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C.A. Opere, M. Zhao, H. Liu, C.J. Destache, R. Zeyssig, E.M. Monjok, G.E. Kouamou, S.E. Ohia; Regulation of Mammalian Retinal Catecholamine Levels by 8–IsoPGF2 and 8–IsoPGE2 . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2613.
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We have evidence that isoprostanes can modulate the release of excitatory amino acid neurotransmitters from isolated bovine retinae (Opere et al., Neurochem. Res.30:2005).
(1) To determine the effect of 8–iso–prostaglandin (PG)F2α and 8–isoPGE2 on catecholamine levels in bovine retinae, ex vivo and (2) examine the effect of 8–isoPGE2 on catecholamine concentrations in porcine retinae, in vitro.
Isolated bovine eyeballs were injected with isoprostane or vehicle intravitreally. After 30 mins of incubation, retina and vitreous humor were isolated and prepared for HPLC–ED studies. For in vitro studies, isolated porcine neural retina was incubated in Krebs solution containing different concentrations of 8–isoPGE2 (1 – 100 µM) for 15 minutes. After incubation, catecholamines in tissue homogenates and media were extracted with 0.2 N HClO4 and assayed by HPLC–ED.
In the concentration range, 1 nM to 10µM, intravitreally administered 8–isoPGF2α increased dopamine and norepinephrine levels in bovine retinae, ex vivo. For instance, 8–isoPGF2α (1 nM) increased dopamine and norepinephrine concentrations by 52 % (p<0.05) and 75 % (p<0.01), respectively. At 10 µM, 8–isoPGF2α also increased the levels of catecholamine metabolites, 3,4–dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) by 20% and 50 %, respectively. 8–isoPGE2 (0.1 and 10 µM) increased dopamine levels in bovine retinae by 68.75% (p<0.05) and 80.30% (p<0.01), respectively. In contrast, 8–isoPGE2 (0.1 µM) decreased the levels of DOPAC by 50%. In isolated porcine retinae, 8–isoPGE2 (1 – 100 µM) decreased norepinephrine levels but had no significant (P > 0.05) action on dopamine concentrations.
We conclude that isoprostanes can modulate catecholamine concentrations in mammalian retinae both ex vivo and in vitro. There is species difference in the response of the retina to 8–isoPGE2.
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