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TG Papadaki, A Vasilaki, M Tsilimbaris, I Pallikaris, K Thermos; Somatostatin Regulates Nitric Oxide Production in Human Retinal Pigment Epithelial (RPE) Cell Cultures . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4584.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Somatostatin is a modulator of retinal circuitry, but its role in the retina and the RPE is currently under investigation. The aim of the present study was to determine the presence of somatostatin, the localization of its receptors (ssts) and their possible involvement in the regulation of nitric oxide production in human RPE cultures, as was previously shown in retinal explants [Vasilaki et al., Abs Soc Neurosci, 2001]. Methods: Somatostatin levels were detected by radioimmunoassay. Polyclonal antibodies raised against sst receptors were applied to the human RPE cultures (ARPE -19), while NADPH-diaphorase staining was assessed histochemically. The ability of somatostatin and selective sst analogs to influence the production of nitric oxide was assessed by examining the production of its stable metabolites NO2- and NO3-. Results: SRIF (0.71 0.21pmoles/mg protein) and its receptors sst2B and sst4 were detected in human RPE cultures, as was NADPH-diaphorase staining. Somatostatin increased the levels of nitric oxide metabolites and this effect was mimicked only by an sst2 selective ligand Conclusions: The presence of somatostatin and its receptors, sst2B and sst4, suggests an autocrine or paracrine role for somatostatin. Its ability to regulate nitric oxide production, by activating sst2B, provides for the first time a functional role of somatostatin in the RPE. This may involve the maintenance of homeostasis of the outer retina and the regulation of the blood-eye barrier.
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