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J. M. Stine, K. N. Gelatt, C. Roberts, P. A. Lewis, K. P. Barrie, M. E. Kallberg, D. A. Samuelson; Immuno-Localization of Glucocorticoid Receptors Along the Aqueous Pathway of Dogs With POAG. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2082.
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For some time it has been known that individuals with primary glaucoma have increased sensitivity to glucocorticoids (GC). More recent techniques have allowed researchers to reveal a widespread expression of glucocorticoid receptors (GCRs) in the eye, suggesting the important function GC have in ocular health. We have begun to study the presence of both the glucocorticoid receptors and their prereceptors in the eyes of beagles with primary-open angle glaucoma (POAG) and age-matched normals by immuno-localization.
Paraffin-embedded specimens from the anterior uveas of 14 Beagles with inherited glaucoma (1-day to 13-yrs-old) and age-matched normal Beagles were sectioned and incubated with anti-human GCR (alpha isoform) or 11 beta-hydroxysteroid dehydrogenase type 1 (11bHSD1) polyclonal rabbit antibodies. 11bHSD1 is a prereceptor that regenerates active GCs and thus amplifies local CG action. Specimens were incubated with secondary antibody with biotinylated link followed by peroxidase-labeled streptavidin and then by substrate-chromogen for light microscopy.
Within normal canine specimens, cells of the nonpigmented epithelium (NPE) of the CB processes stained weakly and diffusely for both GCR and 11bHSD1 within their cytoplasm, being strongest in the adults. Among the glaucomatous dogs, the reaction for GCR and 11bHSD1 in the NPE was considerably more intense and localized than the age-matched normals, especially among the Beagles with earlier stages of POAG and prior to IOP elevation. Within the normal iridocorneal angle (ICA), the trabecular meshwork reacted positively for GCR with little age-related differences. Within the eyes of the moderate and advanced POAG Beagles, GCR localization within the ICA and adjacent region was greater than that of age-matched normals. 11bHSD1 localization was not observed within ICAs of normal eyes but seen among affected animals, having been most pronounced during moderate stages of the disease and intensely present within the corneal endothelium.
Immuno-localization of both GCR and 11bHSD1 was successfully observed in both the normal and glaucomatous canine eye. Changes in the apparent activity of GCR and 11bHSD1 within the aqueous humor outflow pathway of individuals with spontaneous glaucoma occurred prior to disease expression and continued during its progression. The potential differential responsiveness of GCRs in this glaucomatous model may help to understand what role GCs possess in the development of spontaneous glaucomas.
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