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U. O'Colmain, C. O'Brien, B.J. Harvey; Novel Non–Genomic Signalling Stimulated by Aldosterone in Human Ciliary Body Non–Pigmented Epithelium . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2085.
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Purpose:Steroid hormones exert rapid non–genomic effects in a variety of epithelia, often resulting in a change in the secretory or absorptive capacity of the tissue. These functional changes are effected by activation of intracellular second messenger systems and membrane ion transport. We have shown evidence for a local Renin–Angiotensin–Aldosterone–System in human non–pigmented epithelial (HNPE) cells1. Rapid effects of aldosterone on membrane ion transport have been shown to be mediated by Protein Kinase C (PKC) and intracellular calcium [Ca++]i in other tissues2. Methods:In this study, we investigated rapid effects of aldosterone on Protein Kinase A (PKA) , the alpha isoform of PKC (PKCα), Mitogen Activated Kinases (MAPK) and intracellular calcium and pH in HNPE cells. Results:Physiological concentrations of aldosterone (1nM) caused a rapid (<2mins) phosphorylation of PKA as measured using a fluorescent assay (Promega) . Western blotting revealed a rapid (<2mins) phosphorylation of MAPK in response to aldosterone whilst activation of PKCα occurred some minutes later. These responses were transient, with activation extinguished after 20 minutes. Preliminary results using spectrofluorescence single cell imaging demonstrate an increase in intracellular Ca2+ and pHi induced within minutes of treatment with aldosterone. Conclusions: These data demonstrate, for the first time, rapid responses to aldosterone in human ocular ciliary body epithelium. The signalling pathways affected are known regulators of epithelial electrolyte secretion and may have important implications in rapid regulation of aqueous humor secretion.1. Cullinane AB. et al. Renin angiotensin system expression and secretory function in cultured human ciliary body non–pigmented epithelium. Br J Ophthalmol. 2002, 86(6): 676–83 2. Maguire D. et al. Rapid Responses to Aldosterone in Human Distal Colon. Steroids 64 (1999), 51–63
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