Hypoxia-induced [3H]D-aspartate release from isolated bovine retina

Modulation by calcium-channel blockers and glutamatergic agonists and antagonists

Sunny E. Ohia, S. Olubusayo Awe, Catherine A. Opere, Angela M. LeDay, Lydia C. Harris, Najam A. Sharif

Research output: Contribution to journalArticle

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Abstract

Purpose. The aim of the present study was two-fold: (a) to examine the effect of hypoxia on [3H]D-aspartate release from isolated bovine and human retinae, and (b) to investigate the regulation of hypoxia-induced neurotransmitter release by glutamate receptor agonists and antagonists. Methods. Isolated neural retinae were incubated in oxygenated Krebs buffer solution containing [3H]D-aspartate and then prepared for studies of neurotransmitter release using the superfusion method. Release of [3H]D-aspartate was evoked by K+ (50 mM) applied at 90 minutes (S1) and hypoxia (induced by exposure of tissues to solutions pre-gassed with 95% N2: 5% CO2 for 60 minutes) at 108 minutes (S2) after onset of superfusion. Results. Under hypoxic conditions, pO2 in normal Krebs buffer solution was reduced from 14.53 ± 0.26ppm (n = 6) to 0.54 ± 0.04ppm (n = 9) after one hour of gassing with 95% N2: 5% CO2. Exposure to hypoxia elicited an overflow of [3H]D-aspartate yielding S2/S1 ratios of 0.62 ± 0.06 (n = 12) and 0.54 ± 0.03 (n = 8) in bovine and human tissues respectively. In isolated bovine retinae, L- and N-calcium-channel antagonists diltiazem, nitrendipine, verapamil and ω-conotoxin significantly (p <0.01 or higher) attenuated hypoxia-induced [3H]D-aspartate release. L-glutamate (30 μM) significantly (p <0.001) potentiated hypoxia-induced [3H]D-aspartate release whereas kainate (30 μM) inhibited this response. NMDA (in concentrations up to 1 mM) had no effect on hypoxia-induced [3H]D-aspartate release. Antagonists of glutamate receptors and the polyamine site on the NMDA receptor inhibited hypoxia-induced release of [3H]D-aspartate in bovine retina with the following rank order of activity: ifenprodil ≅ MCPG > L-AP3 > MK-801. At an equimolar concentration (10 μM), L-AP3 but not ifenprodil, MCPG, MK 801 or arcaine, caused a significant (p <0.001) inhibition of hypoxia-induced [3H]D-aspartate release from human retinae. Conclusions. Hypoxia can induce the release of [3H]D-aspartate from isolated bovine retinae by a calcium-dependent process. Hypoxia-induced [3H]D-aspartate release from isolated bovine retinae can be regulated by glutamate receptor agonists/antagonists and blockers of polyamine site on the NMDA receptor.

Original languageEnglish
Pages (from-to)386-392
Number of pages7
JournalCurrent Eye Research
Volume23
Issue number5
DOIs
StatePublished - 2001

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D-Aspartic Acid
Calcium Channel Blockers
Retina
Excitatory Amino Acid Agonists
Excitatory Amino Acid Antagonists
Dizocilpine Maleate
Neurotransmitter Agents
Buffers
Conotoxins
Nitrendipine
Diltiazem
Polyamines
Verapamil
Hypoxia
N-Methyl-D-Aspartate Receptors
Calcium

All Science Journal Classification (ASJC) codes

  • Ophthalmology
  • Sensory Systems

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Hypoxia-induced [3H]D-aspartate release from isolated bovine retina : Modulation by calcium-channel blockers and glutamatergic agonists and antagonists. / Ohia, Sunny E.; Awe, S. Olubusayo; Opere, Catherine A.; LeDay, Angela M.; Harris, Lydia C.; Sharif, Najam A.

In: Current Eye Research, Vol. 23, No. 5, 2001, p. 386-392.

Research output: Contribution to journalArticle

Ohia, Sunny E. ; Awe, S. Olubusayo ; Opere, Catherine A. ; LeDay, Angela M. ; Harris, Lydia C. ; Sharif, Najam A. / Hypoxia-induced [3H]D-aspartate release from isolated bovine retina : Modulation by calcium-channel blockers and glutamatergic agonists and antagonists. In: Current Eye Research. 2001 ; Vol. 23, No. 5. pp. 386-392.
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abstract = "Purpose. The aim of the present study was two-fold: (a) to examine the effect of hypoxia on [3H]D-aspartate release from isolated bovine and human retinae, and (b) to investigate the regulation of hypoxia-induced neurotransmitter release by glutamate receptor agonists and antagonists. Methods. Isolated neural retinae were incubated in oxygenated Krebs buffer solution containing [3H]D-aspartate and then prepared for studies of neurotransmitter release using the superfusion method. Release of [3H]D-aspartate was evoked by K+ (50 mM) applied at 90 minutes (S1) and hypoxia (induced by exposure of tissues to solutions pre-gassed with 95{\%} N2: 5{\%} CO2 for 60 minutes) at 108 minutes (S2) after onset of superfusion. Results. Under hypoxic conditions, pO2 in normal Krebs buffer solution was reduced from 14.53 ± 0.26ppm (n = 6) to 0.54 ± 0.04ppm (n = 9) after one hour of gassing with 95{\%} N2: 5{\%} CO2. Exposure to hypoxia elicited an overflow of [3H]D-aspartate yielding S2/S1 ratios of 0.62 ± 0.06 (n = 12) and 0.54 ± 0.03 (n = 8) in bovine and human tissues respectively. In isolated bovine retinae, L- and N-calcium-channel antagonists diltiazem, nitrendipine, verapamil and ω-conotoxin significantly (p <0.01 or higher) attenuated hypoxia-induced [3H]D-aspartate release. L-glutamate (30 μM) significantly (p <0.001) potentiated hypoxia-induced [3H]D-aspartate release whereas kainate (30 μM) inhibited this response. NMDA (in concentrations up to 1 mM) had no effect on hypoxia-induced [3H]D-aspartate release. Antagonists of glutamate receptors and the polyamine site on the NMDA receptor inhibited hypoxia-induced release of [3H]D-aspartate in bovine retina with the following rank order of activity: ifenprodil ≅ MCPG > L-AP3 > MK-801. At an equimolar concentration (10 μM), L-AP3 but not ifenprodil, MCPG, MK 801 or arcaine, caused a significant (p <0.001) inhibition of hypoxia-induced [3H]D-aspartate release from human retinae. Conclusions. Hypoxia can induce the release of [3H]D-aspartate from isolated bovine retinae by a calcium-dependent process. Hypoxia-induced [3H]D-aspartate release from isolated bovine retinae can be regulated by glutamate receptor agonists/antagonists and blockers of polyamine site on the NMDA receptor.",
author = "Ohia, {Sunny E.} and Awe, {S. Olubusayo} and Opere, {Catherine A.} and LeDay, {Angela M.} and Harris, {Lydia C.} and Sharif, {Najam A.}",
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T1 - Hypoxia-induced [3H]D-aspartate release from isolated bovine retina

T2 - Modulation by calcium-channel blockers and glutamatergic agonists and antagonists

AU - Ohia, Sunny E.

AU - Awe, S. Olubusayo

AU - Opere, Catherine A.

AU - LeDay, Angela M.

AU - Harris, Lydia C.

AU - Sharif, Najam A.

PY - 2001

Y1 - 2001

N2 - Purpose. The aim of the present study was two-fold: (a) to examine the effect of hypoxia on [3H]D-aspartate release from isolated bovine and human retinae, and (b) to investigate the regulation of hypoxia-induced neurotransmitter release by glutamate receptor agonists and antagonists. Methods. Isolated neural retinae were incubated in oxygenated Krebs buffer solution containing [3H]D-aspartate and then prepared for studies of neurotransmitter release using the superfusion method. Release of [3H]D-aspartate was evoked by K+ (50 mM) applied at 90 minutes (S1) and hypoxia (induced by exposure of tissues to solutions pre-gassed with 95% N2: 5% CO2 for 60 minutes) at 108 minutes (S2) after onset of superfusion. Results. Under hypoxic conditions, pO2 in normal Krebs buffer solution was reduced from 14.53 ± 0.26ppm (n = 6) to 0.54 ± 0.04ppm (n = 9) after one hour of gassing with 95% N2: 5% CO2. Exposure to hypoxia elicited an overflow of [3H]D-aspartate yielding S2/S1 ratios of 0.62 ± 0.06 (n = 12) and 0.54 ± 0.03 (n = 8) in bovine and human tissues respectively. In isolated bovine retinae, L- and N-calcium-channel antagonists diltiazem, nitrendipine, verapamil and ω-conotoxin significantly (p <0.01 or higher) attenuated hypoxia-induced [3H]D-aspartate release. L-glutamate (30 μM) significantly (p <0.001) potentiated hypoxia-induced [3H]D-aspartate release whereas kainate (30 μM) inhibited this response. NMDA (in concentrations up to 1 mM) had no effect on hypoxia-induced [3H]D-aspartate release. Antagonists of glutamate receptors and the polyamine site on the NMDA receptor inhibited hypoxia-induced release of [3H]D-aspartate in bovine retina with the following rank order of activity: ifenprodil ≅ MCPG > L-AP3 > MK-801. At an equimolar concentration (10 μM), L-AP3 but not ifenprodil, MCPG, MK 801 or arcaine, caused a significant (p <0.001) inhibition of hypoxia-induced [3H]D-aspartate release from human retinae. Conclusions. Hypoxia can induce the release of [3H]D-aspartate from isolated bovine retinae by a calcium-dependent process. Hypoxia-induced [3H]D-aspartate release from isolated bovine retinae can be regulated by glutamate receptor agonists/antagonists and blockers of polyamine site on the NMDA receptor.

AB - Purpose. The aim of the present study was two-fold: (a) to examine the effect of hypoxia on [3H]D-aspartate release from isolated bovine and human retinae, and (b) to investigate the regulation of hypoxia-induced neurotransmitter release by glutamate receptor agonists and antagonists. Methods. Isolated neural retinae were incubated in oxygenated Krebs buffer solution containing [3H]D-aspartate and then prepared for studies of neurotransmitter release using the superfusion method. Release of [3H]D-aspartate was evoked by K+ (50 mM) applied at 90 minutes (S1) and hypoxia (induced by exposure of tissues to solutions pre-gassed with 95% N2: 5% CO2 for 60 minutes) at 108 minutes (S2) after onset of superfusion. Results. Under hypoxic conditions, pO2 in normal Krebs buffer solution was reduced from 14.53 ± 0.26ppm (n = 6) to 0.54 ± 0.04ppm (n = 9) after one hour of gassing with 95% N2: 5% CO2. Exposure to hypoxia elicited an overflow of [3H]D-aspartate yielding S2/S1 ratios of 0.62 ± 0.06 (n = 12) and 0.54 ± 0.03 (n = 8) in bovine and human tissues respectively. In isolated bovine retinae, L- and N-calcium-channel antagonists diltiazem, nitrendipine, verapamil and ω-conotoxin significantly (p <0.01 or higher) attenuated hypoxia-induced [3H]D-aspartate release. L-glutamate (30 μM) significantly (p <0.001) potentiated hypoxia-induced [3H]D-aspartate release whereas kainate (30 μM) inhibited this response. NMDA (in concentrations up to 1 mM) had no effect on hypoxia-induced [3H]D-aspartate release. Antagonists of glutamate receptors and the polyamine site on the NMDA receptor inhibited hypoxia-induced release of [3H]D-aspartate in bovine retina with the following rank order of activity: ifenprodil ≅ MCPG > L-AP3 > MK-801. At an equimolar concentration (10 μM), L-AP3 but not ifenprodil, MCPG, MK 801 or arcaine, caused a significant (p <0.001) inhibition of hypoxia-induced [3H]D-aspartate release from human retinae. Conclusions. Hypoxia can induce the release of [3H]D-aspartate from isolated bovine retinae by a calcium-dependent process. Hypoxia-induced [3H]D-aspartate release from isolated bovine retinae can be regulated by glutamate receptor agonists/antagonists and blockers of polyamine site on the NMDA receptor.

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