Oxidized glutathione modulates N-methyl-D-aspartate- and depolarization-induced increases in intracellular Ca2+ in...

We have investigated the interaction of reduced and oxidized glutathione (GSSG) with intracellular Ca2+ increases produced by N-methyl-D-aspartate (NMDA), kainate and KCl in primary cultures of forebrain neurons derived from fetal rats. Responses to NMDA, applied with glycine, were inhibited by GSSG (10 mM), but were unaffected by reduced glutathione and L-cysteine. Inhibition by GSSG was still apparent after cells were oxidized by 5,5'-dithio-bis-2-nitrobenzoic acid, and this effect showed spontaneous but only partial reversal. This suggests that modulation of the redox site on the NMDA receptor could not account for all of the effects produced by GSSG. However, the observation that complete recovery from GSSG treatment required exposure of cells to dithiothreitol suggests that oxidation of the redox site contributes to the action of GSSG. GSSG also inhibited responses produced by 50 mM KCl but not those produced by 50 microM kainate. The effects of GSSG on KCl responses were fully and rapidly reversible. These results suggest that high concentrations of GSSG may modulate NMDA receptors, and that some of the actions of GSSG may be mediated by the redox site on the receptor complex.