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Maria S. Torring, Simon M. Pedersen, Christian Aalkjaer, Toke Bek; The Contractile Response of Porcine Retinal Arterioles In Vitro Decreases with Increasing Branching Level of the Vessels. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6043.
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Disturbances in the diameter regulation of retinal arterioles are involved in the pathogenesis of retinal vascular disease. Hitherto, studies of diameter regulation have largely been performed on larger retinal arterioles, but recent evidence suggests that the smaller retinal arterioles are also involved in flow regulation and that mechanisms responsible for the regulation in these arterioles differ from those of the larger arterioles. Therefore, a method was developed for comparing the diameter regulation of smaller and larger retinal arterioles.
A special tissue chamber was designed for mounting and perfusing a whole segment of the porcine retina from the arteriole through the capillary system to the venule. A camera was connected to an inverted microscope for video recording of changes in the diameter of 1st, 2nd, 3rd and 4th order arterioles, and experiments were conducted to study the contractile effect of the prostaglandin analogue U46619, Endothelin-1, and phosphate buffer with high potassium (KPSS) on these arteriolar branching levels.
All three compounds reduced the diameter of retinal arterioles, and the relative diameter change was significantly larger in larger arterioles than in their smaller counterparts (p = 0.036). The diameter change for 1st order arterioles was most pronounced for KPSS (60+/-6%), was less pronounced for Endothelin-1 (55+/-14%), and was least pronounced for U46619 (17+/-22%).
Compounds known to contract larger retinal vessels have less contractile power on smaller retinal arterioles. Retinal vessels with different diameter may contribute differently to the regulation of retinal blood flow.
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