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S.E. Ohia, A.M. LeDay, K.H. Kulkarni, C.A. Opere; Role of Arachidonic Acid Metabolites in Peroxide-Induced Inhibition of [3H]D-Aspartate Release from Bovine Isolated Retinae . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2082.
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We have previously shown that hydrogen peroxide (H2O2) can inhibit potassium (K+)-depolarization evoked [3H]D-aspartate release from bovine isolated retinae (Exp. Eye Res. 71: abs. no. 386, 2000). Purpose: To study the role of two arachidonic acid metabolites, prostaglandins and isoprostanes, in the inhibitory response induced by peroxides on [3H]D-aspartate from isolated bovine retinae. Method: Isolated neural retinae were incubated in oxygenated Krebs solution containing 200nM of [3H]D-aspartate for 60 mins and then prepared for studies of neurotransmitter release using the superfusion method. Release of [3H]D-aspartate was evoked by iso-osmotic concentration of K+(50 mM) stimuli applied at 80-88 mins and 116-124 mins after the onset of superfusion. A direct action of H2O2 on retinal PGE2 and 8-iso-PGF2a production was measured by ELISA methods. Results: The cyclooxygenase inhibitor, flurbiprofen (3 µM) or the isoprostane receptor antaganonist, SQ 29,548 (10 µM) had no significant (p>0.05) effect on K+-evoked [3H]D-aspartate release. However, pretreatment of tissues with flurbiprofen abolished the inhibitory response elicited by H2O2 (30 µM) on K+-evoked [3H]D-aspartate release. Blockade of isoprostane receptors with SQ 29548 caused a reversal of the H2O2 induced inhibition of the K+ response. In concentrations up to 100 µM, H2O2 increased retinal PGE2 and 8-iso-PGF2a concentrations over basal levels. For instance, H2O2 (100 µM) increased PGE2 and 8-iso-PGF2a concentrations by 350% and 190%, respectively. Conclusion: We conclude that prostaglandins and isoprostanes mediate peroxide-induced inhibition of K+-evoked [3H]D-aspartate release from the bovine retina.
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