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

Abstract

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