Ammonia Metabolism

Tsukada, Yasuzo

doi:10.1007/978-1-4615-7166-7_6

Cited by 9 publications

(8 citation statements)

References 54 publications

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“…Neurons signal to astrocytes and other glial cells via a large number of molecules including many neurotransmitters (Mudrick‐Donnon et al ., 1993; Porter & McCarthy, 1996; Kulik et al ., 1999), and also K + (Rose & Deitmer, 1995) and ammonium (Poitry et al ., 2000). Ammonium is released from active nervous tissue (Tashiro, 1922; Tsukada, 1971; Tsacopoulos et al ., 1997). In rat brain, exogenous ammonium is taken up by astrocytes and incorporated mainly in glutamine (Cooper et al ., 1979; Norenberg & Martinez‐Hernandez, 1979).…”

Section: Introductionmentioning

confidence: 99%

Neuron–glial trafficking of NH₄⁺ and K⁺: separate routes of uptake into glial cells of bee retina

Marcaggi

Jeanne

Coles

2004

Eur J of Neuroscience

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Ammonium (NH4+ and/or NH3) and K+ are released from active neurons and taken up by glial cells, and can modify glial cell behaviour. Study of these fluxes is most advanced in the retina of the honeybee drone, which consists essentially of identical neurons (photoreceptors) and identical glial cells (outer pigment cells). In isolated bee retinal glial cells, ammonium crosses the membrane as NH4+ on a Cl- cotransporter. We have now investigated, in the more physiological conditions of a retinal slice, whether the NH4+-Cl- cotransporter can transport K+ and whether the major K+ conductance can transport NH4+. We increased [NH4+] or [K+] in the superfusate and monitored uptake by recording from the glial cell syncytium or from interstitial space with microelectrodes selective for H+ or K+. In normal superfusate solution, ammonium acidified the glial cells but, after 6 min superfusion in low [Cl-] solution, ammonium alkalinized them. In the same low [Cl-] conditions, the rise in intraglial [K+] induced by an increase in superfusate [K+] was unchanged, i.e. no K+ flux on the Cl- cotransporter was detected. Ba2+ (5 mm) abolished the glial depolarization induced by K+ released from photoreceptors but did not reduce NH4+uptake. We estimate that when extracellular [NH4+] is increased, 62-100% is taken up by the NH4+-Cl- cotransporter and that when K+ is increased, 77-100% is taken up by routes selective for K+. This separation makes it possible that the glial uptake of NH4+ and of K+, and hence their signalling roles, might be regulated separately.

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Section: Introductionmentioning

confidence: 99%

Neuron–glial trafficking of NH₄⁺ and K⁺: separate routes of uptake into glial cells of bee retina

Marcaggi

Jeanne

Coles

2004

Eur J of Neuroscience

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“…However its effect on the total COz fixed by that tissue was not reported. The possible relevance of such an interrelation to the neurological and neuropsychiatric effects of hyperammonemia resulting from liver disease (Tsukada, 1972) is speculative but intriguing.…”

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confidence: 98%

“…Whether the latter process occurs in the CNS has been the subject of considerable investigation (Buniatian, 1972) with no definitive answers as yet. Three of these processes are concerned with removal of ammonia whose neurotoxic effects are well known (Tsukada, 1972). Furthermore, carbon dioxide or bicarbonate per se stabilize peripheral nerve membrane (Monnier, 1952) while cerebral excitability is dependent on COz and ammonia levels (Pincus, 1969;Nair and Bau, 1971).…”

mentioning

confidence: 98%

“…Furthermore, carbon dioxide or bicarbonate per se stabilize peripheral nerve membrane (Monnier, 1952) while cerebral excitability is dependent on COz and ammonia levels (Pincus, 1969;Nair and Bau, 1971). Though both COz fixation and ammonia metabolism by nervous tissue have been recently reviewed (Cheng, 1971;Tsukada, 1972), few reports have dealt with the effect of ammonia on the fixation of CO, by nerve tissue. Crane and Ball (1951) using freshly excised duck and cattle retina, showed ammonia t o have a definite inhibitory effect on the incorporation of 14C02 into pyruvate.…”

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confidence: 99%

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The effect of ammonium salts on carbon dioxide fixation by cultured and freshly excised central nervous tissue

1973

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“…Ammonium ions play various roles in the nervous system [1,2]. Under physiological conditions, the ammonia level in the brain is elevated during neural activity.…”

Section: Introductionmentioning

confidence: 99%

In vivo Investigation of Glutamate–Glutamine Metabolism in Hyperammonemic Monkey Brain Using <sup>13</sup>C-Magnetic Resonance Spectroscopy

et al. 1998

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To investigate the metabolism of glutamate and glutamine in living monkey brain, a system of in vivo ¹³C magnetic resonance spectroscopy (MRS) using ¹H-decoupled ¹³C spectroscopy combined with monitoring temperature changes in the brain by MR phase mapping was developed. Serial ¹³C-NMR spectra of the amino acids glutamate and glutamine were acquired non-invasively over 4 h from anesthetized monkey brain after the intravenous administration of [1-¹³C]glucose (0.5–1.0 g/kg). In the acute hyperammonemic state induced by the administration of ammonium acetate (77 mg/kg bolus), it was observed that ¹³C incorporation into glutamine-4 was clearly accelerated, without changes of ¹³C incorporation into glutamate-4. During hyperammonemia, it was shown directly by [2-¹³C]glucose administration that the anaplerotic pathway for the TCA cycle was also augmented, contributing to the formation of glutamine in the astroglia.

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Ammonia Metabolism

Cited by 9 publications

References 54 publications

Neuron–glial trafficking of NH₄⁺ and K⁺: separate routes of uptake into glial cells of bee retina

Neuron–glial trafficking of NH₄⁺ and K⁺: separate routes of uptake into glial cells of bee retina

The effect of ammonium salts on carbon dioxide fixation by cultured and freshly excised central nervous tissue

In vivo Investigation of Glutamate–Glutamine Metabolism in Hyperammonemic Monkey Brain Using <sup>13</sup>C-Magnetic Resonance Spectroscopy

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Ammonia Metabolism

Cited by 9 publications

References 54 publications

Neuron–glial trafficking of NH4+ and K+: separate routes of uptake into glial cells of bee retina

Neuron–glial trafficking of NH4+ and K+: separate routes of uptake into glial cells of bee retina

The effect of ammonium salts on carbon dioxide fixation by cultured and freshly excised central nervous tissue

In vivo Investigation of Glutamate–Glutamine Metabolism in Hyperammonemic Monkey Brain Using <sup>13</sup>C-Magnetic Resonance Spectroscopy

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Neuron–glial trafficking of NH₄⁺ and K⁺: separate routes of uptake into glial cells of bee retina

Neuron–glial trafficking of NH₄⁺ and K⁺: separate routes of uptake into glial cells of bee retina