Hydrochloric acid alters the effect of l-glutamic acid on cell viability in human neuroblastoma cell cultures

l-Glutamic acid (l-glutamate) is used to induce excitotoxicity and test neuroprotective compounds in cell cultures. However, because l-glutamate powder is nearly insoluble in water, many manufacturers recommend reconstituting l-glutamate in hydrochloric acid (HCl) prior to successive dilutions. Nevertheless, HCl, even at low concentrations, may alter the pH of the cell culture medium and interfere with cell activity. Thus, the aim of this study was to evaluate whether the reconstitution of l-glutamate powder in HCl alters its capacity to induce neurotoxicity in different human neuroblastoma cell lines. SH-SY5Y, IMR-32 and SK-N-BE(2) cells were exposed to various concentrations of l-glutamate, which was either reconstituted in HCl (1 M) or post re-equilibrated to the pH of the culture medium (7.5). After 24 and 48 h of incubation, changes in the cell viability of treated versus untreated cells were evaluated. The effect of an identical amount of HCl present in the l-glutamate dilutions on neuroblastoma cell survival was also investigated. Our data showed that the neurotoxicity of glutamate reconstituted in HCl was comparable to that of HCl alone. Moreover, the pH variations induced by glutamate or HCl in the culture medium were similar. When the pH of the glutamate stock solution was re-equilibrated, l-glutamate induced variation in cell viability to a lower extent and after a longer incubation time. This study demonstrated that HCl used to reconstitute l-glutamate powder might alter the effect of glutamate itself in neuroblastoma cell cultures. Thus, this information might be useful to scientists who use l-glutamate to induce excitotoxicity or to test neuroprotective agents.