0.2 mM) affinity component for the uptake of glutamate. The high affinity component was sodium-, temperature-, and energy-dependent and was present during the confluent (stationary) but not the log phase of cell growth. A study of confluent monolayer cultures of several other human brain tumors revealed that a similar high affinity uptake of glutamate occurred in 7 out of malignant astrocytomas and appeared to be independent of the grade of malignancy. In 3 optic gliomas and 5 meningiomas studied, low but not high affinity uptake of glutamate was found. These studies suggest that glial cells in the human brain may in some instances possess uptake characteristics for glutamate similar to those previously ascribed to nerve endings.
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18
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Orrego F, Miranda R, Saldate C. Electrically induced release of labelled taurine, α- and β-alanine, glycine, glutamate and other amino acids from rat neocortical slicesin vitro. Neuroscience 1976; 1:325-32. [PMID: 11370516 DOI: 10.1016/0306-4522(76)90059-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The electrically induced release of labelled alpha-aminoisobutyrate, L-alpha-alanine, beta-alanine, glycine, histidine, serine, glutamate, aspartate and taurine, from superfused thin slices of the rat neocortex, held on quick-transfer electrodes was studied. In no instance did the release of these substances resemble that of (3H)-labelled noradrenaline, acetylcholine or 5-hydroxytryptamine, which can be released by 0.5-3 V stimuli and whose release shows an absolute dependency on calcium ions. Small amounts of alpha-aminoisobutyrate, beta-alanine, serine, glutamate and aspartate were released with 4 V stimuli, but the release was statistically significant for the first two substances only. Following incubation with (3H)-histidine, substantial labelling of homocarnosine was found, but no electrically induced release of this dipeptide could be detected. With (14C)-taurine, however, small but significant release was found with sinewave stimuli of 1.5 V or higher. Such release was significantly increased in the absence of calcium ions. Biphasic pulses of frequencies ranging between 10 and 100 Hz. (1 V, 3 ms duration) did not evoke the release of (14C)-taurine, although this type of stimulation readily induced the release of (3H)-noradrenaline studied simultaneously. Differences in threshold, calcium dependency and shape of the taurine efflux peak, relative to that seen with (3H)-noradrenaline and other transmitters, suggest that taurine release occurs by mechanisms unrelated to those that mediate transmitter secretion. The release of all the above amino acids can readily be elicited, however, if stimuli that are too intense, prolonged or damaging are utilized. The occurrence of these artifacts in the present and in previous work is discussed.
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Affiliation(s)
- F Orrego
- Department of Biochemistry, Instituto Nacional de Cardiología, México 7, D.F
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19
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Abstract
The accumulation of L[14C]glutamate by the isolated rat retina has been studied. When retinae were incubated at 37 degrees C in a medium containing L-[14C]glutamate, tissue/medium ratios of about 40:1 were achieved after 60 min. The labelled L-glutamate was rapidly metabolised and after 10 min about 50% of the radioactivity in the tissue amino acids was present as glutamine, aspartate, and 4-aminobutyrate (GABA). The process responsible for L-glutamate uptake showed many of the properties of an active uptake system: it was temperature sensitive, sodium dependent, inhibited by metabolic inhibitors and showed saturation kinetics. The saturable uptake process could be resolved into two components; a 'high' affinity process (apparent Km = 21 muM, Vmax = 35 nmoles/min/g tissue) and a 'low' affinity process (Km = 630 muM, Vmax = 881 nmoles/min/g tissue). The 'high' affinity and 'low' affinity uptake processes for L-glutamate appeared to have identical properties in the retina. The uptake of L-glutamate was not specific and was inhibited by other acidic amino acids including D-glutamate but not by neutral or basic amino acids. The retinal uptake of L-glutamate is not likely to be due to a homoexchange phenomenon because the retina was capable of achieving a large net uptake of glutamate and the efflux of L-[14C]glutamate from the tissue was not increased by the addition of non-radioactive L-glutamate to the incubation medium. Autoradiographic studies indicated that the sites for glutamate uptake are largely in the neuroglial Muller cells.
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20
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Beart PM. An evaluation of L-glutamate as the transmitter released from optic nerve terminals of the pigeon. Brain Res 1976; 110:99-114. [PMID: 6128 DOI: 10.1016/0006-8993(76)90211-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The possibility was investigated that L-glutamic acid is the excitatory transmitter released from the optic nerve terminals of the pigeon optic tectum. (1) Superficial layers of the tectum contained high levels of endogenous glutamate and accumulated L-[3H]glutamate by a high affinity uptake process. (2) Subcellular and autoradiographic studies indicated that 10-30% of the exogenously accumulated L-[3H]glutamate was localized within synaptosomes, and that 11-15% of the synaptosomes had been labelled. (3) The glutamate-accumulating synaptosomes sedimented to the same isopycnic density as pinched-off optic nerve terminals. (4) GABA-and noradrenaline-accumulating synaptosomes were also associated with this subcellular population. (5) Retinal ablation did not change endogenous glutamate concentrations or the high affinity uptake of glutamate. The results are discussed in relation to a possible role for L-glutamate as the 'optic nerve transmitter' and in the context of previous evidence implicating glutamate as an excitatory transmitter.
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22
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Lasher RS. Uptake of GABA by neuronal and nonneuronal cells in dispersed cell cultures of postnatal rat cerebellum. JOURNAL OF NEUROBIOLOGY 1975; 6:597-608. [PMID: 1237537 DOI: 10.1002/neu.480060606] [Citation(s) in RCA: 43] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A study was made of the time course and kinetics of [3H]GABA uptake by dispersed cell cultures of postnatal rat cerebellum with and without neuronal cells. The properties of GABA neurons were calculated from the biochemical difference between the two types of cultures. It was found that for any given concentration of [3H]GABA, or any time up to 20 min, GABA neurons in cultures 21 days in vitro had an average velocity of uptake several orders of magnitude greater than that of nonneuronal cells. In addition, the apparent Kmvalues for GABA neurons for high and low affinity uptake were 0.33 X 10(-6) M and 41.8 X 10(-4) M, respectively. For nonneuronal cells, the apparent Km for high affinity uptake was 0.29 X 10(-6) M. The apparent Vmax values for GABA neurons for high and low affinity uptake were 28.7 X 10(-6) mol/g DNA/min and 151.5 mmol/g DNA/min, respectively. For nonneuronal cells, the apparent Vmax for high affinity uptake was 0.06 X 10(-6) mol/g DNA/min. No low affinity uptake system for nonneuronal cells could be detected after correcting the data for binding and diffusion. By substituting the apparent kinetic constants in the Michaelis-Menten equation, it was determined that for GABA concentrations of 5 X 10(-9) M to 1 mM or higher over 99% of the GABA should be accumulated by GABA neurons, given equal access of all cells to the label. In addition, high affinity uptake of [3H]GABA by GABA neurons was completely blocked by treatment with 0.2 mM ouabain, whereas that by noneuronal cells was only slightly decreased. Most (75-85%) of the [3H]GABA (4.4 X 10(-6) M) uptake by both GABA neurons and nonneuronal cells was sodium and temperature dependent.
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Iversen LL, Kelly JS. Uptake and metabolism of gamma-aminobutyric acid by neurones and glial cells. Biochem Pharmacol 1975; 24:933-8. [PMID: 1156449 DOI: 10.1016/0006-2952(75)90422-0] [Citation(s) in RCA: 502] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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24
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Schon F, Beart PM, Chapman D, Kelly JS. On GABA metabolism in the gliocyte cells of the rat pineal gland. Brain Res 1975; 85:479-90. [PMID: 234281 DOI: 10.1016/0006-8993(75)90821-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The uptake of the inhibitory transmitter substance gamma-aminobutyric acid (GABA) into the adult rat pineal gland was studied autoradiographically using both light and electron microscopy. The sites of GABA uptake were shown to be exclusively present in the gliocyte cells of the gland following both in vitro incubation with tritiated GABA and after in vivo administration of the amino acid by intra-arterial injection. Both the pinealocyte cells and the numerous sympathetic axons in the gland were devoid of silver grains. Preliminary biochemical studies indicated that the gliocyte uptake process for GABA resembles that in the satellite glia of the sensory ganglia but differed from that in slices of the cerebral cortex. Evidence is also presented which shows the pineal gland to contain endogenous GABA and the enzymes directly associated with its in vivo metabolism, L-glutamate-1-carboxylase (EC 4.1.1.15) (GAD) and GABA-2-oxoglutarate aminotransferase (EC 2.6.1.19) (GABA-T). Furthermore, a 3-fold rise in endogenous GABA occurred in the pineal after inhibition of GABA-catabolism as would be expected if the GABA-shunt pathway was functionally active in the oxidative metabolism of the pineal gland.
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