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 language | English |
|---|---|
| Pages (from-to) | 386-392 |
| Number of pages | 7 |
| Journal | Current Eye Research |
| Volume | 23 |
| Issue number | 5 |
| DOIs | |
| State | Published - 2001 |
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All Science Journal Classification (ASJC) codes
- Ophthalmology
- Sensory Systems
Cite this
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 journal › Article
}
TY - JOUR
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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UR - http://www.scopus.com/inward/citedby.url?scp=0036205016&partnerID=8YFLogxK
U2 - 10.1076/ceyr.23.5.386.5443
DO - 10.1076/ceyr.23.5.386.5443
M3 - Article
VL - 23
SP - 386
EP - 392
JO - Current Eye Research
JF - Current Eye Research
SN - 0271-3683
IS - 5
ER -