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Arnar Ossur Hardarson, Saevar Ingthorsson, Thor Eysteinsson; Localization of AT1 and MAS receptors on porcine retinal arteries. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3002.
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© 2017 Association for Research in Vision and Ophthalmology.
Inhibition of the renin-angiotensin system (RAS) is a promising way of reducing the progression of glaucoma, diabetic retinopathy and age-related macular degeneration. Both AT1 and MAS receptors play key roles in RAS. As porcine retinas are used to study retinal vascular functions, the purpose of this work was to determine whether AT1 and MAS receptors are present in the porcine retinal vasculature, and if so where they are located.
Freshly slaughtered porcine eyes were obtained from a local abattoir. Retinal vascular segments (2-12mm in length) were fixed with 3.7 % phosphate-buffered paraformaldehyde and incubated with primary antibodies against AT1 and MAS. To determine their location in/on the vascular segments primary antibodies against alpha smooth muscle actin and glial fibrillary acidic protein were used for reference. After wash the rings were incubated with secondary antibodies and 4’6-diamidino-2-phenylindole (DAPI) prior to examination. Immunofluorescent signals were viewed using a confocal laser scanning microscope.
AT1 receptors were identified in all samples tested (N=13), as were MAS receptors in separate samples (N=13). Both AT1 and MAS receptors were present in all samples outside the vascular smooth muscle layer and within the astrocyte layer (tunica media) (N=26). In < 10% of the samples were AT1 (N=1) and MAS (N=2) found present within the smooth muscle cell layer, i.e. the endothelium. Control experiments (N=12) were done to eliminate autofluorescence, and ensure the secondary antibodies were specific to only the primary antibodies. When whole retinal arteries were examined from the optic disk to the retinal periphery we found that the distribution and density of both AT1 (n=1) and MAS (n=1) varied along the vessels.
The study demonstrates for the first time the presence of AT1 and MAS in porcine retinal arteries, and that these receptors are colocalized on the same cellular layers of the retinal vasculature. In most cases the receptors are found outside the vascular smooth muscle layer and are rarely seen on the endothelium. This is in contrast to prior studies, where AT1 has mainly been found on the smooth muscle layer and endothelium.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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