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P Hoyng, A Schneemann, W Kamphuis; Immunolocalisation of Prostanoid EP Receptor Subtypes in Human Trabecular Meshwork . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1034.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To assess the localization of the EP type receptors and the relationship between the spatial distribution of the EP receptors and α smooth muscle actin in the human trabecular meshwork. Methods:Cryosections of human anterior segments from 9 different donors were immunostained using specific antibodies against the EP1, EP2, EP3α, EP4 receptor subtypes, and a smooth muscle actin. Human and rat retinas were stained with the EP1, EP2, EP3α, EP4 receptor antibodies, to test the specificity of the antibodies. Real-time PCR was applied to determine the relative gene expression levels of EP3α. Results:Antibodies against the EP1, EP3α, and EP4 receptor showed no detectable staining patterns whereas the antibody against the EP2 receptor revealed a clear staining of trabecular cells, but not of the inner wall of Schlemm's canal. The intensity of the EP2 receptor immunostaining decreased with increasing age of the donor. A clear co-localization between the EP2 receptor and α smooth muscle actin could not be established. Differential staining patterns were found EP1-4 receptors in human and rat retina.Conclusion:It is concluded that the EP2 receptor is the most abundant subtype of the PGE receptors present in the trabecular meshwork, plausibly responsible for the previously observed increase in outflow and the intraocular pressure lowering effects of PGE2 and PGE1. The mechanism underlying the contractile responses of the trabecular meshwork to EP2 receptor agonists,and the precise mechanism of the flow enhancement, are not explained by a close spatial association of the EP2 receptor and actin fibers.
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