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Musa Kaya, Line Petersen, Toke Bek; The effects of nitroglycerine and COX-inhibition on retinal vessel diameters during hypoxia. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):698.
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Retinal hypoxia with consequent changes in blood flow play a role in a number of vision threatening diseases, such as diabetic retinopathy. Previous studies have shown that inhibition of nitric oxide synthase (NOS) and cyclooxygenase (COX) products are involved in hypoxia-induced dilatation of the retinal vessels. The aim of this study was to examine the effect of an NO donor and COX inhibition on the diameter regulation of retinal vessels during hypoxia in healthy subjects.
Twenty healthy subjects (17 males, 3 females) aged 20-47 years were examined. The Dynamic Vessel Analyzer (DVA) was used to measure retinal vessel diameters at rest, during isometric exercise and during flicker stimulation. The measurements were performed during normoxia and hypoxia before and after sublingual administration of the NO donor nitroglycerine, and were repeated on a second study day after topical administration of the COX-inhibitor diclofenac.
The resting diameter of the arterioles and venules increased significantly during hypoxia alone and in combination with nitroglycerine (p<0.0001). Hypoxia alone and combined with nitroglycerine significantly reduced both the arteriolar contraction during isometric exercise, and the dilatation of the arterioles and venules during flicker stimulation (p<0.0001). Diclofenac significantly reduced the arteriolar contraction during isometric exercise (p=0.005) and significantly increased the flicker-induced dilatation of the venules (p=0.03).
Diameter regulation of retinal vessels during hypoxia in healthy persons are affected by the inhibition of COX products, but not by increasing the NO concentration. The findings indicate that the vasodilating effect of NO is saturated in normal persons.
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