Agostinho P, Duarte C B, Oliveira C R
Center for Neurosciences of Coimbra, University of Coimbra, Portugal.
J Neurochem. 1996 Sep;67(3):1153-63. doi: 10.1046/j.1471-4159.1996.67031153.x.
The effect of oxidative stress induced by the oxidant pair ascorbate/Fe2+ on the activity of ionotropic glutamate receptors was studied in cultured chick retina cells. The release of [3H]GABA and the increase of the intracellular free Na+ concentration ([Na+]i), evoked by glutamate receptor agonists, were used as functional assays for the activity of the receptors. The results show that the maximal release of [3H]GABA evoked by kainate (KA; approximately 20% of the total) or AMPA (approximately 11% of the total) was not different in control and peroxidized cells, whereas the EC50 values determined for peroxidized cells (33.6 +/- 1.7 and 8.0 +/- 2.0 microM for KA and AMPA, respectively) were significantly lower than those determined under control conditions (54.1 +/- 6.6 and 13.0 +/- 2.2 microM for KA and AMPA, respectively). The maximal release of [3H]GABA evoked by NMDA under K+ depolarization was significantly higher in peroxidized cells (7.5 +/- 0.5% of the total) as compared with control cells (4.0 +/- 0.2% of the total), and the effect of oxidative stress was significantly reduced by a phospholipase A2 inhibitor or by fatty acid-free bovine serum albumin. The change in the intracellular [Na+]i evoked by saturating concentrations of NMDA under depolarizing conditions was significantly higher in peroxidized cells (8.9 +/- 0.6 mM) than in control cells (5.9 +/- 1.0 mM). KA, used at a subsaturating concentration (35 microM), evoked significantly greater increases of the [Na+]i in peroxidized cells (11.8 +/- 1.7 mM) than in control cells (7.1 +/- 0.8 mM). A saturating concentration (150 microM) of this agonist triggered similar increases of the [Na+]i in control and peroxidized cells. Accordingly, the maximal number of binding sites for (+)-5-[3H]methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10- imine 11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate ([3H]MK-801) was increased after peroxidation, whereas the maximal number of binding sites for [3H]KA was not affected by oxidative stress. These data suggest that under oxidative stress the activity of the ionotropic glutamate receptors is increased, with the NMDA receptor being the most affected by peroxidation.
在培养的鸡视网膜细胞中研究了抗坏血酸盐/Fe2+氧化对离子型谷氨酸受体活性的影响。谷氨酸受体激动剂诱发的[3H]GABA释放和细胞内游离Na+浓度（[Na+]i）的增加被用作受体活性的功能检测指标。结果显示，在对照细胞和过氧化细胞中，由海人酸（KA；约占总量的20%）或AMPA（约占总量的11%）诱发的[3H]GABA最大释放量没有差异，而过氧化细胞中测定的KA和AMPA的半数有效浓度（EC50值）（分别为33.6±1.7和8.0±2.0μM）显著低于对照条件下测定的值（KA和AMPA分别为54.1±6.6和13.0±2.2μM）。在K+去极化条件下，由NMDA诱发的[3H]GABA最大释放量在过氧化细胞中（占总量的7.5±0.5%）显著高于对照细胞（占总量的4.0±0.2%），并且磷脂酶A2抑制剂或无脂肪酸牛血清白蛋白可显著降低氧化应激的影响。在去极化条件下，饱和浓度的NMDA诱发的细胞内[Na+]i变化在过氧化细胞中（8.9±0.6 mM）显著高于对照细胞（5.9±1.0 mM）。以亚饱和浓度（35μM）使用的KA在过氧化细胞中诱发的[Na+]i增加量（11.8±1.7 mM）显著大于对照细胞（7.1±0.8 mM）。该激动剂的饱和浓度（150μM）在对照细胞和过氧化细胞中引发的[Na+]i增加量相似。因此，过氧化后（+）-5-[3H]甲基-10,11-二氢-5H-二苯并[a,d]环庚烯-5,10-亚胺马来酸盐（[3H]MK-801）的最大结合位点数增加，而[3H]KA的最大结合位点数不受氧化应激影响。这些数据表明，在氧化应激下，离子型谷氨酸受体的活性增加，其中NMDA受体受过氧化影响最大。
