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Line Pedersen, Toke Bek; NO and COX products are involved in hypoxia-induced dilatation of retinal vessels in vivo. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4358.
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Retinal hypoxia with consequent changes in the blood perfusion is a central feature in the most common vision threatening diseases. The aim of this study was to examine the effects of inhibiting cyclo-oxygenase (COX) and NO-synthesis on hypoxia-induced relaxation of retinal vessels in humans.
Twenty healthy persons aged 20-55 years were examined on two study days separated by 4-7 days. The resting diameter and the diameter response secondary to isometric exercise and flicker stimulation of retinal vessels were studied using the Dynamic Vessel Analyzer (DVA) before and during breathing of a hypoxic gas mixture. The examinations were performed before and during intravenous infusion with the NOS inhibitor L-NMMA and were repeated on the second day after administration of the COX-inhibitor diclofenac eye drops.
Hypoxia induced a significant increase in the resting diameter of arterioles and venules (p<0.0001) which was reversed by the infusion of L-NMMA. Diclofenac significantly reduced arteriolar contraction induced by isometric exercise (p=0.04), whereas hypoxia significantly reduced L-NMMA induced contraction of retinal venules (p=0.0005). Flicker-induced dilatation of retinal arterioles was increased by L-NMMA (p<0.0001) whereas dilatation of retinal venules was significantly reduced during hypoxia and was reversed by L-NMMA (p<0.0001).
Diameter changes of retinal vessels during hypoxia are influenced by NO and COX products. This may point to new treatment strategies for diseases characterized by retinal hypoxia and disturbances in retinal perfusion.
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