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Abstract #8785 Published in IGR 5-1
Serum- and glucocorticoid-regulated kinase isoform-1 and epithelial sodium channel subunits in human ocular ciliary epithelium
Rauz S; Walker EA; Hughes SV; Coca-Prados M; Hewison M; Murray PI; Stewart PMInvestigative Ophthalmology and Visual Science 2003; 44: 1643-1651
PURPOSE: In peripheral sodium-transporting tissues, the serum- and glucocorticoid-regulated kinase (SGK) isoform-1 is an early corticosteroid target gene in the activation of epithelial sodium channels (ENaCs). Sodium transport across the human ocular nonpigmented and pigmented ciliary epithelial bilayer (NPE-PE) is essential for aqueous humor production, but the expression of SGK1 and ENaC subunits remain to be defined. METHODS: SGK1 and ENaC subunits were evaluated by in situ hybridization and RT-PCR analysis on human NPE-PE sections and an NPE cell line (ODM-2). Northern blot analyses were conducted on ODM-2 cells incubated with dexamethasone (DEX) or aldosterone (ALDO) and RU38486 (a glucocorticoid receptor (GR) antagonist) or RU26752 (a mineralocorticoid receptor (MR) antagonist) or both inhibitors. The affinity of the GRs and MRs for DEX and ALDO was assessed by radioligand-binding assays. RESULTS: Expression of SGK1 and ENaC subunits was confirmed in NPE-PE tissues and ODM-2 cells. Dose-dependent induction of SGK1 mRNA in the ODM-2 cells was demonstrated after incubation with DEX or ALDO. While response to DEX was not inhibited by RU38486 or RU26752, there was a moderate reduction in induction by ALDO in the presence of RU26752 that was completely abolished in the presence of both inhibitors. Specific binding of 3[H]DEX and 3[H]ALDO was established, revealing greater expression of GRs than MRs. CONCLUSIONS: The expression of ENaCs within the NPE-PE and corticosteroid regulation of SGK1 through the GR and MR, indicate that this mechanism may be a feature of sodium transport in the human ocular ciliary epithelium.
Dr. S. Rauz, Academic Unit of Ophthalmology, Division of Immunity and Infection, University of Birmingham, Birmingham, UK
Classification:
2.9 Ciliary body (Part of: 2 Anatomical structures in glaucoma)
3 Laboratory methods
