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R. Diederen, E.C. La Heij, J. de Vente, M. Markerink, A. Kijlstra, F. Hendrikse; Cyclic GMP Metabolism in Retinal Pigment Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3048.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Retinal pigment epithelial (RPE) cells play an essential role in the pathogenesis of various retinal diseases, like in proliferative vitreoretinopathy following retinal detachment. Previously, retinal detachment has been found to be associated with a decrease in the cGMP concentration in subretinal fluid as compared to controls (La Heij et al, Br J Ophthalmology, 2003). The source of cGMP in subretinal fluid is unknown, as is the reason for the decrease in cGMP concentration after retinal detachment. In this study we investigated cGMP production by particulate and soluble guanylyl cyclases (GCs) and cGMP breakdown by phosphodiesterases (PDEs) in human RPE cells. Methods: Cyclic GMP production was evaluated by immunocytochemistry and radioimmunoassay following culture of RPE cells in the presence of PDE inhibitors (IBMX,noselective; sildenafil,PDE 5 or BAY 60–7550, PDE 2) and/or guanylyl cyclase stimulators such as sodium nitropusside (SNP) or atrial natriuretic peptide (ANP). RPE cells were also stained for iNOS, nNOS and the α–2 and ß–1 subunits of soluble GC. In situ hybridization was performed to detect PDEs 2, 5 and 9 mRNA expression in RPE cells. Results: In the cultured human RPE cells, we found that soluble GC can be stimulated with SNP and particulate GC can be activated with ANP, resulting in increased cGMP production. The cGMP production by RPE cells was mainly initiated by stimulation of particulate GC (ANP: 93.2 pmol cGMP vs. SNP: 0.45 pmol cGMP per mg/protein). These radioimmunoassay data were confirmed by the data obtained by the immunocytochemisty. In addition, all cells stained immunopositive for the α–2 and ß–1 subunits of soluble GC, as well as for iNOS and nNOS. Messenger RNA of PDEs 2,5 and 9 could be detected in RPE cells. Conclusions: ltured human RPE cells are capable of producing cGMP after stimulation of both soluble and particulate GCs. Although more cGMP is formed by stimulation of particulate GC by ANP compared to stimulation of soluble GC. Activity of iNOS in normal PRE cells may be the source of nitric oxide, keeping the cGMP concentration at a basal level.
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