Efflux from isolated rat retina of amino acids formed from different substrates

The purpose of the present experiments was to evaluate the contribution of the glutamate-glutamine cycle in retinal glial (Müller) cells to photoreceptor cell synaptic transmission. Dark-adapted isolated rat retinas were superfused with oxygenated bicarbonate-buffered media. Recordings were made of the b-wave of the electroretinogram as a measure of light-induced photoreceptor to ON-bipolar neuron transmission. L-methionine sulfoximine (1–10 mM) was added to superfusion media to inhibit glutamine synthetase, a Müller cell specific enzyme, by more than 99% within 5–10 min, thereby disrupting the conversion of glutamate to glutamine in the Müller cells. Threo-hydroxyaspartic acid and D-aspartate were used to block glutamate transporters. The amplitude of the b-wave was well maintained for 1–2 h provided 0.25 mM glutamate or 0.25 mM glutamine was included in the media. Without exogenous glutamate or glutamine the amplitude of the b-wave declined by about 70% within 1 h. Inhibition of glutamate transporters led to a rapid (2–5 min) reversible loss of the b-wave in the presence and absence of the amino acids. In contrast, inhibition of glutamine synthetase did not alter significantly either the amplitude of the b-wave in the presence of glutamate or glutamine or the rate of decline of the b-wave found in the absence of these amino acids. Excellent recovery of the b-wave was found when 0.25 mM glutamate was resupplied to L-methionine sulfoximine–treated retinas. The results suggest that in the isolated rat retina uptake of released glutamate into photoreceptors plays a more important role in transmitter recycling than does uptake of glutamate into Müller cells and its subsequent conversion to glutamine.

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The effect of light and potassium depolarization on the release of endogenous amino acids from the isolated rat retina

Experimental Eye Research ◽

10.1016/0014-4835(78)90153-7 ◽

1978 ◽

Vol 26 (1) ◽

pp. 71-75 ◽

Cited By ~ 24

Author(s):

A.J. Kennedy ◽

M.J. Neal

Keyword(s):

Amino Acids ◽

Potassium Depolarization ◽

Rat Retina ◽

Endogenous Amino Acids ◽

Isolated Rat ◽

Effect Of Light

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Exogenous glutamate and taurine exert differential actions on light-induced release of two endogenous amino acids in isolated rat retina

Journal of Neuroscience Research ◽

10.1002/jnr.10697 ◽

2003 ◽

Vol 73 (5) ◽

pp. 731-736 ◽

Cited By ~ 3

Author(s):

Péter Barabás ◽

Ilona Kovács ◽

Julianna Kardos ◽

Arne Schousboe

Keyword(s):

Amino Acids ◽

Rat Retina ◽

Endogenous Amino Acids ◽

Isolated Rat

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Characteristics of system ASC for transport of neutral amino acids in the isolated rat hepatocyte.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)69607-9 ◽

1981 ◽

Vol 256 (7) ◽

pp. 3304-3312

Author(s):

M.S. Kilberg ◽

M.E. Handlogten ◽

H.N. Christensen

Keyword(s):

Amino Acids ◽

Rat Hepatocyte ◽

Neutral Amino Acids ◽

Isolated Rat

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In vitro adsorption of amino acids onto isolated rat erythrocyte membranes

The International Journal of Biochemistry & Cell Biology ◽

10.1016/1357-2725(95)00049-u ◽

1995 ◽

Vol 27 (8) ◽

pp. 761-765 ◽

Cited By ~ 6

Author(s):

Catalina Pico ◽

Antoni Pons ◽

Andreu Palou

Keyword(s):

Amino Acids ◽

Erythrocyte Membranes ◽

Isolated Rat

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Lipid Peroxidation Effects on Isolated Rat Retina

Oxygen Transport to Tissue—VI - Advances in Experimental Medicine and Biology ◽

10.1007/978-1-4684-4895-5_82 ◽

1984 ◽

pp. 847-852 ◽

Cited By ~ 1

Author(s):

Pierre Braquet ◽

Michel Doly ◽

Rene Bourgain

Keyword(s):

Lipid Peroxidation ◽

Rat Retina ◽

Isolated Rat

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Transamination of branched-chain keto acids by isolated perfused rat kidney.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1978.235.1.e47 ◽

1978 ◽

Vol 235 (1) ◽

pp. E47

Author(s):

W E Mitch ◽

W Chan

Keyword(s):

Amino Acids ◽

Rat Kidney ◽

Branched Chain Amino Acids ◽

Keto Acid ◽

Branched Chain Amino Acid ◽

Keto Acids ◽

Perfused Rat Kidney ◽

Branched Chain ◽

Branched Chain Keto Acids ◽

Isolated Rat

Isolated rat kidney perfused without substrate released serine, glycine, and taurine, and substantially smaller amounts of other amino acids. When branched-chain keto acids were added, the corresponding amino acids were released at rates amounting to 15-25% of keto acid disappearance. Perfusion with 2 mM alpha-keto-isovalerate or alpha-keto-beta-methylvalerate caused an increased glucose release amounting to 18-23% of keto acid disappearance. The activity of branched-chain amino acid transferase (BATase) was significantly stimulated by perfusion with the analogue of leucine, but not by perfusion with alpha-ketoglutarate, the analogues of valine or isoleucine, or with leucine itself. These findings document that the kidney converts branched-chain keto acids in part to the corresponding amino acids and suggest that the keto analogue of leucine may be involved in the control of renal BATase activity, thereby indirectly regulating the metabolism of branched-chain amino acids.

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