Arachidonic acid metabolites and peroxide-induced inhibition of [ ³H]D-aspartate release from bovine isolated retinae

We have previously shown that hydrogen peroxide (H₂O ₂) can inhibit K⁺-depolarization-evoked [ ³H]D-aspartate release from bovine isolated retinae. In the present study, we investigated the role of arachidonic acid metabolites in the inhibitory response elicited by H₂O₂ in the bovine retinae. Furthermore, we examined the direct effect of H₂O ₂ on the production of prostaglandins and isoprostanes in this tissue. Isolated bovine retinae were prepared for studies of [ ³H]D-aspartate release using the Superfusion Method. Release of [³H]D-aspartate was elicited by Krebs solution containing an iso-osmotic concentration of KCl (50 mM). A direct action of H₂O ₂ on prostaglandin E₂ (PGE2) and 8-isoprostane F _2α (8-iso-PGF_2α) was also measured by enzyme-linked immunosorbant assay (ELISA). The cyclooxygenase inhibitor, flurbiprofen (3 μM), or the thromboxane-receptor antagonist, SQ 29548 (10 μM) had no significant (p > 0.05) effect on K⁺-evoked [ ³H]D-aspartate release. On the other hand, both flurbiprofen (3 μM) and SQ 29548 (10 μM) blocked the inhibition of K⁺-evoked [³H]D-aspartate induced by H₂O₂ (30 μM). In concentrations up to 100 μM, H₂O₂ caused an increase in PGE² and 8-iso-PGF_2α over basal levels. For instance, H₂O₂ (100 μM) increased PGE₂ and 8-iso-PGF_2α over basal levels by 348 ± 41% and 185 ± 26 (n = 4), respectively. We conclude that the peroxide-mediated inhibition of [³H]D-aspartate may involve the production of prostaglandins and isoprostanes in the bovine isolated retinae.