Glutamic acid reverses Pb2+-induced reductions of NMDA receptor subunits in vitro

The objective of this study is to determine the effects of Pb2+ on N-methyl-d-aspartate receptor (NMDAR) subunits—NR1C1, NR2A and NR2B in primary cultured neuronal cells. We hypothesize that l-glutamic acid (GA) reverses Pb2+-induced NMDAR damage. Neuronal cells were isolated from the fetus brain at 18–20th day of gestation of pregnant Sprague Dawley (SD) rats. All experiments were included three independent cell preparations (N = 3). The neuronal cells were exposed to Pb2+ (10−10, 10−9, 10−8 and 10−7 M) for 24 h. Neurons were pretreated with NMDAR agonist—l-glutamic acid (GA) (200 μM) and antagonists dizocipine (MK-801, 50 nM) for 1 h and then exposed to 10−7 M of Pb2+ for 24 h. Finally, GA at 2, 0.2 and 0.02 mM was incubated with neurons prior to Pb2+ exposure. Aliquots of NR1, NR2A and NR2B proteins from cell homogenate were immunoprecipitated with protein A agarose and detected by Western blotting. The addition of GA unconventionally reversed the reductions of NMDAR by Pb at protein levels, whereas MK-801 exacerbated Pb2+-induced damage. The protection by GA against Pb2+-induced reduction of NMDAR was dose-dependent. These findings suggest that the administration of GA may be a potential approach to intervene the Pb2+-induced NMDAR alterations.