Distinct glycolysis inhibitors determine retinal cell sensitivity to glutamate-mediated injury

In this study, we analyzed how distinct glycolysis inhibitors influenced th e redox status of retinal cells, used as a neuronal model. Three different approaches were used to inhibit glycolysis: the cells were submitted to iod oacetic acid (IAA), an inhibitor of glyceraldehyde 3-phosphate dehydrogenas e, to 2-deoxy-glucose (DG) in glucose-free medium, which was used as a subs titute of glucose, or in the absence of glucose. The redox status of the ce lls was evaluated by determining the reduction of MTT (3-(4,5 -dimethylthia zol-2-yl)-2,5-diphenyl tetrazolium bromide). By the analysis of dose-respon se curves of MTT reduction, IAA showed values of IC50 = 7.02 x 10(-5) M, wh ereas DG showed values of IC50 = 7.42 x 10(-4) M. Upon 30 min-incubation, g lucose deprivation, per se, did not significantly affect MTT reduction. We also evaluated the reduction of MTT as an indicator of cell injury by expos ing the cells to 100 mu M glutamate during the decrement of glycolysis func tion. In the presence of glutamate, for 2 h, there was a decrease in MTT re duction, which was potentiated in the presence of DG (10-20% decrease), in the presence of IAA (about 30% decrease) or in glucose-free medium (about 3 0% decrease). Major changes observed by the MTT assay, upon exposure to glu tamate, indicative of changes in the redox status of retinal cells, were co ncomitant with variations in intracellular ATP. Under glucose deprivation, endogenous ATP decreased significantly from 38.9 +/- 4.4 to 13.3 +/- 0.7 nm ol/mg protein after exposure to 100 mu M glutamate. The results support a d ifferent vulnerability of retinal cells after being exposed to distinct for ms of glycolysis inhibition.