MODIFICATION OF GLUTAMATE-INDUCED OXIDATIVE STRESS BY LEAD - THE ROLEOF EXTRACELLULAR CALCIUM

The role of extracellular calcium in glutamate-induced oxidative stres s, and the role of glutamatergic neuronal stimulation and oxidative st ress in lead neurotoxicity were explored in mouse hypothalamic GT1-7 c ells. Glutamate increased the production of reactive oxygen species (R O) whether or not extracellular calcium was present. Glutamate-induced ROS production was amplified by lead acetate (PbAc), but only in the absence of extracellular calcium. However, PbAc on its own did not inc rease the production of ROS. A PKC inhibitor (Ro 31-8220) and superoxi de dismutase (SOD) abolished the amplification of glutamate-induced pr oduction of ROS by PbAc, but did not inhibit ROS production induced by glutamate alone. Both glutamate and PbAc decreased the levels of intr acellular glutathione (GSH), and amplified each other's effect on GSH depletion. Glutamate did not decrease cell viability, whereas the cyto toxicity of PbAc was amplified by glutamate. Extracellular calcium, a PKC inhibitor, or SOD did not modify the effects of glutamate, PbAc or their combination on the levels of GSH or cell viability. These data indicate that in GT1-7 cells extracellular calcium is not essential fo r glutamate-induced ROS production, which is amplified by PbAc, but on ly without extracellular calcium. The joint cytotoxicity of glutamate and PbAc is mainly induced by PbAc, preferentially through mechanisms other than ROS production. (C) 1998 Elsevier Science Inc.