Effect of Peroxides on [³H]D-Aspartate Release from Bovine Isolated Retinae

In the present study, we investigated the effect of naturally occurring and synthetic peroxides on K⁺-depolarization-evoked release of [ ³H]D-aspartate from bovine isolated retinae. Furthermore, effect of peroxides on endogenous glutamate concentrations were measured by HPLC in bovine neural retinae and vitreous humor of eyes treated with hydrogen peroxide (H₂O₂) ex vivo. Both naturally occurring H ₂O₂ (1-100 μM) and synthetic (cumene hydroperoxide, cuOOH; 1-100 μM) peroxides caused a concentration-dependent inhibition of K⁺-evoked [³H]D-aspartate release without affecting basal tritium efflux. The antioxidant, trolox (2 mM) prevented the inhibition of evoked [³H]D-aspartate overflow elicited by both H₂O ₂ (30 μM) and cuOOH (10 μM). Inhibition of catalase by 3-amino-triazole (3- AT 100 mM) enhanced an inhibitory effect of a low concentration of H₂O₂ (1 μM) but antagonized the effect of H₂O₂ (30 μM) on K⁺-induced [ ³H]D-aspartate release. In ex vivo experiments, exogenously applied H₂O₂ (1-100 μM) also caused a concentration-related decrease in glutamate levels in the bovine retina. We conclude that peroxides can inhibit K⁺-evoked release of [³H]D-aspartate and also decrease endogenous glutamate concentrations in the bovine retina.