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.
N1 - Funding Information:
The authors thank Nebraska Lions Eye Bank and both J.F. O’Neill and Greater Omaha Packing Companies, Omaha for their generous donations of human and cow eyeballs, respectively. The authors also thank Ms. Kathy Widman for her excellent secretarial assistance. This project was supported by a grant from Alcon Research, Ltd. (Fort Worth, TX). The critical review of the manuscript and helpful comments of Dr. M.R. Hellberg are appreciated.
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.
UR - http://www.scopus.com/inward/record.url?scp=0036205016&partnerID=8YFLogxK
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
C2 - 11910529
AN - SCOPUS:0036205016
VL - 23
SP - 386
EP - 392
JO - Current Eye Research
JF - Current Eye Research
SN - 0271-3683
IS - 5
ER -