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P. D. Senanayake, J. Drazba, M. E. Rayborn, K. G. Shadrach, J. G. Hollyfield; Localization of Angiotensin-(1-7) and Angiotensin II in Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1387.
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Angiotensin converting enzyme inhibitors and angiotensin receptor antagonists may reduce the progression of proliferative diabetic retinopathy. The balance between angiotensin (Ang II) and Ang-(1-7) could be the key factor in the implied role for Ang II in the pathogenesis of retinopathy. The objective of this study was to evaluate the distribution of Ang II and Ang-(1-7) in retina from mice, rats and human donor retina
Diabetic and non-diabetic donor human eyes were obtained from the Cleveland Eye Bank within 12 hours postmortem. Mice and rats (WKY and spontaneously hypertensive, SHR) were sacrificed by carbon dioxide asphyxiation. The eyes were enucleated and fixed in PBS- paraformaldehyde. Localization of Ang II and Ang-(1-7) was determined by paraffin sections using a commercial antibody for Ang II (Phoenix H-200-12) and an in-house antibody for Ang-(1-7) (CCF-Core 1). Since both primary antisera were polyclonal rabbit antisera, Ang II and Ang-(1-7) were probed on separate sections. Antibody binding was resolved with anti-rabbit Alexa 488 secondary antiserum. Specificity of the immunostaining was verified by substituting the primary antibodies with equivalent dilution of the non-immune IgG. Slides were mounted in anti-fade medium containing DAP1. A confocal laser-scanning microscope was used for immunoflorescence analysis.
Both Ang II and Ang-(1-7) antisera labeled Müller cells throughout all retinal layers, although the staining intensities were different. Ang (1-7) was more prominent. In the SHR rats Ang II was increased while Ang-(1-7) was similar in the two groups. In the non-diabetic regional differences were noted for Ang (1-7) in the human retina. In the peripheral retina but not in the macular region, Ang II immunoreactivity was marked in the Müller cell endfeet, in addition to the cellular processes spanning the retina. In contrast to retina from non-diabetic donor, the tissue from a hypertensive diabetic donor revealed a pronounced increase in labeling intensity for both Ang II and Ang-(1-7) in Müller cell endfeet.
Ang II and Ang-(1-7) are both localized in Müller cells. Ang-(1-7) is considered as the endogenous antagonist of Ang II. This study has demonstrated that the two peptides are ideally located to serve this function efficiently.
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